June 2020 - Linux-stable-mirror

FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

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FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

4 years, 8 months

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0
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FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

4 years, 8 months

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0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 5.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world" failed to apply to 5.7-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.7-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d308a881a5917bdb46472c861a1dabe54b46c423 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 24 Apr 2020 14:13:08 -0400 Subject: [PATCH] drm/dp_mst: Kill the second sideband tx slot, save the world While we support using both tx slots for sideband transmissions, it appears that DisplayPort devices in the field didn't end up doing a very good job of supporting it. From section 5.2.1 of the DP 2.0 specification: There are MST Sink/Branch devices in the field that do not handle interleaved message transactions. To facilitate message transaction handling by downstream devices, an MST Source device shall generate message transactions in an atomic manner (i.e., the MST Source device shall not concurrently interleave multiple message transactions). Therefore, an MST Source device shall clear the Message_Sequence_No value in the Sideband_MSG_Header to 0. This might come as a bit of a surprise since the vast majority of hubs will support using both tx slots even if they don't support interleaved message transactions, and we've also been using both tx slots since MST was introduced into the kernel. However, there is one device we've had trouble getting working consistently with MST for so long that we actually assumed it was just broken: the infamous Dell P2415Qb. Previously this monitor would appear to work sometimes, but in most situations would end up timing out LINK_ADDRESS messages almost at random until you power cycled the whole display. After reading section 5.2.1 in the DP 2.0 spec, some closer investigation into this infamous display revealed it was only ever timing out on sideband messages in the second TX slot. Sure enough, avoiding the second TX slot has suddenly made this monitor function perfectly for the first time in five years. And since they explicitly mention this in the specification, I doubt this is the only monitor out there with this issue. This might even explain explain the seemingly harmless garbage sideband responses we would occasionally see with MST hubs! So - rewrite our sideband TX handlers to only support one TX slot. In order to simplify our sideband handling now that we don't support transmitting to multiple MSTBs at once, we also move all state tracking for down replies from mstbs to the topology manager. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: "Lin, Wayne" <Wayne.Lin(a)amd.com> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200424181308.770749-1-lyude… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index d2c19791b2b6..b90cca361afe 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -1197,16 +1197,8 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, /* remove from q */ if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED || - txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) { + txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) list_del(&txmsg->next); - } - - if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND || - txmsg->state == DRM_DP_SIDEBAND_TX_SENT) { - mstb->tx_slots[txmsg->seqno] = NULL; - } - mgr->is_waiting_for_dwn_reply = false; - } out: if (unlikely(ret == -EIO) && drm_debug_enabled(DRM_UT_DP)) { @@ -2685,22 +2677,6 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, struct drm_dp_mst_branch *mstb = txmsg->dst; u8 req_type; - /* both msg slots are full */ - if (txmsg->seqno == -1) { - if (mstb->tx_slots[0] && mstb->tx_slots[1]) { - DRM_DEBUG_KMS("%s: failed to find slot\n", __func__); - return -EAGAIN; - } - if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) { - txmsg->seqno = mstb->last_seqno; - mstb->last_seqno ^= 1; - } else if (mstb->tx_slots[0] == NULL) - txmsg->seqno = 0; - else - txmsg->seqno = 1; - mstb->tx_slots[txmsg->seqno] = txmsg; - } - req_type = txmsg->msg[0] & 0x7f; if (req_type == DP_CONNECTION_STATUS_NOTIFY || req_type == DP_RESOURCE_STATUS_NOTIFY) @@ -2712,7 +2688,7 @@ static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr, hdr->lcr = mstb->lct - 1; if (mstb->lct > 1) memcpy(hdr->rad, mstb->rad, mstb->lct / 2); - hdr->seqno = txmsg->seqno; + return 0; } /* @@ -2727,15 +2703,15 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, int len, space, idx, tosend; int ret; + if (txmsg->state == DRM_DP_SIDEBAND_TX_SENT) + return 0; + memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr)); - if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { - txmsg->seqno = -1; + if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; - } - /* make