Re: [PATCHv2 41/45] drm: omapdrm: remove omap_crtc_wait_page_flip

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 06/06/15 07:09, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thursday 04 June 2015 12:02:58 Tomi Valkeinen wrote:
>> omap_crtc_disable() waits for pending page flips to finish. However,
>> omap_crtc_disable() is always called via omap_atomic_complete() and we
>> never have page flips going on at that time.
> 
> Why is that ? Because our omap_atomic_complete() implementation waits for 
> vblanks before allowing the next atomic commit to run, and that our vblank IRQ 
> handler completes all pending page flips ? If so, I believe we have a few 
> corner cases that won't work properly.

Yes, I think what omap_atomic_complete() is supposed to do is to wait until
everything is done for the affected crtcs. But you are right, it wasn't quite
correct.

> For instance, if the user performs a full mode set on a CRTC without change 
> the framebuffer, an event can be queued but 
> drm_atomic_helper_wait_for_vblanks() won't wait for vblank on that CRTC as 
> framebuffer_changed() will return false. If the next commit then disables the 
> CRTC the event might not have completed yet.

I reworked the event/flip_wait code, removing this patch and 42 and 43. I didn't
have time to clean it up properly, but I'm probably not able to work on it for
the following days, so I'll post it now. Quick testing went fine.

I also pushed it to omapdrm-atomic-v2 branch.

From 8d6429616783c335d20bf8ebaf8cc4dc447d0385 Mon Sep 17 00:00:00 2001
From: Tomi Valkeinen <tomi.valkeinen@ti.com>
Date: Fri, 29 May 2015 16:01:18 +0300
Subject: [PATCH] drm: omapdrm: new vblank and event handling

Rework the crtc event/flip_wait system as follows:

- If we enable a crtc (full modeset), we set omap_crtc->pending and
  register vblank irq.

- If we need to set GO bit (page flip), we do the same but also set the
  GO bit.

- On vblank we unregister the irq, clear the 'pending' flag, send vblank
  event to userspace if crtc->state->event != NULL, and wake up
  'pending_wait' wq.

- In omap_atomic_complete() we wait for the 'pending' flag to get reset
  for all enabled crtcs  using 'pending_wait wq.

The above ensures that we send the events to userspace in vblank, and
that after the wait in omap_atomic_complete() everything for the
affected crtcs has been completed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c b/drivers/gpu/drm/omapdrm/omap_crtc.c
index 8d2bf8565ddd..9b067d10e8d2 100644
--- a/drivers/gpu/drm/omapdrm/omap_crtc.c
+++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
@@ -17,8 +17,6 @@
  * this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <linux/completion.h>
-
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
@@ -49,13 +47,10 @@ struct omap_crtc {
 	struct omap_drm_irq vblank_irq;
 	struct omap_drm_irq error_irq;
 
-	/* pending event */
-	struct drm_pending_vblank_event *event;
-	wait_queue_head_t flip_wait;
-
-	struct completion completion;
-
 	bool ignore_digit_sync_lost;
+
+	bool pending;
+	wait_queue_head_t pending_wait;
 };
 
 /* -----------------------------------------------------------------------------
@@ -81,6 +76,15 @@ enum omap_channel omap_crtc_channel(struct drm_crtc *crtc)
 	return omap_crtc->channel;
 }
 
+int omap_crtc_wait_pending(struct drm_crtc *crtc)
+{
+	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
+
+	return wait_event_timeout(omap_crtc->pending_wait,
+				  !omap_crtc->pending,
+				  msecs_to_jiffies(50));
+}
+
 /* -----------------------------------------------------------------------------
  * DSS Manager Functions
  */
@@ -253,77 +257,45 @@ static const struct dss_mgr_ops mgr_ops = {
  * Setup, Flush and Page Flip
  */
 
-static void omap_crtc_complete_page_flip(struct drm_crtc *crtc)
+static void omap_crtc_error_irq(struct omap_drm_irq *irq, uint32_t irqstatus)
 {
-	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
-	struct drm_pending_vblank_event *event;
-	struct drm_device *dev = crtc->dev;
-	unsigned long flags;
-
-	spin_lock_irqsave(&dev->event_lock, flags);
-
-	event = omap_crtc->event;
-	omap_crtc->event = NULL;
-
-	if (event) {
-		list_del(&event->base.link);
-
-		/*
-		 * Queue the event for delivery if it's still linked to a file
-		 * handle, otherwise just destroy it.
-		 */
-		if (event->base.file_priv)
-			drm_crtc_send_vblank_event(crtc, event);
-		else
-			event->base.destroy(&event->base);
+	struct omap_crtc *omap_crtc =
+			container_of(irq, struct omap_crtc, error_irq);
 
