The patch below does not apply to the 6.0-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.

Possible dependencies:

dfbc00410c48 ("drm/amdgpu/dm/mst: Use the correct topology mgr pointer in amdgpu_dm_connector") ba891436c2d2 ("drm/amdgpu/mst: Stop ignoring error codes and deadlocking") 876fcc4222e1 ("drm/amd/display: Validate DSC After Enable All New CRTCs") 47519d8224ba ("Merge tag 'amd-drm-next-6.1-2022-09-08' of https://gitlab.freedesktop.org/agd5f/linux into drm-next")

thanks,

greg k-h

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

From dfbc00410c48a9896d4a65600be7137202517780 Mon Sep 17 00:00:00 2001 From: Lyude Paul lyude@redhat.com Date: Mon, 14 Nov 2022 17:17:54 -0500 Subject: [PATCH] drm/amdgpu/dm/mst: Use the correct topology mgr pointer in amdgpu_dm_connector

This bug hurt me. Basically, it appears that we've been grabbing the entirely wrong mutex in the MST DSC computation code for amdgpu! While we've been grabbing:

amdgpu_dm_connector->mst_mgr

That's zero-initialized memory, because the only connectors we'll ever actually be doing DSC computations for are MST ports. Which have mst_mgr zero-initialized, and instead have the correct topology mgr pointer located at:

amdgpu_dm_connector->mst_port->mgr;

I'm a bit impressed that until now, this code has managed not to crash anyone's systems! It does seem to cause a warning in LOCKDEP though:

[ 66.637670] DEBUG_LOCKS_WARN_ON(lock->magic != lock)

This was causing the problems that appeared to have been introduced by:

commit 4d07b0bc4034 ("drm/display/dp_mst: Move all payload info into the atomic state")

This wasn't actually where they came from though. Presumably, before the only thing we were doing with the topology mgr pointer was attempting to grab mst_mgr->lock. Since the above commit however, we grab much more information from mst_mgr including the atomic MST state and respective modesetting locks.

This patch also implies that up until now, it's quite likely we could be susceptible to race conditions when going through the MST topology state for DSC computations since we technically will not have grabbed any lock when going through it.

So, let's fix this by adjusting all the respective code paths to look at the right pointer and skip things that aren't actual MST connectors from a topology.

Gitlab issue: https://gitlab.freedesktop.org/drm/amd/-/issues/2171

Signed-off-by: Lyude Paul lyude@redhat.com Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share") Cc: stable@vger.kernel.org # v5.6+ Reviewed-by: Wayne Lin Wayne.Lin@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c index bba2e8aaa2c2..5196c9a0e432 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c @@ -1117,6 +1117,7 @@ int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, struct dc_stream_state *stream; bool computed_streams[MAX_PIPES]; struct amdgpu_dm_connector *aconnector; + struct drm_dp_mst_topology_mgr *mst_mgr; int link_vars_start_index = 0; int ret = 0;

@@ -1131,7 +1132,7 @@ int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,

aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;

- if (!aconnector || !aconnector->dc_sink) + if (!aconnector || !aconnector->dc_sink || !aconnector->port) continue;

if (!aconnector->dc_sink->dsc_caps.dsc_dec_caps.is_dsc_supported) @@ -1146,16 +1147,13 @@ int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, if (!is_dsc_need_re_compute(state, dc_state, stream->link)) continue;

- mutex_lock(&aconnector->mst_mgr.lock); - - ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars, - &aconnector->mst_mgr, + mst_mgr = aconnector->port->mgr; + mutex_lock(&mst_mgr->lock); + ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars, mst_mgr, &link_vars_start_index); - if (ret != 0) { - mutex_unlock(&aconnector->mst_mgr.lock); + mutex_unlock(&mst_mgr->lock); + if (ret != 0) return ret; - } - mutex_unlock(&aconnector->mst_mgr.lock);

for (j = 0; j < dc_state->stream_count; j++) { if (dc_state->streams[j]->link == stream->link) @@ -1182,6 +1180,7 @@ static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, struct dc_stream_state *stream; bool computed_streams[MAX_PIPES]; struct amdgpu_dm_connector *aconnector; + struct drm_dp_mst_topology_mgr *mst_mgr; int link_vars_start_index = 0; int ret;

@@ -1196,7 +1195,7 @@ static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,

aconnector = (struct amdgpu_dm_connector *)stream->dm_stream_context;

- if (!aconnector || !aconnector->dc_sink) + if (!aconnector || !aconnector->dc_sink || !aconnector->port) continue;

if (!aconnector->dc_sink->dsc_caps.dsc_dec_caps.is_dsc_supported) @@ -1208,15 +1207,13 @@ static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, if (!is_dsc_need_re_compute(state, dc_state, stream->link)) continue;

- mutex_lock(&aconnector->mst_mgr.lock); - ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars, - &aconnector->mst_mgr, + mst_mgr = aconnector->port->mgr; + mutex_lock(&mst_mgr->lock); + ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars, mst_mgr, &link_vars_start_index); - if (ret != 0) { - mutex_unlock(&aconnector->mst_mgr.lock); + mutex_unlock(&mst_mgr->lock); + if (ret != 0) return ret; - } - mutex_unlock(&aconnector->mst_mgr.lock);

for (j = 0; j < dc_state->stream_count; j++) { if (dc_state->streams[j]->link == stream->link) @@ -1419,6 +1416,7 @@ enum dc_status dm_dp_mst_is_port_support_mode( unsigned int upper_link_bw_in_kbps = 0, down_link_bw_in_kbps = 0; unsigned int max_compressed_bw_in_kbps = 0; struct dc_dsc_bw_range bw_range = {0}; + struct drm_dp_mst_topology_mgr *mst_mgr;

/* * check if the mode could be supported if DSC pass-through is supported @@ -1427,7 +1425,8 @@ enum dc_status dm_dp_mst_is_port_support_mode( */ if (is_dsc_common_config_possible(stream, &bw_range) && aconnector->port->passthrough_aux) { - mutex_lock(&aconnector->mst_mgr.lock); + mst_mgr = aconnector->port->mgr; + mutex_lock(&mst_mgr->lock);

cur_link_settings = stream->link->verified_link_cap;

@@ -1440,7 +1439,7 @@ enum dc_status dm_dp_mst_is_port_support_mode( end_to_end_bw_in_kbps = min(upper_link_bw_in_kbps, down_link_bw_in_kbps);

- mutex_unlock(&aconnector->mst_mgr.lock); + mutex_unlock(&mst_mgr->lock);

/* * use the maximum dsc compression bandwidth as the required