hdr from dst mst - for replies use seqno - otherwise assign one */ + /* make hdr from dst mst */ ret = set_hdr_from_dst_qlock(&hdr, txmsg); if (ret < 0) return ret; @@ -2788,42 +2764,17 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) if (list_empty(&mgr->tx_msg_downq)) return; - txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next); + txmsg = list_first_entry(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); ret = process_single_tx_qlock(mgr, txmsg, false); - if (ret == 1) { - /* txmsg is sent it should be in the slots now */ - mgr->is_waiting_for_dwn_reply = true; - list_del(&txmsg->next); - } else if (ret) { + if (ret < 0) { DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - mgr->is_waiting_for_dwn_reply = false; list_del(&txmsg->next); - if (txmsg->seqno != -1) - txmsg->dst->tx_slots[txmsg->seqno] = NULL; txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; wake_up_all(&mgr->tx_waitq); } } -/* called holding qlock */ -static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr, - struct drm_dp_sideband_msg_tx *txmsg) -{ - int ret; - - /* construct a chunk from the first msg in the tx_msg queue */ - ret = process_single_tx_qlock(mgr, txmsg, true); - - if (ret != 1) - DRM_DEBUG_KMS("failed to send msg in q %d\n", ret); - - if (txmsg->seqno != -1) { - WARN_ON((unsigned int)txmsg->seqno > - ARRAY_SIZE(txmsg->dst->tx_slots)); - txmsg->dst->tx_slots[txmsg->seqno] = NULL; - } -} - static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { @@ -2836,8 +2787,7 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr, drm_dp_mst_dump_sideband_msg_tx(&p, txmsg); } - if (list_is_singular(&mgr->tx_msg_downq) && - !mgr->is_waiting_for_dwn_reply) + if (list_is_singular(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -3457,7 +3407,7 @@ static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb, - int req_type, int seqno, bool broadcast) + int req_type, bool broadcast) { struct drm_dp_sideband_msg_tx *txmsg; @@ -3466,13 +3416,11 @@ static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr, return -ENOMEM; txmsg->dst = mstb; - txmsg->seqno = seqno; drm_dp_encode_up_ack_reply(txmsg, req_type); mutex_lock(&mgr->qlock); - - process_single_up_tx_qlock(mgr, txmsg); - + /* construct a chunk from the first msg in the tx_msg queue */ + process_single_tx_qlock(mgr, txmsg, true); mutex_unlock(&mgr->qlock); kfree(txmsg); @@ -3697,8 +3645,9 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr, } EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume); -static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, - struct drm_dp_mst_branch **mstb, int *seqno) +static bool +drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, + struct drm_dp_mst_branch **mstb) { int len; u8 replyblock[32]; @@ -3706,13 +3655,13 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, int ret; u8 hdrlen; struct drm_dp_sideband_msg_hdr hdr; - struct drm_dp_sideband_msg_rx *msg; + struct drm_dp_sideband_msg_rx *msg = + up ? &mgr->up_req_recv : &mgr->down_rep_recv; int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE; if (!up) *mstb = NULL; - *seqno = -1; len = min(mgr->max_dpcd_transaction_bytes, 16); ret = drm_dp_dpcd_read(mgr->aux, basereg, replyblock, len); @@ -3729,11 +3678,7 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, return false; } - *seqno = hdr.seqno; - - if (up) { - msg = &mgr->up_req_recv; - } else { + if (!up) { /* Caller is responsible for giving back this reference */ *mstb = drm_dp_get_mst_branch_device(mgr, hdr.lct, hdr.rad); if (!*mstb) { @@ -3741,7 +3686,6 @@ static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up, hdr.lct); return false; } - msg = &(*mstb)->down_rep_recv[hdr.seqno]; } if (!drm_dp_sideband_msg_set_header(msg, &hdr, hdrlen)) { @@ -3785,13 +3729,10 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_sideband_msg_tx *txmsg; struct drm_dp_mst_branch *mstb = NULL; - struct drm_dp_sideband_msg_rx *msg = NULL; - int seqno = -1; - - if (!drm_dp_get_one_sb_msg(mgr, false, &mstb, &seqno)) - goto out_clear_reply; + struct drm_dp_sideband_msg_rx *msg = &mgr->down_rep_recv; - msg = &mstb->down_rep_recv[seqno]; + if (!drm_dp_get_one_sb_msg(mgr, false, &mstb)) + goto out; /* Multi-packet message transmission, don't clear the reply */ if (!msg->have_eomt) @@ -3799,11 +3740,12 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) /* find the message */ mutex_lock(&mgr->qlock); - txmsg = mstb->tx_slots[seqno]; - /* remove from slots */ + txmsg = list_first_entry_or_null(&mgr->tx_msg_downq, + struct drm_dp_sideband_msg_tx, next); mutex_unlock(&mgr->qlock); - if (!txmsg) { + /* Were we actually expecting a response, and from this mstb? */ + if (!txmsg || txmsg->dst != mstb) { struct drm_dp_sideband_msg_hdr *hdr; hdr = &msg->initial_hdr; DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n", @@ -3828,8 +3770,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) mutex_lock(&mgr->qlock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; - mstb->tx_slots[seqno] = NULL; - mgr->is_waiting_for_dwn_reply = false; + list_del(&txmsg->next); mutex_unlock(&mgr->qlock); wake_up_all(&mgr->tx_waitq); @@ -3837,11 +3778,7 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) return 0; out_clear_reply: - mutex_lock(&mgr->qlock); - mgr->is_waiting_for_dwn_reply = false; - mutex_unlock(&mgr->qlock); - if (msg) - memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); + memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx)); out: if (mstb) drm_dp_mst_topology_put_mstb(mstb); @@ -3921,9 +3858,8 @@ static void drm_dp_mst_up_req_work(struct work_struct *work) static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) { struct drm_dp_pending_up_req *up_req; - int seqno; - if (!drm_dp_get_one_sb_msg(mgr, true, NULL, &seqno)) + if (!drm_dp_get_one_sb_msg(mgr, true, NULL)) goto out; if (!mgr->up_req_recv.have_eomt) @@ -3947,7 +3883,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr) } drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, up_req->msg.req_type, - seqno, false); + false); if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) { const struct drm_dp_connection_status_notify *conn_stat = @@ -4692,7 +4628,7 @@ static void drm_dp_tx_work(struct work_struct *work) struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work); mutex_lock(&mgr->qlock); - if (!list_empty(&mgr->tx_msg_downq) && !mgr->is_waiting_for_dwn_reply) + if (!list_empty(&mgr->tx_msg_downq)) process_single_down_tx_qlock(mgr); mutex_unlock(&mgr->qlock); } @@ -4713,26 +4649,25 @@ static inline void drm_dp_delayed_destroy_mstb(struct drm_dp_mst_branch *mstb) { struct drm_dp_mst_topology_mgr *mgr = mstb->mgr; - struct drm_dp_mst_port *port, *tmp; + struct drm_dp_mst_port *port, *port_tmp; + struct drm_dp_sideband_msg_tx *txmsg, *txmsg_tmp; bool wake_tx = false; mutex_lock(&mgr->lock); - list_for_each_entry_safe(port, tmp, &mstb->ports, next) { + list_for_each_entry_safe(port, port_tmp, &mstb->ports, next) { list_del(&port->next); drm_dp_mst_topology_put_port(port); } mutex_unlock(&mgr->lock); - /* drop any tx slots msg */ + /* drop any tx slot msg */ mutex_lock(&mstb->mgr->qlock); - if (mstb->tx_slots[0]) { - mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[0] = NULL; - wake_tx = true; - } - if (mstb->tx_slots[1]) { - mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT; - mstb->tx_slots[1] = NULL; + list_for_each_entry_safe(txmsg, txmsg_tmp, &mgr->tx_msg_downq, next) { + if (txmsg->dst != mstb) + continue; + + txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + list_del(&txmsg->next); wake_tx = true; } mutex_unlock(&mstb->mgr->qlock); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 96bcf33c03d3..9e1ffcd7cb68 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -194,11 +194,8 @@ struct drm_dp_sideband_msg_rx { * @rad: Relative Address to talk to this branch device. * @lct: Link count total to talk to this branch device. * @num_ports: number of ports on the branch. - * @msg_slots: one bit per transmitted msg slot. * @port_parent: pointer to the port parent, NULL if toplevel. * @mgr: topology manager for this branch device. - * @tx_slots: transmission slots for this device. - * @last_seqno: last sequence number used to talk to this. * @link_address_sent: if a link address message has been sent to this device yet. * @guid: guid for DP 1.2 branch device. port under this branch can be * identified by port #. @@ -239,7 +236,6 @@ struct drm_dp_mst_branch { u8 lct; int num_ports; - int msg_slots; /** * @ports: the list of ports on this branch device. This should be * considered protected for reading by &drm_dp_mst_topology_mgr.lock. @@ -252,20 +248,11 @@ struct drm_dp_mst_branch { */ struct list_head ports; - /* list of tx ops queue for this port */ struct drm_dp_mst_port *port_parent; struct drm_dp_mst_topology_mgr *mgr; - /* slots are protected by mstb->mgr->qlock */ - struct drm_dp_sideband_msg_tx *tx_slots[2]; - int last_seqno; bool link_address_sent; - /** - * @down_rep_recv: Message receiver state for down replies. - */ - struct drm_dp_sideband_msg_rx down_rep_recv[2]; - /* global unique identifier to identify branch devices */ u8 guid[16]; }; @@ -567,6 +554,12 @@ struct drm_dp_mst_topology_mgr { */ struct drm_dp_sideband_msg_rx up_req_recv; + /** + * @down_rep_recv: Message receiver state for replies to down + * requests. + */ + struct drm_dp_sideband_msg_rx down_rep_recv; + /** * @lock: protects @mst_state, @mst_primary, @dpcd, and * @payload_id_table_cleared. @@ -592,11 +585,6 @@ struct drm_dp_mst_topology_mgr { */ bool payload_id_table_cleared : 1; - /** - * @is_waiting_for_dwn_reply: whether we're waiting for a down reply. - */ - bool is_waiting_for_dwn_reply : 1; - /** * @mst_primary: Pointer to the primary/first branch device. */ @@ -621,13 +609,12 @@ struct drm_dp_mst_topology_mgr { const struct drm_private_state_funcs *funcs; /** - * @qlock: protects @tx_msg_downq, the &drm_dp_mst_branch.txslost and - * &drm_dp_sideband_msg_tx.state once they are queued + * @qlock: protects @tx_msg_downq and &drm_dp_sideband_msg_tx.state */ struct mutex qlock; /** - * @tx_msg_downq: List of pending down replies. + * @tx_msg_downq: List of pending down requests */ struct list_head tx_msg_downq;