-		wake_up(&omap_crtc->flip_wait);
-		drm_crtc_vblank_put(crtc);
+	if (omap_crtc->ignore_digit_sync_lost) {
+		irqstatus &= ~DISPC_IRQ_SYNC_LOST_DIGIT;
+		if (!irqstatus)
+			return;
 	}
 
-	spin_unlock_irqrestore(&dev->event_lock, flags);
+	DRM_ERROR_RATELIMITED("%s: errors: %08x\n", omap_crtc->name, irqstatus);
 }
 
-static bool omap_crtc_page_flip_pending(struct drm_crtc *crtc)
+static void omap_crtc_complete_page_flip(struct drm_crtc *crtc)
 {
-	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
+	struct drm_pending_vblank_event *event;
 	struct drm_device *dev = crtc->dev;
 	unsigned long flags;
-	bool pending;
 
-	spin_lock_irqsave(&dev->event_lock, flags);
-	pending = omap_crtc->event != NULL;
-	spin_unlock_irqrestore(&dev->event_lock, flags);
+	event = crtc->state->event;
 
-	return pending;
-}
-
-static void omap_crtc_wait_page_flip(struct drm_crtc *crtc)
-{
-	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
-
-	if (wait_event_timeout(omap_crtc->flip_wait,
-			       !omap_crtc_page_flip_pending(crtc),
-			       msecs_to_jiffies(50)))
+	if (!event)
 		return;
 
-	dev_warn(crtc->dev->dev, "page flip timeout!\n");
-
-	omap_crtc_complete_page_flip(crtc);
-}
+	spin_lock_irqsave(&dev->event_lock, flags);
 
-static void omap_crtc_error_irq(struct omap_drm_irq *irq, uint32_t irqstatus)
-{
-	struct omap_crtc *omap_crtc =
-			container_of(irq, struct omap_crtc, error_irq);
+	list_del(&event->base.link);
 
-	if (omap_crtc->ignore_digit_sync_lost) {
-		irqstatus &= ~DISPC_IRQ_SYNC_LOST_DIGIT;
-		if (!irqstatus)
-			return;
-	}
+	/*
+	 * Queue the event for delivery if it's still linked to a file
+	 * handle, otherwise just destroy it.
+	 */
+	if (event->base.file_priv)
+		drm_crtc_send_vblank_event(crtc, event);
+	else
+		event->base.destroy(&event->base);
 
-	DRM_ERROR_RATELIMITED("%s: errors: %08x\n", omap_crtc->name, irqstatus);
+	spin_unlock_irqrestore(&dev->event_lock, flags);
 }
 
 static void omap_crtc_vblank_irq(struct omap_drm_irq *irq, uint32_t irqstatus)
@@ -336,12 +308,19 @@ static void omap_crtc_vblank_irq(struct omap_drm_irq *irq, uint32_t irqstatus)
 		return;
 
 	DBG("%s: apply done", omap_crtc->name);
+
 	__omap_irq_unregister(dev, &omap_crtc->vblank_irq);
 
-	/* wakeup userspace */
+	mb();
+	WARN_ON(!omap_crtc->pending);
+	omap_crtc->pending = false;
+	mb();
+
+	/* wake up userspace */
 	omap_crtc_complete_page_flip(&omap_crtc->base);
 
-	complete(&omap_crtc->completion);
+	/* wake up omap_atomic_complete */
+	wake_up(&omap_crtc->pending_wait);
 }
 
 /* -----------------------------------------------------------------------------
@@ -375,6 +354,13 @@ static void omap_crtc_enable(struct drm_crtc *crtc)
 
 	DBG("%s", omap_crtc->name);
 
+	WARN_ON(omap_crtc->pending);
+
+	omap_crtc->pending = true;
+	mb();
+
+	omap_irq_register(crtc->dev, &omap_crtc->vblank_irq);
+
 	drm_crtc_vblank_on(crtc);
 }
 
@@ -384,7 +370,6 @@ static void omap_crtc_disable(struct drm_crtc *crtc)
 
 	DBG("%s", omap_crtc->name);
 
