drm/msm/sde: remove redundant CRTC event caching

Currently both sde_crtc_atomic_begin() and
sde_crtc_atomic_flush() add the CRTC state event
to the cached sde_crtc->event.

This has a potential NULL ptr issue in the
case of vblank event firing in between sde_crtc_atomic_begin() and
sde_crtc_atomic_flush() because the upstream DRM vblank API
send_vblank_event() doesn't consider the case when the VBLANK
interrupt could have already freed any pending vblank events.

Remove the caching from sde_crtc_atomic_begin() to avoid this
condition.

Also make sure that a page_flip event was indeed submitted before
signaling the complete_flip() by setting a PENDING_FLIP flag right
after HW flush.

Change-Id: Ib201d2851e57bf22ec1f00814fc2e4dd2f35bfa1
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Yunyun Cao <yunyunc@codeaurora.org>

drivers/gpu/drm/msm/sde/sde_crtc.c

@@ -51,6 +51,9 @@
 #define LEFT_MIXER 0
 #define RIGHT_MIXER 1
 
+/* indicates pending page flip events */
+#define PENDING_FLIP   0x2
+
 static inline struct sde_kms *_sde_crtc_get_kms(struct drm_crtc *crtc)
 {
 	struct msm_drm_private *priv = crtc->dev->dev_private;
@@ -399,13 +402,18 @@ static void sde_crtc_vblank_cb(void *data)
 {
 	struct drm_crtc *crtc = (struct drm_crtc *)data;
 	struct sde_crtc *sde_crtc = to_sde_crtc(crtc);
+	unsigned pending;
 
+	pending = atomic_xchg(&sde_crtc->pending, 0);
 	/* keep statistics on vblank callback - with auto reset via debugfs */
 	if (ktime_equal(sde_crtc->vblank_cb_time, ktime_set(0, 0)))
 		sde_crtc->vblank_cb_time = ktime_get();
 	else
 		sde_crtc->vblank_cb_count++;
-	_sde_crtc_complete_flip(crtc, NULL);
+
+	if (pending & PENDING_FLIP)
+		_sde_crtc_complete_flip(crtc, NULL);
+
 	drm_crtc_handle_vblank(crtc);
 	DRM_DEBUG_VBL("crtc%d\n", crtc->base.id);
 	SDE_EVT32_IRQ(DRMID(crtc));
@@ -519,6 +527,28 @@ static void sde_crtc_frame_event_cb(void *data, u32 event)
 	queue_kthread_work(&priv->disp_thread[pipe_id].worker, &fevent->work);
 }
 
+/**
+ *  sde_crtc_request_flip_cb - callback to request page_flip events
+ * Once the HW flush is complete , userspace must be notified of
+ * PAGE_FLIP completed event in the next vblank event.
+ * Using this callback, a hint is set to signal any callers waiting
+ * for a PAGE_FLIP complete event.
+ * This is called within the enc_spinlock.
+ * @data: Pointer to cb private data
+ */
+static void sde_crtc_request_flip_cb(void *data)
+{
+	struct drm_crtc *crtc = (struct drm_crtc *)data;
+	struct sde_crtc *sde_crtc;
+
+	if (!crtc) {
+		SDE_ERROR("invalid parameters\n");
+		return;
+	}
+	sde_crtc = to_sde_crtc(crtc);
+	atomic_or(PENDING_FLIP, &sde_crtc->pending);
+}
+
 void sde_crtc_complete_commit(struct drm_crtc *crtc,
 		struct drm_crtc_state *old_state)
 {
@@ -679,7 +709,6 @@ static void sde_crtc_atomic_begin(struct drm_crtc *crtc,
 {
 	struct sde_crtc *sde_crtc;
 	struct drm_device *dev;
-	unsigned long flags;
 	u32 i;
 
 	if (!crtc) {
@@ -701,14 +730,6 @@ static void sde_crtc_atomic_begin(struct drm_crtc *crtc,
 	if (!sde_crtc->num_mixers)
 		_sde_crtc_setup_mixers(crtc);
 
-	if (sde_crtc->event) {
-		WARN_ON(sde_crtc->event);
-	} else {
-		spin_lock_irqsave(&dev->event_lock, flags);
-		sde_crtc->event = crtc->state->event;
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-	}
-
 	/* Reset flush mask from previous commit */
 	for (i = 0; i < ARRAY_SIZE(sde_crtc->mixers); i++) {
 		struct sde_hw_ctl *ctl = sde_crtc->mixers[i].hw_ctl;
@@ -763,7 +784,8 @@ static void sde_crtc_atomic_flush(struct drm_crtc *crtc,
 	dev = crtc->dev;
 
 	if (sde_crtc->event) {
-		SDE_DEBUG("already received sde_crtc->event\n");
+		SDE_ERROR("%s already received sde_crtc->event\n",
+				  sde_crtc->name);
 	} else {
 		spin_lock_irqsave(&dev->event_lock, flags);
 		sde_crtc->event = crtc->state->event;
@@ -999,6 +1021,7 @@ static void sde_crtc_disable(struct drm_crtc *crtc)
 		if (encoder->crtc != crtc)
 			continue;
 		sde_encoder_register_frame_event_callback(encoder, NULL, NULL);
+		sde_encoder_register_request_flip_callback(encoder, NULL, NULL);
 	}
 