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Increase ACT retry timeout to 3s" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 873a95e0d59ac06901ae261dda0b7165ffd002b8 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 3 Apr 2020 15:47:15 -0400 Subject: [PATCH] drm/dp_mst: Increase ACT retry timeout to 3s MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently we only poll for an ACT up to 30 times, with a busy-wait delay of 100µs between each attempt - giving us a timeout of 2900µs. While this might seem sensible, it would appear that in certain scenarios it can take dramatically longer then that for us to receive an ACT. On one of the EVGA MST hubs that I have available, I observed said hub sometimes taking longer then a second before signalling the ACT. These delays mostly seem to occur when previous sideband messages we've sent are NAKd by the hub, however it wouldn't be particularly surprising if it's possible to reproduce times like this simply by introducing branch devices with large LCTs since payload allocations have to take effect on every downstream device up to the payload's target. So, instead of just retrying 30 times we poll for the ACT for up to 3ms, and additionally use usleep_range() to avoid a very long and rude busy-wait. Note that the previous retry count of 30 appears to have been arbitrarily chosen, as I can't find any mention of a recommended timeout or retry count for ACTs in the DisplayPort 2.0 specification. This also goes for the range we were previously using for udelay(), although I suspect that was just copied from the recommended delay for link training on SST devices. Changes since v1: * Use readx_poll_timeout() instead of open-coding timeout loop - Sean Paul Changes since v2: * Increase poll interval to 200us - Sean Paul * Print status in hex when we timeout waiting for ACT - Sean Paul Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200406221253.1307209-4-lyud… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index e7a5bd3e6015..8942ab98ab64 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -27,6 +27,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/seq_file.h> +#include <linux/iopoll.h> #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) #include <linux/stacktrace.h> @@ -4438,43 +4439,53 @@ static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr, return ret; } +static int do_get_act_status(struct drm_dp_aux *aux) +{ + int ret; + u8 status; + + ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status); + if (ret < 0) + return ret; + + return status; +} /** * drm_dp_check_act_status() - Polls for ACT handled status. * @mgr: manager to use * * Tries waiting for the MST hub to finish updating it's payload table by - * polling for the ACT handled bit. + * polling for the ACT handled bit for up to 3 seconds (yes-some hubs really + * take that long). * * Returns: * 0 if the ACT was handled in time, negative error code on failure. */ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr) { - int count = 0, ret; - u8 status; - - do { - ret = drm_dp_dpcd_readb(mgr->aux, - DP_PAYLOAD_TABLE_UPDATE_STATUS, - &status); - if (ret < 0) { - DRM_DEBUG_KMS("failed to read payload table status %d\n", - ret); - return ret; - } - - if (status & DP_PAYLOAD_ACT_HANDLED) - break; - count++; - udelay(100); - } while (count < 30); - - if (!(status & DP_PAYLOAD_ACT_HANDLED)) { - DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", - status, count); + /* + * There doesn't seem to be any recommended retry count or timeout in + * the MST specification. Since some hubs have been observed to take + * over 1 second to update their payload allocations under certain + * conditions, we use a rather large timeout value. + */ + const int timeout_ms = 3000; + int ret, status; + + ret = readx_poll_timeout(do_get_act_status, mgr->aux, status, + status & DP_PAYLOAD_ACT_HANDLED || status < 0, + 200, timeout_ms * USEC_PER_MSEC); + if (ret < 0 && status >= 0) { + DRM_DEBUG_KMS("Failed to get ACT after %dms, last status: %02x\n", + timeout_ms, status); return -EINVAL; + } else if (status < 0) { + DRM_DEBUG_KMS("Failed to read payload table status: %d\n", + status); + return status; } + return 0; } EXPORT_SYMBOL(drm_dp_check_act_status);

