Merge remote branch 'airlied/drm-core-next' into drm-intel-next

1 files changed, 538 insertions, 25 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 722700d5d73e..77c875db5aae 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -40,6 +40,22 @@
 #include <linux/slab.h>
 
 #include <linux/vgaarb.h>
+
+/* Access macro for slots in vblank timestamp ringbuffer. */
+#define vblanktimestamp(dev, crtc, count) ( \
+	(dev)->_vblank_time[(crtc) * DRM_VBLANKTIME_RBSIZE + \
+	((count) % DRM_VBLANKTIME_RBSIZE)])
+
+/* Retry timestamp calculation up to 3 times to satisfy
+ * drm_timestamp_precision before giving up.
+ */
+#define DRM_TIMESTAMP_MAXRETRIES 3
+
+/* Threshold in nanoseconds for detection of redundant
+ * vblank irq in drm_handle_vblank(). 1 msec should be ok.
+ */
+#define DRM_REDUNDANT_VBLIRQ_THRESH_NS 1000000
+
 /**
  * Get interrupt from bus id.
  *
@@ -77,6 +93,87 @@ int drm_irq_by_busid(struct drm_device *dev, void *data,
 	return 0;
 }
 
+/*
+ * Clear vblank timestamp buffer for a crtc.
+ */
+static void clear_vblank_timestamps(struct drm_device *dev, int crtc)
+{
+	memset(&dev->_vblank_time[crtc * DRM_VBLANKTIME_RBSIZE], 0,
+		DRM_VBLANKTIME_RBSIZE * sizeof(struct timeval));
+}
+
+/*
+ * Disable vblank irq's on crtc, make sure that last vblank count
+ * of hardware and corresponding consistent software vblank counter
+ * are preserved, even if there are any spurious vblank irq's after
+ * disable.
+ */
+static void vblank_disable_and_save(struct drm_device *dev, int crtc)
+{
+	unsigned long irqflags;
+	u32 vblcount;
+	s64 diff_ns;
+	int vblrc;
+	struct timeval tvblank;
+
+	/* Prevent vblank irq processing while disabling vblank irqs,
+	 * so no updates of timestamps or count can happen after we've
+	 * disabled. Needed to prevent races in case of delayed irq's.
+	 * Disable preemption, so vblank_time_lock is held as short as
+	 * possible, even under a kernel with PREEMPT_RT patches.
+	 */
+	preempt_disable();
+	spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
+
+	dev->driver->disable_vblank(dev, crtc);
+	dev->vblank_enabled[crtc] = 0;
+
+	/* No further vblank irq's will be processed after
+	 * this point. Get current hardware vblank count and
+	 * vblank timestamp, repeat until they are consistent.
+	 *
+	 * FIXME: There is still a race condition here and in
+	 * drm_update_vblank_count() which can cause off-by-one
+	 * reinitialization of software vblank counter. If gpu
+	 * vblank counter doesn't increment exactly at the leading
+	 * edge of a vblank interval, then we can lose 1 count if
+	 * we happen to execute between start of vblank and the
+	 * delayed gpu counter increment.
+	 */
+	do {
+		dev->last_vblank[crtc] = dev->driver->get_vblank_counter(dev, crtc);
+		vblrc = drm_get_last_vbltimestamp(dev, crtc, &tvblank, 0);
+	} while (dev->last_vblank[crtc] != dev->driver->get_vblank_counter(dev, crtc));
+
+	/* Compute time difference to stored timestamp of last vblank
+	 * as updated by last invocation of drm_handle_vblank() in vblank irq.
+	 */
+	vblcount = atomic_read(&dev->_vblank_count[crtc]);
+	diff_ns = timeval_to_ns(&tvblank) -
+		  timeval_to_ns(&vblanktimestamp(dev, crtc, vblcount));
+
+	/* If there is at least 1 msec difference between the last stored
+	 * timestamp and tvblank, then we are currently executing our
+	 * disable inside a new vblank interval, the tvblank timestamp
+	 * corresponds to this new vblank interval and the irq handler
+	 * for this vblank didn't run yet and won't run due to our disable.
+	 * Therefore we need to do the job of drm_handle_vblank() and
+	 * increment the vblank counter by one to account for this vblank.
+	 *
+	 * Skip this step if there isn't any high precision timestamp
+	 * available. In that case we can't account for this and just
+	 * hope for the best.
+	 */
+	if ((vblrc > 0) && (abs(diff_ns) > 1000000))
+		atomic_inc(&dev->_vblank_count[crtc]);
+
+	/* Invalidate all timestamps while vblank irq's are off. */
+	clear_vblank_timestamps(dev, crtc);
+
+	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
+	preempt_enable();
+}
+
 static void vblank_disable_fn(unsigned long arg)
 {
 	struct drm_device *dev = (struct drm_device *)arg;
@@ -91,10 +188,7 @@ static void vblank_disable_fn(unsigned long arg)
 		if (atomic_read(&dev->vblank_refcount[i]) == 0 &&
 		    dev->vblank_enabled[i]) {
 			DRM_DEBUG("disabling vblank on crtc %d\n", i);
-			dev->last_vblank[i] =
-				dev->driver->get_vblank_counter(dev, i);
-			dev->driver->disable_vblank(dev, i);
-			dev->vblank_enabled[i] = 0;
+			vblank_disable_and_save(dev, i);
 		}
 		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 	}
@@ -117,6 +211,7 @@ void drm_vblank_cleanup(struct drm_device *dev)
 	kfree(dev->last_vblank);
 	kfree(dev->last_vblank_wait);
 	kfree(dev->vblank_inmodeset);
+	kfree(dev->_vblank_time);
 
