The patch below does not apply to the 5.5-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@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 64e62bdf04ab8529f45ed0a85122c703035dec3a Mon Sep 17 00:00:00 2001

From: Wayne Lin Wayne.Lin@amd.com Date: Thu, 5 Dec 2019 17:00:43 +0800 Subject: [PATCH] drm/dp_mst: Remove VCPI while disabling topology mgr

[Why]

This patch is trying to address the issue observed when hotplug DP daisy chain monitors.

e.g. src-mstb-mstb-sst -> src (unplug) mstb-mstb-sst -> src-mstb-mstb-sst (plug in again)

Once unplug a DP MST capable device, driver will call drm_dp_mst_topology_mgr_set_mst() to disable MST. In this function, it cleans data of topology manager while disabling mst_state. However, it doesn't clean up the proposed_vcpis of topology manager. If proposed_vcpi is not reset, once plug in MST daisy chain monitors later, code will fail at checking port validation while trying to allocate payloads.

When MST capable device is plugged in again and try to allocate payloads by calling drm_dp_update_payload_part1(), this function will iterate over all proposed virtual channels to see if any proposed VCPI's num_slots is greater than 0. If any proposed VCPI's num_slots is greater than 0 and the port which the specific virtual channel directed to is not in the topology, code then fails at the port validation. Since there are stale VCPI allocations from the previous topology enablement in proposed_vcpi[], code will fail at port validation and reurn EINVAL.

[How]

Clean up the data of stale proposed_vcpi[] and reset mgr->proposed_vcpis to NULL while disabling mst in drm_dp_mst_topology_mgr_set_mst().

Changes since v1: *Add on more details in commit message to describe the issue which the patch is trying to fix

Signed-off-by: Wayne Lin Wayne.Lin@amd.com [added cc to stable] Signed-off-by: Lyude Paul lyude@redhat.com Link: https://patchwork.freedesktop.org/patch/msgid/20191205090043.7580-1-Wayne.Li... Cc: stable@vger.kernel.org # v3.17+

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 87fc44895d83..1770754bcd4a 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3054,6 +3054,7 @@ static int drm_dp_get_vc_payload_bw(u8 dp_link_bw, u8 dp_link_count) int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state) { int ret = 0; + int i = 0; struct drm_dp_mst_branch *mstb = NULL;

mutex_lock(&mgr->lock); @@ -3114,10 +3115,22 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms /* this can fail if the device is gone */ drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0); ret = 0; + mutex_lock(&mgr->payload_lock); memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload)); mgr->payload_mask = 0; set_bit(0, &mgr->payload_mask); + for (i = 0; i < mgr->max_payloads; i++) { + struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i]; + + if (vcpi) { + vcpi->vcpi = 0; + vcpi->num_slots = 0; + } + mgr->proposed_vcpis[i] = NULL; + } mgr->vcpi_mask = 0; + mutex_unlock(&mgr->payload_lock); + mgr->payload_id_table_cleared = false; }