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Increase ACT retry timeout to 3s" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 873a95e0d59ac06901ae261dda0b7165ffd002b8 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 3 Apr 2020 15:47:15 -0400 Subject: [PATCH] drm/dp_mst: Increase ACT retry timeout to 3s MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently we only poll for an ACT up to 30 times, with a busy-wait delay of 100µs between each attempt - giving us a timeout of 2900µs. While this might seem sensible, it would appear that in certain scenarios it can take dramatically longer then that for us to receive an ACT. On one of the EVGA MST hubs that I have available, I observed said hub sometimes taking longer then a second before signalling the ACT. These delays mostly seem to occur when previous sideband messages we've sent are NAKd by the hub, however it wouldn't be particularly surprising if it's possible to reproduce times like this simply by introducing branch devices with large LCTs since payload allocations have to take effect on every downstream device up to the payload's target. So, instead of just retrying 30 times we poll for the ACT for up to 3ms, and additionally use usleep_range() to avoid a very long and rude busy-wait. Note that the previous retry count of 30 appears to have been arbitrarily chosen, as I can't find any mention of a recommended timeout or retry count for ACTs in the DisplayPort 2.0 specification. This also goes for the range we were previously using for udelay(), although I suspect that was just copied from the recommended delay for link training on SST devices. Changes since v1: * Use readx_poll_timeout() instead of open-coding timeout loop - Sean Paul Changes since v2: * Increase poll interval to 200us - Sean Paul * Print status in hex when we timeout waiting for ACT - Sean Paul Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200406221253.1307209-4-lyud… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index e7a5bd3e6015..8942ab98ab64 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -27,6 +27,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/seq_file.h> +#include <linux/iopoll.h> #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) #include <linux/stacktrace.h> @@ -4438,43 +4439,53 @@ static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr, return ret; } +static int do_get_act_status(struct drm_dp_aux *aux) +{ + int ret; + u8 status; + + ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status); + if (ret < 0) + return ret; + + return status; +} /** * drm_dp_check_act_status() - Polls for ACT handled status. * @mgr: manager to use * * Tries waiting for the MST hub to finish updating it's payload table by - * polling for the ACT handled bit. + * polling for the ACT handled bit for up to 3 seconds (yes-some hubs really + * take that long). * * Returns: * 0 if the ACT was handled in time, negative error code on failure. */ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr) { - int count = 0, ret; - u8 status; - - do { - ret = drm_dp_dpcd_readb(mgr->aux, - DP_PAYLOAD_TABLE_UPDATE_STATUS, - &status); - if (ret < 0) { - DRM_DEBUG_KMS("failed to read payload table status %d\n", - ret); - return ret; - } - - if (status & DP_PAYLOAD_ACT_HANDLED) - break; - count++; - udelay(100); - } while (count < 30); - - if (!(status & DP_PAYLOAD_ACT_HANDLED)) { - DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", - status, count); + /* + * There doesn't seem to be any recommended retry count or timeout in + * the MST specification. Since some hubs have been observed to take + * over 1 second to update their payload allocations under certain + * conditions, we use a rather large timeout value. + */ + const int timeout_ms = 3000; + int ret, status; + + ret = readx_poll_timeout(do_get_act_status, mgr->aux, status, + status & DP_PAYLOAD_ACT_HANDLED || status < 0, + 200, timeout_ms * USEC_PER_MSEC); + if (ret < 0 && status >= 0) { + DRM_DEBUG_KMS("Failed to get ACT after %dms, last status: %02x\n", + timeout_ms, status); return -EINVAL; + } else if (status < 0) { + DRM_DEBUG_KMS("Failed to read payload table status: %d\n", + status); + return status; } + return 0; } EXPORT_SYMBOL(drm_dp_check_act_status);