 	dev->num_crtcs = 0;
 }
@@ -129,6 +224,8 @@ int drm_vblank_init(struct drm_device *dev, int num_crtcs)
 	setup_timer(&dev->vblank_disable_timer, vblank_disable_fn,
 		    (unsigned long)dev);
 	spin_lock_init(&dev->vbl_lock);
+	spin_lock_init(&dev->vblank_time_lock);
+
 	dev->num_crtcs = num_crtcs;
 
 	dev->vbl_queue = kmalloc(sizeof(wait_queue_head_t) * num_crtcs,
@@ -161,6 +258,19 @@ int drm_vblank_init(struct drm_device *dev, int num_crtcs)
 	if (!dev->vblank_inmodeset)
 		goto err;
 
+	dev->_vblank_time = kcalloc(num_crtcs * DRM_VBLANKTIME_RBSIZE,
+				    sizeof(struct timeval), GFP_KERNEL);
+	if (!dev->_vblank_time)
+		goto err;
+
+	DRM_INFO("Supports vblank timestamp caching Rev 1 (10.10.2010).\n");
+
+	/* Driver specific high-precision vblank timestamping supported? */
+	if (dev->driver->get_vblank_timestamp)
+		DRM_INFO("Driver supports precise vblank timestamp query.\n");
+	else
+		DRM_INFO("No driver support for vblank timestamp query.\n");
+
 	/* Zero per-crtc vblank stuff */
 	for (i = 0; i < num_crtcs; i++) {
 		init_waitqueue_head(&dev->vbl_queue[i]);
@@ -279,7 +389,7 @@ EXPORT_SYMBOL(drm_irq_install);
  *
  * Calls the driver's \c drm_driver_irq_uninstall() function, and stops the irq.
  */
-int drm_irq_uninstall(struct drm_device * dev)
+int drm_irq_uninstall(struct drm_device *dev)
 {
 	unsigned long irqflags;
 	int irq_enabled, i;
@@ -335,7 +445,9 @@ int drm_control(struct drm_device *dev, void *data,
 {
 	struct drm_control *ctl = data;
 
-	/* if we haven't irq we fallback for compatibility reasons - this used to be a separate function in drm_dma.h */
+	/* if we haven't irq we fallback for compatibility reasons -
+	 * this used to be a separate function in drm_dma.h
+	 */
 
 
 	switch (ctl->func) {
@@ -360,6 +472,287 @@ int drm_control(struct drm_device *dev, void *data,
 }
 
