[PATCH v2] drm/amd/display: Fix vblank refcount in vrr transition

[Yunxiang Li]

manage_dm_interrupts disable/enable vblank using drm_crtc_vblank_off/on
which causes drm_crtc_vblank_get in vrr_transition to fail, and later
when drm_crtc_vblank_put is called the refcount on vblank will be messed
up. Therefore move the call to after manage_dm_interrupts.

Unchecked calls to drm_crtc_vblank_get seems to be common in other
drivers as well so it may make sense to let get always succeed during
modset, see
https://lists.freedesktop.org/archives/dri-devel/2022-July/365589.html

Signed-off-by: Yunxiang Li <Yunxiang.Li at amd.com>
---
v2: check the return code for calls that might fail and warn on them

 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 34 ++++++++-----------
 1 file changed, 14 insertions(+), 20 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 92470a0e0262..9f3fdb92e7a4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7480,15 +7480,15 @@ static void amdgpu_dm_handle_vrr_transition(struct dm_crtc_state *old_state,
 		 * We also need vupdate irq for the actual core vblank handling
 		 * at end of vblank.
 		 */
-		dm_set_vupdate_irq(new_state->base.crtc, true);
-		drm_crtc_vblank_get(new_state->base.crtc);
+		WARN_ON(dm_set_vupdate_irq(new_state->base.crtc, true) != 0);
+		WARN_ON(drm_crtc_vblank_get(new_state->base.crtc) != 0);
 		DRM_DEBUG_DRIVER("%s: crtc=%u VRR off->on: Get vblank ref\n",
 				 __func__, new_state->base.crtc->base.id);
 	} else if (old_vrr_active && !new_vrr_active) {
 		/* Transition VRR active -> inactive:
 		 * Allow vblank irq disable again for fixed refresh rate.
 		 */
-		dm_set_vupdate_irq(new_state->base.crtc, false);
+		WARN_ON(dm_set_vupdate_irq(new_state->base.crtc, false) != 0);
 		drm_crtc_vblank_put(new_state->base.crtc);
 		DRM_DEBUG_DRIVER("%s: crtc=%u VRR on->off: Drop vblank ref\n",
 				 __func__, new_state->base.crtc->base.id);
@@ -8252,23 +8252,6 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		mutex_unlock(&dm->dc_lock);
 	}
 
-	/* Count number of newly disabled CRTCs for dropping PM refs later. */
-	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
-				      new_crtc_state, i) {
-		if (old_crtc_state->active && !new_crtc_state->active)
-			crtc_disable_count++;
-
-		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
-		dm_old_crtc_state = to_dm_crtc_state(old_crtc_state);
-
-		/* For freesync config update on crtc state and params for irq */
-		update_stream_irq_parameters(dm, dm_new_crtc_state);
-
-		/* Handle vrr on->off / off->on transitions */
-		amdgpu_dm_handle_vrr_transition(dm_old_crtc_state,
-						dm_new_crtc_state);
-	}
-
 	/**
 	 * Enable interrupts for CRTCs that are newly enabled or went through
 	 * a modeset. It was intentionally deferred until after the front end
@@ -8287,7 +8270,15 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		cur_crc_src = acrtc->dm_irq_params.crc_src;
 		spin_unlock_irqrestore(&adev_to_drm(adev)->event_lock, flags);
 #endif
+		/* Count number of newly disabled CRTCs for dropping PM refs later. */
+		if (old_crtc_state->active && !new_crtc_state->active)
+			crtc_disable_count++;
+
 		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
+		dm_old_crtc_state = to_dm_crtc_state(old_crtc_state);
+
+		/* For freesync config update on crtc state and params for irq */
+		update_stream_irq_parameters(dm, dm_new_crtc_state);
 
 		if (new_crtc_state->active &&
 		    (!old_crtc_state->active ||
@@ -8324,6 +8315,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 					DRM_DEBUG_DRIVER("Failed to configure crc source");
 #endif
 		}
+
+		/* Handle vrr on->off / off->on transitions */
+		amdgpu_dm_handle_vrr_transition(dm_old_crtc_state, dm_new_crtc_state);
 	}
 
 	for_each_new_crtc_in_state(state, crtc, new_crtc_state, j)
-- 
2.37.1