Merge tag 'for-v4.6-rc/omap-fixes-a' of git://git.kernel.org/pub/scm/linux/kernel/git/pjw/omap-pending into omap-for-v4.6/fixes

ARM: OMAP2+: first hwmod fix for v4.6-rc

Fix a longstanding bug in the hwmod code that could cause
hardware SYSCONFIG register values to not match the kernel's
idea of what they should be, and that could result in lower
performance during IP block idle entry.

Basic build, boot, and PM test logs are available here:

http://www.pwsan.com/omap/testlogs/omap-hwmod-fixes-a-for-v4.6-rc/20160326231727/

1 files changed, 76 insertions, 15 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index d12a4efa651b..881c5a6c180c 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -224,6 +224,64 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
 		diff = (flags & DRM_CALLED_FROM_VBLIRQ) != 0;
 	}
 
+	/*
+	 * Within a drm_vblank_pre_modeset - drm_vblank_post_modeset
+	 * interval? If so then vblank irqs keep running and it will likely
+	 * happen that the hardware vblank counter is not trustworthy as it
+	 * might reset at some point in that interval and vblank timestamps
+	 * are not trustworthy either in that interval. Iow. this can result
+	 * in a bogus diff >> 1 which must be avoided as it would cause
+	 * random large forward jumps of the software vblank counter.
+	 */
+	if (diff > 1 && (vblank->inmodeset & 0x2)) {
+		DRM_DEBUG_VBL("clamping vblank bump to 1 on crtc %u: diffr=%u"
+			      " due to pre-modeset.\n", pipe, diff);
+		diff = 1;
+	}
+
+	/*
+	 * FIMXE: Need to replace this hack with proper seqlocks.
+	 *
+	 * Restrict the bump of the software vblank counter to a safe maximum
+	 * value of +1 whenever there is the possibility that concurrent readers
+	 * of vblank timestamps could be active at the moment, as the current
+	 * implementation of the timestamp caching and updating is not safe
+	 * against concurrent readers for calls to store_vblank() with a bump
+	 * of anything but +1. A bump != 1 would very likely return corrupted
+	 * timestamps to userspace, because the same slot in the cache could
+	 * be concurrently written by store_vblank() and read by one of those
+	 * readers without the read-retry logic detecting the collision.
+	 *
+	 * Concurrent readers can exist when we are called from the
+	 * drm_vblank_off() or drm_vblank_on() functions and other non-vblank-
+	 * irq callers. However, all those calls to us are happening with the
+	 * vbl_lock locked to prevent drm_vblank_get(), so the vblank refcount
+	 * can't increase while we are executing. Therefore a zero refcount at
+	 * this point is safe for arbitrary counter bumps if we are called
+	 * outside vblank irq, a non-zero count is not 100% safe. Unfortunately
+	 * we must also accept a refcount of 1, as whenever we are called from
+	 * drm_vblank_get() -> drm_vblank_enable() the refcount will be 1 and
+	 * we must let that one pass through in order to not lose vblank counts
+	 * during vblank irq off - which would completely defeat the whole
+	 * point of this routine.
+	 *
+	 * Whenever we are called from vblank irq, we have to assume concurrent
+	 * readers exist or can show up any time during our execution, even if
+	 * the refcount is currently zero, as vblank irqs are usually only
+	 * enabled due to the presence of readers, and because when we are called
+	 * from vblank irq we can't hold the vbl_lock to protect us from sudden
+	 * bumps in vblank refcount. Therefore also restrict bumps to +1 when
+	 * called from vblank irq.
+	 */
+	if ((diff > 1) && (atomic_read(&vblank->refcount) > 1 ||
+	    (flags & DRM_CALLED_FROM_VBLIRQ))) {
+		DRM_DEBUG_VBL("clamping vblank bump to 1 on crtc %u: diffr=%u "
+			      "refcount %u, vblirq %u\n", pipe, diff,
+			      atomic_read(&vblank->refcount),
+			      (flags & DRM_CALLED_FROM_VBLIRQ) != 0);
+		diff = 1;
+	}
+
 	DRM_DEBUG_VBL("updating vblank count on crtc %u:"
 		      " current=%u, diff=%u, hw=%u hw_last=%u\n",
 		      pipe, vblank->count, diff, cur_vblank, vblank->last);
@@ -983,15 +1041,12 @@ static void send_vblank_event(struct drm_device *dev,
 		struct drm_pending_vblank_event *e,
 		unsigned long seq, struct timeval *now)
 {
-	assert_spin_locked(&dev->event_lock);
-
 	e->event.sequence = seq;
 	e->event.tv_sec = now->tv_sec;
 	e->event.tv_usec = now->tv_usec;
 
