drm/amd/display: Enable vblank interrupt during CRC capture

[Why]
In order to read CRC events when CRC capture is enabled the vblank
interrput handler needs to be running for the CRTC. The handler is
enabled while there is an active vblank reference.

When running IGT tests there will often be no active vblank reference
but the test expects to read a CRC value. This is valid usage (and
works on i915 since they have a CRC interrupt handler) so the reference
to the vblank should be grabbed while capture is active.

This issue was found running:

igt@kms_plane_multiple@atomic-pipe-b-tiling-none

The pipe-b is the only one in the initial commit and was not previously
active so no vblank reference is grabbed. The vblank interrupt is
not enabled and the test times out.

[How]
Keep a reference to the vblank as long as CRC capture is enabled.
If userspace never explicitly disables it then the reference is
also dropped when removing the CRTC from the context (stream = NULL).

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 13 insertions, 1 deletions

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 407f733a47ea..b0bdf5ceed0e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4917,10 +4917,22 @@ static int amdgpu_dm_atomic_commit(struct drm_device *dev,
 	 */
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		struct dm_crtc_state *dm_old_crtc_state = to_dm_crtc_state(old_crtc_state);
+		struct dm_crtc_state *dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
 		struct amdgpu_crtc *acrtc = to_amdgpu_crtc(crtc);
 
-		if (drm_atomic_crtc_needs_modeset(new_crtc_state) && dm_old_crtc_state->stream)
+		if (drm_atomic_crtc_needs_modeset(new_crtc_state)
+		    && dm_old_crtc_state->stream) {
+			/*
+			 * CRC capture was enabled but not disabled.
+			 * Release the vblank reference.
+			 */
+			if (dm_new_crtc_state->crc_enabled) {
+				drm_crtc_vblank_put(crtc);
+				dm_new_crtc_state->crc_enabled = false;
+			}
+
 			manage_dm_interrupts(adev, acrtc, false);
+		}
 	}
 	/*
 	 * Add check here for SoC's that support hardware cursor plane, to