drm/msm/mdp5: Return error code in mdp5_mixer_release when deadlock is detected

There is a possibility for mdp5_get_global_state to return
-EDEADLK when acquiring the modeset lock, but currently global_state in
mdp5_mixer_release doesn't check for if an error is returned.

To avoid a NULL dereference error, let's have mdp5_mixer_release
check if an error is returned and propagate that error.
Reported-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Fixes: 7907a0d7 ("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/485181/
Link: https://lore.kernel.org/r/20220505214051.155-2-quic_jesszhan@quicinc.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c

@@ -612,9 +612,15 @@ static int mdp5_crtc_setup_pipeline(struct drm_crtc *crtc,
 		if (ret)
 			return ret;
 
-		mdp5_mixer_release(new_crtc_state->state, old_mixer);
+		ret = mdp5_mixer_release(new_crtc_state->state, old_mixer);
+		if (ret)
+			return ret;
+
 		if (old_r_mixer) {
-			mdp5_mixer_release(new_crtc_state->state, old_r_mixer);
+			ret = mdp5_mixer_release(new_crtc_state->state, old_r_mixer);
+			if (ret)
+				return ret;
+
 			if (!need_right_mixer)
 				pipeline->r_mixer = NULL;
 		}

drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c

@@ -116,21 +116,28 @@ int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
 	return 0;
 }
 
-void mdp5_mixer_release(struct drm_atomic_state *s, struct mdp5_hw_mixer *mixer)
+int mdp5_mixer_release(struct drm_atomic_state *s, struct mdp5_hw_mixer *mixer)
 {
 	struct mdp5_global_state *global_state = mdp5_get_global_state(s);
-	struct mdp5_hw_mixer_state *new_state = &global_state->hwmixer;
+	struct mdp5_hw_mixer_state *new_state;
 
 	if (!mixer)
-		return;
+		return 0;
+
+	if (IS_ERR(global_state))
+		return PTR_ERR(global_state);
+
+	new_state = &global_state->hwmixer;
 
 	if (WARN_ON(!new_state->hwmixer_to_crtc[mixer->idx]))
-		return;
+		return -EINVAL;
 
 	DBG("%s: release from crtc %s", mixer->name,
 	    new_state->hwmixer_to_crtc[mixer->idx]->name);
 
 	new_state->hwmixer_to_crtc[mixer->idx] = NULL;
+
+	return 0;
 }
 
 void mdp5_mixer_destroy(struct mdp5_hw_mixer *mixer)

drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h

@@ -30,7 +30,7 @@ void mdp5_mixer_destroy(struct mdp5_hw_mixer *lm);
 int mdp5_mixer_assign(struct drm_atomic_state *s, struct drm_crtc *crtc,
 		      uint32_t caps, struct mdp5_hw_mixer **mixer,
 		      struct mdp5_hw_mixer **r_mixer);
-void mdp5_mixer_release(struct drm_atomic_state *s,
-			struct mdp5_hw_mixer *mixer);
+int mdp5_mixer_release(struct drm_atomic_state *s,
+		       struct mdp5_hw_mixer *mixer);
 
 #endif /* __MDP5_LM_H__ */