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Increase ACT retry timeout to 3s" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 873a95e0d59ac06901ae261dda0b7165ffd002b8 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 3 Apr 2020 15:47:15 -0400 Subject: [PATCH] drm/dp_mst: Increase ACT retry timeout to 3s MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently we only poll for an ACT up to 30 times, with a busy-wait delay of 100µs between each attempt - giving us a timeout of 2900µs. While this might seem sensible, it would appear that in certain scenarios it can take dramatically longer then that for us to receive an ACT. On one of the EVGA MST hubs that I have available, I observed said hub sometimes taking longer then a second before signalling the ACT. These delays mostly seem to occur when previous sideband messages we've sent are NAKd by the hub, however it wouldn't be particularly surprising if it's possible to reproduce times like this simply by introducing branch devices with large LCTs since payload allocations have to take effect on every downstream device up to the payload's target. So, instead of just retrying 30 times we poll for the ACT for up to 3ms, and additionally use usleep_range() to avoid a very long and rude busy-wait. Note that the previous retry count of 30 appears to have been arbitrarily chosen, as I can't find any mention of a recommended timeout or retry count for ACTs in the DisplayPort 2.0 specification. This also goes for the range we were previously using for udelay(), although I suspect that was just copied from the recommended delay for link training on SST devices. Changes since v1: * Use readx_poll_timeout() instead of open-coding timeout loop - Sean Paul Changes since v2: * Increase poll interval to 200us - Sean Paul * Print status in hex when we timeout waiting for ACT - Sean Paul Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200406221253.1307209-4-lyud… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index e7a5bd3e6015..8942ab98ab64 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -27,6 +27,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/seq_file.h> +#include <linux/iopoll.h> #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) #include <linux/stacktrace.h> @@ -4438,43 +4439,53 @@ static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr, return ret; } +static int do_get_act_status(struct drm_dp_aux *aux) +{ + int ret; + u8 status; + + ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status); + if (ret < 0) + return ret; + + return status; +} /** * drm_dp_check_act_status() - Polls for ACT handled status. * @mgr: manager to use * * Tries waiting for the MST hub to finish updating it's payload table by - * polling for the ACT handled bit. + * polling for the ACT handled bit for up to 3 seconds (yes-some hubs really + * take that long). * * Returns: * 0 if the ACT was handled in time, negative error code on failure. */ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr) { - int count = 0, ret; - u8 status; - - do { - ret = drm_dp_dpcd_readb(mgr->aux, - DP_PAYLOAD_TABLE_UPDATE_STATUS, - &status); - if (ret < 0) { - DRM_DEBUG_KMS("failed to read payload table status %d\n", - ret); - return ret; - } - - if (status & DP_PAYLOAD_ACT_HANDLED) - break; - count++; - udelay(100); - } while (count < 30); - - if (!(status & DP_PAYLOAD_ACT_HANDLED)) { - DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", - status, count); + /* + * There doesn't seem to be any recommended retry count or timeout in + * the MST specification. Since some hubs have been observed to take + * over 1 second to update their payload allocations under certain + * conditions, we use a rather large timeout value. + */ + const int timeout_ms = 3000; + int ret, status; + + ret = readx_poll_timeout(do_get_act_status, mgr->aux, status, + status & DP_PAYLOAD_ACT_HANDLED || status < 0, + 200, timeout_ms * USEC_PER_MSEC); + if (ret < 0 && status >= 0) { + DRM_DEBUG_KMS("Failed to get ACT after %dms, last status: %02x\n", + timeout_ms, status); return -EINVAL; + } else if (status < 0) { + DRM_DEBUG_KMS("Failed to read payload table status: %d\n", + status); + return status; } + return 0; } EXPORT_SYMBOL(drm_dp_check_act_status);