-	list_add_tail(&e->base.link,
-		      &e->base.file_priv->event_list);
-	wake_up_interruptible(&e->base.file_priv->event_wait);
+	drm_send_event_locked(dev, &e->base);
+
 	trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
 					 e->event.sequence);
 }
@@ -1316,7 +1371,13 @@ void drm_vblank_off(struct drm_device *dev, unsigned int pipe)
 	spin_lock_irqsave(&dev->event_lock, irqflags);
 
 	spin_lock(&dev->vbl_lock);
-	vblank_disable_and_save(dev, pipe);
+	DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
+		      pipe, vblank->enabled, vblank->inmodeset);
+
+	/* Avoid redundant vblank disables without previous drm_vblank_on(). */
+	if (drm_core_check_feature(dev, DRIVER_ATOMIC) || !vblank->inmodeset)
+		vblank_disable_and_save(dev, pipe);
+
 	wake_up(&vblank->queue);
 
 	/*
@@ -1418,6 +1479,9 @@ void drm_vblank_on(struct drm_device *dev, unsigned int pipe)
 		return;
 
 	spin_lock_irqsave(&dev->vbl_lock, irqflags);
+	DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
+		      pipe, vblank->enabled, vblank->inmodeset);
+
 	/* Drop our private "prevent drm_vblank_get" refcount */
 	if (vblank->inmodeset) {
 		atomic_dec(&vblank->refcount);
@@ -1430,8 +1494,7 @@ void drm_vblank_on(struct drm_device *dev, unsigned int pipe)
 	 * re-enable interrupts if there are users left, or the
 	 * user wishes vblank interrupts to be enabled all the time.
 	 */
-	if (atomic_read(&vblank->refcount) != 0 ||
-	    (!dev->vblank_disable_immediate && drm_vblank_offdelay == 0))
+	if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0)
 		WARN_ON(drm_vblank_enable(dev, pipe));
 	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 }
@@ -1526,6 +1589,7 @@ void drm_vblank_post_modeset(struct drm_device *dev, unsigned int pipe)
 	if (vblank->inmodeset) {
 		spin_lock_irqsave(&dev->vbl_lock, irqflags);
 		dev->vblank_disable_allowed = true;
+		drm_reset_vblank_timestamp(dev, pipe);
 		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 
 		if (vblank->inmodeset & 0x2)
@@ -1601,9 +1665,6 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
 	e->event.base.type = DRM_EVENT_VBLANK;
 	e->event.base.length = sizeof(e->event);
 	e->event.user_data = vblwait->request.signal;
-	e->base.event = &e->event.base;
-	e->base.file_priv = file_priv;
-	e->base.destroy = (void (*) (struct drm_pending_event *)) kfree;
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 
@@ -1619,12 +1680,12 @@ static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe,
 		goto err_unlock;
 	}
 
-	if (file_priv->event_space < sizeof(e->event)) {
-		ret = -EBUSY;
+	ret = drm_event_reserve_init_locked(dev, file_priv, &e->base,
+					    &e->event.base);
+
+	if (ret)
 		goto err_unlock;
-	}
 
-	file_priv->event_space -= sizeof(e->event);
 	seq = drm_vblank_count_and_time(dev, pipe, &now);
 
 	if ((vblwait->request.type & _DRM_VBLANK_NEXTONMISS) &&