-	omap_crtc_wait_page_flip(crtc);
 	drm_crtc_vblank_off(crtc);
 }
 
@@ -405,19 +390,7 @@ static void omap_crtc_mode_set_nofb(struct drm_crtc *crtc)
 
 static void omap_crtc_atomic_begin(struct drm_crtc *crtc)
 {
-	struct drm_pending_vblank_event *event = crtc->state->event;
-	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
-	struct drm_device *dev = crtc->dev;
-	unsigned long flags;
-
-	if (event) {
-		WARN_ON(omap_crtc->event);
-		WARN_ON(drm_crtc_vblank_get(crtc) != 0);
 
-		spin_lock_irqsave(&dev->event_lock, flags);
-		omap_crtc->event = event;
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-	}
 }
 
 static void omap_crtc_atomic_flush(struct drm_crtc *crtc)
@@ -425,16 +398,16 @@ static void omap_crtc_atomic_flush(struct drm_crtc *crtc)
 	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
 
 	WARN_ON(omap_crtc->vblank_irq.registered);
+	WARN_ON(omap_crtc->pending);
 
 	if (dispc_mgr_is_enabled(omap_crtc->channel)) {
 		DBG("%s: GO", omap_crtc->name);
 
+		omap_crtc->pending = true;
+		mb();
+
 		dispc_mgr_go(omap_crtc->channel);
 		omap_irq_register(crtc->dev, &omap_crtc->vblank_irq);
-
-		WARN_ON(!wait_for_completion_timeout(&omap_crtc->completion,
-						     msecs_to_jiffies(100)));
-		reinit_completion(&omap_crtc->completion);
 	}
 
 	crtc->invert_dimensions = !!(crtc->primary->state->rotation &
@@ -534,8 +507,7 @@ struct drm_crtc *omap_crtc_init(struct drm_device *dev,
 
 	crtc = &omap_crtc->base;
 
-	init_waitqueue_head(&omap_crtc->flip_wait);
-	init_completion(&omap_crtc->completion);
+	init_waitqueue_head(&omap_crtc->pending_wait);
 
 	omap_crtc->channel = channel;
 	omap_crtc->name = channel_names[channel];
diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
index 50f555530e55..e8f4001d9d31 100644
--- a/drivers/gpu/drm/omapdrm/omap_drv.c
+++ b/drivers/gpu/drm/omapdrm/omap_drv.c
@@ -66,6 +66,25 @@ struct omap_atomic_state_commit {
 	u32 crtcs;
 };
 
+static void omap_atomic_wait_for_gos(struct drm_device *dev,
+					 struct drm_atomic_state *old_state)
+{
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *old_crtc_state;
+	int i, ret;
+
+	for_each_crtc_in_state(old_state, crtc, old_crtc_state, i) {
+		if (!crtc->state->enable)
+			continue;
+
+		ret = omap_crtc_wait_pending(crtc);
+
+		if (!ret)
+			dev_warn(dev->dev,
+				 "atomic flush timeout (pipe %u)!\n", i);
+	}
+}
+
 static void omap_atomic_complete(struct omap_atomic_state_commit *commit)
 {
 	struct drm_device *dev = commit->dev;
@@ -79,7 +98,7 @@ static void omap_atomic_complete(struct omap_atomic_state_commit *commit)
 	drm_atomic_helper_commit_planes(dev, old_state);
 	drm_atomic_helper_commit_modeset_enables(dev, old_state);
 
-	drm_atomic_helper_wait_for_vblanks(dev, old_state);
+	omap_atomic_wait_for_gos(dev, old_state);
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
 
diff --git a/drivers/gpu/drm/omapdrm/omap_drv.h b/drivers/gpu/drm/omapdrm/omap_drv.h
index 0b7a055bf007..ae2df41f216f 100644
--- a/drivers/gpu/drm/omapdrm/omap_drv.h
+++ b/drivers/gpu/drm/omapdrm/omap_drv.h
@@ -147,6 +147,7 @@ void omap_crtc_pre_init(void);
 void omap_crtc_pre_uninit(void);
 struct drm_crtc *omap_crtc_init(struct drm_device *dev,
 		struct drm_plane *plane, enum omap_channel channel, int id);
+int omap_crtc_wait_pending(struct drm_crtc *crtc);
 
 struct drm_plane *omap_plane_init(struct drm_device *dev,
 		int id, enum drm_plane_type type);


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