 /**
+ * drm_calc_timestamping_constants - Calculate and
+ * store various constants which are later needed by
+ * vblank and swap-completion timestamping, e.g, by
+ * drm_calc_vbltimestamp_from_scanoutpos().
+ * They are derived from crtc's true scanout timing,
+ * so they take things like panel scaling or other
+ * adjustments into account.
+ *
+ * @crtc drm_crtc whose timestamp constants should be updated.
+ *
+ */
+void drm_calc_timestamping_constants(struct drm_crtc *crtc)
+{
+	s64 linedur_ns = 0, pixeldur_ns = 0, framedur_ns = 0;
+	u64 dotclock;
+
+	/* Dot clock in Hz: */
+	dotclock = (u64) crtc->hwmode.clock * 1000;
+
+	/* Valid dotclock? */
+	if (dotclock > 0) {
+		/* Convert scanline length in pixels and video dot clock to
+		 * line duration, frame duration and pixel duration in
+		 * nanoseconds:
+		 */
+		pixeldur_ns = (s64) div64_u64(1000000000, dotclock);
+		linedur_ns  = (s64) div64_u64(((u64) crtc->hwmode.crtc_htotal *
+					      1000000000), dotclock);
+		framedur_ns = (s64) crtc->hwmode.crtc_vtotal * linedur_ns;
+	} else
+		DRM_ERROR("crtc %d: Can't calculate constants, dotclock = 0!\n",
+			  crtc->base.id);
+
+	crtc->pixeldur_ns = pixeldur_ns;
+	crtc->linedur_ns  = linedur_ns;
+	crtc->framedur_ns = framedur_ns;
+
+	DRM_DEBUG("crtc %d: hwmode: htotal %d, vtotal %d, vdisplay %d\n",
+		  crtc->base.id, crtc->hwmode.crtc_htotal,
+		  crtc->hwmode.crtc_vtotal, crtc->hwmode.crtc_vdisplay);
+	DRM_DEBUG("crtc %d: clock %d kHz framedur %d linedur %d, pixeldur %d\n",
+		  crtc->base.id, (int) dotclock/1000, (int) framedur_ns,
+		  (int) linedur_ns, (int) pixeldur_ns);
+}
+EXPORT_SYMBOL(drm_calc_timestamping_constants);
+
+/**
+ * drm_calc_vbltimestamp_from_scanoutpos - helper routine for kms
+ * drivers. Implements calculation of exact vblank timestamps from
+ * given drm_display_mode timings and current video scanout position
+ * of a crtc. This can be called from within get_vblank_timestamp()
+ * implementation of a kms driver to implement the actual timestamping.
+ *
+ * Should return timestamps conforming to the OML_sync_control OpenML
+ * extension specification. The timestamp corresponds to the end of
+ * the vblank interval, aka start of scanout of topmost-leftmost display
+ * pixel in the following video frame.
+ *
+ * Requires support for optional dev->driver->get_scanout_position()
+ * in kms driver, plus a bit of setup code to provide a drm_display_mode
+ * that corresponds to the true scanout timing.
+ *
+ * The current implementation only handles standard video modes. It
+ * returns as no operation if a doublescan or interlaced video mode is
+ * active. Higher level code is expected to handle this.
+ *
+ * @dev: DRM device.
+ * @crtc: Which crtc's vblank timestamp to retrieve.
+ * @max_error: Desired maximum allowable error in timestamps (nanosecs).
+ *             On return contains true maximum error of timestamp.
+ * @vblank_time: Pointer to struct timeval which should receive the timestamp.
+ * @flags: Flags to pass to driver:
+ *         0 = Default.
+ *         DRM_CALLED_FROM_VBLIRQ = If function is called from vbl irq handler.
+ * @refcrtc: drm_crtc* of crtc which defines scanout timing.
+ *
+ * Returns negative value on error, failure or if not supported in current
+ * video mode:
+ *
+ * -EINVAL   - Invalid crtc.
+ * -EAGAIN   - Temporary unavailable, e.g., called before initial modeset.
+ * -ENOTSUPP - Function not supported in current display mode.
+ * -EIO      - Failed, e.g., due to failed scanout position query.
+ *
+ * Returns or'ed positive status flags on success:
+ *
+ * DRM_VBLANKTIME_SCANOUTPOS_METHOD - Signal this method used for timestamping.
+ * DRM_VBLANKTIME_INVBL - Timestamp taken while scanout was in vblank interval.
+ *
+ */
+int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, int crtc,
+					  int *max_error,
+					  struct timeval *vblank_time,
+					  unsigned flags,
+					  struct drm_crtc *refcrtc)
+{
+	struct timeval stime, raw_time;
+	struct drm_display_mode *mode;
+	int vbl_status, vtotal, vdisplay;
+	int vpos, hpos, i;
+	s64 framedur_ns, linedur_ns, pixeldur_ns, delta_ns, duration_ns;
+	bool invbl;
+
+	if (crtc < 0 || crtc >= dev->num_crtcs) {
+		DRM_ERROR("Invalid crtc %d\n", crtc);
+		return -EINVAL;
+	}
+
+	/* Scanout position query not supported? Should not happen. */
+	if (!dev->driver->get_scanout_position) {
+		DRM_ERROR("Called from driver w/o get_scanout_position()!?\n");
+		return -EIO;
+	}
+
+	mode = &refcrtc->hwmode;
+	vtotal = mode->crtc_vtotal;
+	vdisplay = mode->crtc_vdisplay;
+
+	/* Durations of frames, lines, pixels in nanoseconds. */
+	framedur_ns = refcrtc->framedur_ns;
+	linedur_ns  = refcrtc->linedur_ns;
+	pixeldur_ns = refcrtc->pixeldur_ns;
+
+	/* If mode timing undefined, just return as no-op:
+	 * Happens during initial modesetting of a crtc.
+	 */
+	if (vtotal <= 0 || vdisplay <= 0 || framedur_ns == 0) {
+		DRM_DEBUG("crtc %d: Noop due to uninitialized mode.\n", crtc);
+		return -EAGAIN;
+	}
+
+	/* Don't know yet how to handle interlaced or
+	 * double scan modes. Just no-op for now.
+	 */
+	if (mode->flags & (DRM_MODE_FLAG_INTERLACE | DRM_MODE_FLAG_DBLSCAN)) {
