[PATCH v2] drm/amd/display: Fix artifacting on eDP panels when engaging freesync video mode

[Aurabindo Pillai]

[Why]
When freesync video mode is enabled, switching resolution from native
mode to one of the freesync video compatible modes can trigger continous
artifacts on some eDP panels when running under KDE. The articating can be seen in the
attached bug report.

[How]
Fix this by restricting updates that does not require full commit by using the
same checks for stream and scaling changes in the the enable pass of dm_update_crtc_state()
along with the check for compatible timings for freesync vide mode.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2162
Fixes: 541d54055b75 ("drm/amd/display: Fix hang when skipping modeset")
Signed-off-by: Aurabindo Pillai <aurabindo.pillai at amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 ++
 1 file changed, 2 insertions(+)

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 14b296e1d0f6..7f322b18eda6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -9285,6 +9285,8 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
 
 		/* Now check if we should set freesync video mode */
 		if (amdgpu_freesync_vid_mode && dm_new_crtc_state->stream &&
+		    dc_is_stream_unchanged(new_stream, dm_old_crtc_state->stream) &&
+		    dc_is_stream_scaling_unchanged(new_stream, dm_old_crtc_state->stream) &&
 		    is_timing_unchanged_for_freesync(new_crtc_state,
 						     old_crtc_state)) {
 			new_crtc_state->mode_changed = false;
-- 
2.40.1