[PATCH v3 2/2] drm/msm/mdp5: Return error code in mdp5_mixer_release when deadlock is detected

[Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
---
 drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c  | 10 ++++++++--
 drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c | 15 +++++++++++----
 drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h |  4 ++--
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
index b966cd69f99d..fe2922c8d21b 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
+++ b/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;
 		}
diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c
index 954db683ae44..2536def2a000 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.c
+++ b/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)
diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h b/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h
index 43c9ba43ce18..545ee223b9d7 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_mixer.h
+++ b/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__ */
-- 
2.35.1