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 4d07b0bc ("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/2171Signed-off-by: Lyude Paul <lyude@redhat.com> Fixes: 8c20a1ed ("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>
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