drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected

mdp5_get_global_state runs the risk of hitting a -EDEADLK when acquiring
the modeset lock, but currently mdp5_pipe_release doesn't check for if
an error is returned. Because of this, there is a possibility of
mdp5_pipe_release hitting a NULL dereference error.

To avoid this, let's have mdp5_pipe_release check if
mdp5_get_global_state returns an error and propogate that error.

Changes since v1:
- Separated declaration and initialization of *new_state to avoid
  compiler warning
- Fixed some spelling mistakes in commit message

Changes since v2:
- Return 0 in case where hwpipe is NULL as this is considered normal
  behavior
- Added 2nd patch in series to fix a similar NULL dereference issue in
  mdp5_mixer_release

Reported-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Fixes: 7907a0d77c ("drm/msm/mdp5: Use the new private_obj state")
Reviewed-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/485179/
Link: https://lore.kernel.org/r/20220505214051.155-1-quic_jesszhan@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c

@@ -119,18 +119,23 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
 	return 0;
 }
 
-void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
+int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
 {
 	struct msm_drm_private *priv = s->dev->dev_private;
 	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
 	struct mdp5_global_state *state = mdp5_get_global_state(s);
-	struct mdp5_hw_pipe_state *new_state = &state->hwpipe;
+	struct mdp5_hw_pipe_state *new_state;
 
 	if (!hwpipe)
-		return;
+		return 0;
+
+	if (IS_ERR(state))
+		return PTR_ERR(state);
+
+	new_state = &state->hwpipe;
 
 	if (WARN_ON(!new_state->hwpipe_to_plane[hwpipe->idx]))
-		return;
+		return -EINVAL;
 
 	DBG("%s: release from plane %s", hwpipe->name,
 		new_state->hwpipe_to_plane[hwpipe->idx]->name);
@@ -141,6 +146,8 @@ void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
 	}
 
 	new_state->hwpipe_to_plane[hwpipe->idx] = NULL;
+
+	return 0;
 }
 
 void mdp5_pipe_destroy(struct mdp5_hw_pipe *hwpipe)

drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h

@@ -37,7 +37,7 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
 		     uint32_t caps, uint32_t blkcfg,
 		     struct mdp5_hw_pipe **hwpipe,
 		     struct mdp5_hw_pipe **r_hwpipe);
-void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
+int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
 
 struct mdp5_hw_pipe *mdp5_pipe_init(enum mdp5_pipe pipe,
 		uint32_t reg_offset, uint32_t caps);

drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c

@@ -311,12 +311,24 @@ static int mdp5_plane_atomic_check_with_state(struct drm_crtc_state *crtc_state,
 				mdp5_state->r_hwpipe = NULL;
 
 
-			mdp5_pipe_release(state->state, old_hwpipe);
-			mdp5_pipe_release(state->state, old_right_hwpipe);
+			ret = mdp5_pipe_release(state->state, old_hwpipe);
+			if (ret)
+				return ret;
+
+			ret = mdp5_pipe_release(state->state, old_right_hwpipe);
+			if (ret)
+				return ret;
+
 		}
 	} else {
-		mdp5_pipe_release(state->state, mdp5_state->hwpipe);
-		mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
+		ret = mdp5_pipe_release(state->state, mdp5_state->hwpipe);
+		if (ret)
+			return ret;
+
+		ret = mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
+		if (ret)
+			return ret;
+
 		mdp5_state->hwpipe = mdp5_state->r_hwpipe = NULL;
 	}