The patch below does not apply to the 5.15-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:

d60b82aa4d67 ("drm/amdgpu/dm/dp_mst: Don't grab mst_mgr->lock when computing DSC state") 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 d60b82aa4d67b2e6cf0364947a008bb7255ca4da Mon Sep 17 00:00:00 2001 From: Lyude Paul lyude@redhat.com Date: Mon, 14 Nov 2022 17:17:55 -0500 Subject: [PATCH] drm/amdgpu/dm/dp_mst: Don't grab mst_mgr->lock when computing DSC state

Now that we've fixed the issue with using the incorrect topology manager, we're actually grabbing the topology manager's lock - and consequently deadlocking. Luckily for us though, there's actually nothing in AMD's DSC state computation code that really should need this lock. The one exception is the mutex_lock() in dm_dp_mst_is_port_support_mode(), however we grab no locks beneath &mgr->lock there so that should be fine to leave be.

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 5196c9a0e432..59648f5ffb59 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 @@ -1148,10 +1148,8 @@ int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, continue;

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); - mutex_unlock(&mst_mgr->lock); if (ret != 0) return ret;

@@ -1208,10 +1206,8 @@ static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state, continue;

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); - mutex_unlock(&mst_mgr->lock); if (ret != 0) return ret;