+		DRM_DEBUG("crtc %d: Noop due to unsupported mode.\n", crtc);
+		return -ENOTSUPP;
+	}
+
+	/* Get current scanout position with system timestamp.
+	 * Repeat query up to DRM_TIMESTAMP_MAXRETRIES times
+	 * if single query takes longer than max_error nanoseconds.
+	 *
+	 * This guarantees a tight bound on maximum error if
+	 * code gets preempted or delayed for some reason.
+	 */
+	for (i = 0; i < DRM_TIMESTAMP_MAXRETRIES; i++) {
+		/* Disable preemption to make it very likely to
+		 * succeed in the first iteration even on PREEMPT_RT kernel.
+		 */
+		preempt_disable();
+
+		/* Get system timestamp before query. */
+		do_gettimeofday(&stime);
+
+		/* Get vertical and horizontal scanout pos. vpos, hpos. */
+		vbl_status = dev->driver->get_scanout_position(dev, crtc, &vpos, &hpos);
+
+		/* Get system timestamp after query. */
+		do_gettimeofday(&raw_time);
+
+		preempt_enable();
+
+		/* Return as no-op if scanout query unsupported or failed. */
+		if (!(vbl_status & DRM_SCANOUTPOS_VALID)) {
+			DRM_DEBUG("crtc %d : scanoutpos query failed [%d].\n",
+				  crtc, vbl_status);
+			return -EIO;
+		}
+
+		duration_ns = timeval_to_ns(&raw_time) - timeval_to_ns(&stime);
+
+		/* Accept result with <  max_error nsecs timing uncertainty. */
+		if (duration_ns <= (s64) *max_error)
+			break;
+	}
+
+	/* Noisy system timing? */
+	if (i == DRM_TIMESTAMP_MAXRETRIES) {
+		DRM_DEBUG("crtc %d: Noisy timestamp %d us > %d us [%d reps].\n",
+			  crtc, (int) duration_ns/1000, *max_error/1000, i);
+	}
+
+	/* Return upper bound of timestamp precision error. */
+	*max_error = (int) duration_ns;
+
+	/* Check if in vblank area:
+	 * vpos is >=0 in video scanout area, but negative
+	 * within vblank area, counting down the number of lines until
+	 * start of scanout.
+	 */
+	invbl = vbl_status & DRM_SCANOUTPOS_INVBL;
+
+	/* Convert scanout position into elapsed time at raw_time query
+	 * since start of scanout at first display scanline. delta_ns
+	 * can be negative if start of scanout hasn't happened yet.
+	 */
+	delta_ns = (s64) vpos * linedur_ns + (s64) hpos * pixeldur_ns;
+
+	/* Is vpos outside nominal vblank area, but less than
+	 * 1/100 of a frame height away from start of vblank?
+	 * If so, assume this isn't a massively delayed vblank
+	 * interrupt, but a vblank interrupt that fired a few
+	 * microseconds before true start of vblank. Compensate
+	 * by adding a full frame duration to the final timestamp.
+	 * Happens, e.g., on ATI R500, R600.
+	 *
+	 * We only do this if DRM_CALLED_FROM_VBLIRQ.
+	 */
+	if ((flags & DRM_CALLED_FROM_VBLIRQ) && !invbl &&
+	    ((vdisplay - vpos) < vtotal / 100)) {
+		delta_ns = delta_ns - framedur_ns;
+
+		/* Signal this correction as "applied". */
+		vbl_status |= 0x8;
+	}
+
+	/* Subtract time delta from raw timestamp to get final
+	 * vblank_time timestamp for end of vblank.
+	 */
+	*vblank_time = ns_to_timeval(timeval_to_ns(&raw_time) - delta_ns);
+
+	DRM_DEBUG("crtc %d : v %d p(%d,%d)@ %d.%d -> %d.%d [e %d us, %d rep]\n",
+		  crtc, (int) vbl_status, hpos, vpos, raw_time.tv_sec,
+		  raw_time.tv_usec, vblank_time->tv_sec, vblank_time->tv_usec,
+		  (int) duration_ns/1000, i);
+
+	vbl_status = DRM_VBLANKTIME_SCANOUTPOS_METHOD;
+	if (invbl)
+		vbl_status |= DRM_VBLANKTIME_INVBL;
+
+	return vbl_status;
+}
+EXPORT_SYMBOL(drm_calc_vbltimestamp_from_scanoutpos);
+
+/**
+ * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
+ * vblank interval.
+ *
+ * @dev: DRM device
+ * @crtc: which crtc's vblank timestamp to retrieve
+ * @tvblank: Pointer to target struct timeval which should receive the timestamp
+ * @flags: Flags to pass to driver:
+ *         0 = Default.
+ *         DRM_CALLED_FROM_VBLIRQ = If function is called from vbl irq handler.
+ *
+ * Fetches the system timestamp corresponding to the time of the most recent
+ * vblank interval on specified crtc. May call into kms-driver to
+ * compute the timestamp with a high-precision GPU specific method.
+ *
+ * Returns zero if timestamp originates from uncorrected do_gettimeofday()
+ * call, i.e., it isn't very precisely locked to the true vblank.
+ *
+ * Returns non-zero if timestamp is considered to be very precise.
+ */
+u32 drm_get_last_vbltimestamp(struct drm_device *dev, int crtc,
+			      struct timeval *tvblank, unsigned flags)
+{
+	int ret = 0;
+
+	/* Define requested maximum error on timestamps (nanoseconds). */
+	int max_error = (int) drm_timestamp_precision * 1000;
+
+	/* Query driver if possible and precision timestamping enabled. */
+	if (dev->driver->get_vblank_timestamp && (max_error > 0)) {
+		ret = dev->driver->get_vblank_timestamp(dev, crtc, &max_error,
+							tvblank, flags);
+		if (ret > 0)
+			return (u32) ret;
+	}
+
+	/* GPU high precision timestamp query unsupported or failed.
+	 * Return gettimeofday timestamp as best estimate.
+	 */
+	do_gettimeofday(tvblank);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_get_last_vbltimestamp);
+
+/**
  * drm_vblank_count - retrieve "cooked" vblank counter value
  * @dev: DRM device
  * @crtc: which counter to retrieve
@@ -375,6 +768,40 @@ u32 drm_vblank_count(struct drm_device *dev, int crtc)
 EXPORT_SYMBOL(drm_vblank_count);
 