4 years, 8 months

1
0
0 0

FAILED: patch "[PATCH] drm/dp_mst: Increase ACT retry timeout to 3s" failed to apply to 4.19-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 873a95e0d59ac06901ae261dda0b7165ffd002b8 Mon Sep 17 00:00:00 2001 From: Lyude Paul <lyude(a)redhat.com> Date: Fri, 3 Apr 2020 15:47:15 -0400 Subject: [PATCH] drm/dp_mst: Increase ACT retry timeout to 3s MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently we only poll for an ACT up to 30 times, with a busy-wait delay of 100µs between each attempt - giving us a timeout of 2900µs. While this might seem sensible, it would appear that in certain scenarios it can take dramatically longer then that for us to receive an ACT. On one of the EVGA MST hubs that I have available, I observed said hub sometimes taking longer then a second before signalling the ACT. These delays mostly seem to occur when previous sideband messages we've sent are NAKd by the hub, however it wouldn't be particularly surprising if it's possible to reproduce times like this simply by introducing branch devices with large LCTs since payload allocations have to take effect on every downstream device up to the payload's target. So, instead of just retrying 30 times we poll for the ACT for up to 3ms, and additionally use usleep_range() to avoid a very long and rude busy-wait. Note that the previous retry count of 30 appears to have been arbitrarily chosen, as I can't find any mention of a recommended timeout or retry count for ACTs in the DisplayPort 2.0 specification. This also goes for the range we were previously using for udelay(), although I suspect that was just copied from the recommended delay for link training on SST devices. Changes since v1: * Use readx_poll_timeout() instead of open-coding timeout loop - Sean Paul Changes since v2: * Increase poll interval to 200us - Sean Paul * Print status in hex when we timeout waiting for ACT - Sean Paul Signed-off-by: Lyude Paul <lyude(a)redhat.com> Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: Sean Paul <sean(a)poorly.run> Cc: <stable(a)vger.kernel.org> # v3.17+ Reviewed-by: Sean Paul <sean(a)poorly.run> Link: https://patchwork.freedesktop.org/patch/msgid/20200406221253.1307209-4-lyud… diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index e7a5bd3e6015..8942ab98ab64 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -27,6 +27,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/seq_file.h> +#include <linux/iopoll.h> #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS) #include <linux/stacktrace.h> @@ -4438,43 +4439,53 @@ static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr, return ret; } +static int do_get_act_status(struct drm_dp_aux *aux) +{ + int ret; + u8 status; + + ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status); + if (ret < 0) + return ret; + + return status; +} /** * drm_dp_check_act_status() - Polls for ACT handled status. * @mgr: manager to use * * Tries waiting for the MST hub to finish updating it's payload table by - * polling for the ACT handled bit. + * polling for the ACT handled bit for up to 3 seconds (yes-some hubs really + * take that long). * * Returns: * 0 if the ACT was handled in time, negative error code on failure. */ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr) { - int count = 0, ret; - u8 status; - - do { - ret = drm_dp_dpcd_readb(mgr->aux, - DP_PAYLOAD_TABLE_UPDATE_STATUS, - &status); - if (ret < 0) { - DRM_DEBUG_KMS("failed to read payload table status %d\n", - ret); - return ret; - } - - if (status & DP_PAYLOAD_ACT_HANDLED) - break; - count++; - udelay(100); - } while (count < 30); - - if (!(status & DP_PAYLOAD_ACT_HANDLED)) { - DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", - status, count); + /* + * There doesn't seem to be any recommended retry count or timeout in + * the MST specification. Since some hubs have been observed to take + * over 1 second to update their payload allocations under certain + * conditions, we use a rather large timeout value. + */ + const int timeout_ms = 3000; + int ret, status; + + ret = readx_poll_timeout(do_get_act_status, mgr->aux, status, + status & DP_PAYLOAD_ACT_HANDLED || status < 0, + 200, timeout_ms * USEC_PER_MSEC); + if (ret < 0 && status >= 0) { + DRM_DEBUG_KMS("Failed to get ACT after %dms, last status: %02x\n", + timeout_ms, status); return -EINVAL; + } else if (status < 0) { + DRM_DEBUG_KMS("Failed to read payload table status: %d\n", + status); + return status; } + return 0; } EXPORT_SYMBOL(drm_dp_check_act_status);

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Linux-stable-mirror June 2020