drm/amd/display: Add NULL checks for vblank workqueue

[Why]
If we're running a headless config with 0 links then the vblank
workqueue will be NULL - causing a NULL pointer exception during
any commit.

[How]
Guard access to the workqueue if it's NULL and don't queue or flush
work if it is.

Reported-by: Mike Lothian <mike@fireburn.co.uk>
BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1700
Fixes: 58aa1c50e5a231 ("drm/amd/display: Use vblank control events for PSR enable/disable")
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index d55e61d..14ba5ee 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6024,21 +6024,23 @@ static inline int dm_set_vblank(struct drm_crtc *crtc, bool enable)
                return 0;
 
 #if defined(CONFIG_DRM_AMD_DC_DCN)
-       work = kzalloc(sizeof(*work), GFP_ATOMIC);
-       if (!work)
-               return -ENOMEM;
+       if (dm->vblank_control_workqueue) {
+               work = kzalloc(sizeof(*work), GFP_ATOMIC);
+               if (!work)
+                       return -ENOMEM;
 
-       INIT_WORK(&work->work, vblank_control_worker);
-       work->dm = dm;
-       work->acrtc = acrtc;
-       work->enable = enable;
+               INIT_WORK(&work->work, vblank_control_worker);
+               work->dm = dm;
+               work->acrtc = acrtc;
+               work->enable = enable;
 
-       if (acrtc_state->stream) {
-               dc_stream_retain(acrtc_state->stream);
-               work->stream = acrtc_state->stream;
-       }
+               if (acrtc_state->stream) {
+                       dc_stream_retain(acrtc_state->stream);
+                       work->stream = acrtc_state->stream;
+               }
 
-       queue_work(dm->vblank_control_workqueue, &work->work);
+               queue_work(dm->vblank_control_workqueue, &work->work);
+       }
 #endif
 
        return 0;
@@ -8648,7 +8650,8 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
                 * If PSR or idle optimizations are enabled then flush out
                 * any pending work before hardware programming.
                 */
-               flush_workqueue(dm->vblank_control_workqueue);
+               if (dm->vblank_control_workqueue)
+                       flush_workqueue(dm->vblank_control_workqueue);
 #endif
 
                bundle->stream_update.stream = acrtc_state->stream;
@@ -8983,7 +8986,8 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
                /* if there mode set or reset, disable eDP PSR */
                if (mode_set_reset_required) {
 #if defined(CONFIG_DRM_AMD_DC_DCN)
-                       flush_workqueue(dm->vblank_control_workqueue);
+                       if (dm->vblank_control_workqueue)
+                               flush_workqueue(dm->vblank_control_workqueue);
 #endif
                        amdgpu_dm_psr_disable_all(dm);
                }