 	memset(sde_crtc->mixers, 0, sizeof(sde_crtc->mixers));
@@ -1039,6 +1062,8 @@ static void sde_crtc_enable(struct drm_crtc *crtc)
 			continue;
 		sde_encoder_register_frame_event_callback(encoder,
 				sde_crtc_frame_event_cb, (void *)crtc);
+		sde_encoder_register_request_flip_callback(encoder,
+				sde_crtc_request_flip_cb, (void *)crtc);
 	}
 
 	for (i = 0; i < sde_crtc->num_mixers; i++) {

drivers/gpu/drm/msm/sde/sde_crtc.h

@@ -89,6 +89,7 @@ struct sde_crtc_frame_event {
  * @frame_pending : Whether or not an update is pending
  * @frame_events  : static allocation of in-flight frame events
  * @frame_event_list : available frame event list
+ * @pending       : Whether any page-flip events are pending signal
  * @spin_lock     : spin lock for frame event, transaction status, etc...
  */
 struct sde_crtc {
@@ -109,7 +110,7 @@ struct sde_crtc {
 
 	/* output fence support */
 	struct sde_fence output_fence;
-
+	atomic_t pending;
 	struct sde_hw_stage_cfg stage_cfg;
 	struct dentry *debugfs_root;
 

drivers/gpu/drm/msm/sde/sde_encoder.c

@@ -83,6 +83,8 @@
  *				Bit0 = phys_encs[0] etc.
  * @crtc_frame_event_cb:	callback handler for frame event
  * @crtc_frame_event_cb_data:	callback handler private data
+ * @crtc_request_flip_cb:	callback handler for requesting page-flip event
+ * @crtc_request_flip_cb_data:	callback handler private data
  * @crtc_frame_event:		callback event
  * @frame_done_timeout:		frame done timeout in Hz
  * @frame_done_timer:		watchdog timer for frame done event
@@ -107,8 +109,9 @@ struct sde_encoder_virt {
 	DECLARE_BITMAP(frame_busy_mask, MAX_PHYS_ENCODERS_PER_VIRTUAL);
 	void (*crtc_frame_event_cb)(void *, u32 event);
 	void *crtc_frame_event_cb_data;
+	void (*crtc_request_flip_cb)(void *);
+	void *crtc_request_flip_cb_data;
 	u32 crtc_frame_event;
-
 	atomic_t frame_done_timeout;
 	struct timer_list frame_done_timer;
 };
@@ -584,6 +587,24 @@ void sde_encoder_register_frame_event_callback(struct drm_encoder *drm_enc,
 	spin_unlock_irqrestore(&sde_enc->enc_spinlock, lock_flags);
 }
 
+void sde_encoder_register_request_flip_callback(struct drm_encoder *drm_enc,
+		void (*request_flip_cb)(void *),
+		void *request_flip_cb_data)
+{
+	struct sde_encoder_virt *sde_enc = to_sde_encoder_virt(drm_enc);
+	unsigned long lock_flags;
+
+	if (!drm_enc) {
+		SDE_ERROR("invalid encoder\n");
+		return;
+	}
+
+	spin_lock_irqsave(&sde_enc->enc_spinlock, lock_flags);
+	sde_enc->crtc_request_flip_cb = request_flip_cb;
+	sde_enc->crtc_request_flip_cb_data = request_flip_cb_data;
+	spin_unlock_irqrestore(&sde_enc->enc_spinlock, lock_flags);
+}
+
 static void sde_encoder_frame_done_callback(
 		struct drm_encoder *drm_enc,
 		struct sde_encoder_phys *ready_phys, u32 event)
@@ -759,6 +780,11 @@ static void _sde_encoder_kickoff_phys(struct sde_encoder_virt *sde_enc)
 				pending_flush);
 	}
 
+	/* HW flush has happened, request a flip complete event now */
+	if (sde_enc->crtc_request_flip_cb)
+		sde_enc->crtc_request_flip_cb(
+		sde_enc->crtc_request_flip_cb_data);
+
 	_sde_encoder_trigger_start(sde_enc->cur_master);
 
 	spin_unlock_irqrestore(&sde_enc->enc_spinlock, lock_flags);

drivers/gpu/drm/msm/sde/sde_encoder.h

@@ -71,6 +71,17 @@ void sde_encoder_register_vblank_callback(struct drm_encoder *encoder,
 void sde_encoder_register_frame_event_callback(struct drm_encoder *encoder,
 		void (*cb)(void *, u32), void *data);
 
+/**
+ * sde_encoder_register_request_flip_callback - provide callback to encoder that
+ * will be called after HW flush is complete to request
+ * a page flip event from CRTC.
+ * @encoder:	encoder pointer
+ * @cb:		callback pointer, provide NULL to deregister
+ * @data:	user data provided to callback
+ */
+void sde_encoder_register_request_flip_callback(struct drm_encoder *encoder,
+		void (*cb)(void *), void *data);
+
 /**
  * sde_encoder_prepare_for_kickoff - schedule double buffer flip of the ctl
  *	path (i.e. ctl flush and start) at next appropriate time.