 /**
+ * drm_vblank_count_and_time - retrieve "cooked" vblank counter value
+ * and the system timestamp corresponding to that vblank counter value.
+ *
+ * @dev: DRM device
+ * @crtc: which counter to retrieve
+ * @vblanktime: Pointer to struct timeval to receive the vblank timestamp.
+ *
+ * Fetches the "cooked" vblank count value that represents the number of
+ * vblank events since the system was booted, including lost events due to
+ * modesetting activity. Returns corresponding system timestamp of the time
+ * of the vblank interval that corresponds to the current value vblank counter
+ * value.
+ */
+u32 drm_vblank_count_and_time(struct drm_device *dev, int crtc,
+			      struct timeval *vblanktime)
+{
+	u32 cur_vblank;
+
+	/* Read timestamp from slot of _vblank_time ringbuffer
+	 * that corresponds to current vblank count. Retry if
+	 * count has incremented during readout. This works like
+	 * a seqlock.
+	 */
+	do {
+		cur_vblank = atomic_read(&dev->_vblank_count[crtc]);
+		*vblanktime = vblanktimestamp(dev, crtc, cur_vblank);
+		smp_rmb();
+	} while (cur_vblank != atomic_read(&dev->_vblank_count[crtc]));
+
+	return cur_vblank;
+}
+EXPORT_SYMBOL(drm_vblank_count_and_time);
+
+/**
  * drm_update_vblank_count - update the master vblank counter
  * @dev: DRM device
  * @crtc: counter to update
@@ -392,7 +819,8 @@ EXPORT_SYMBOL(drm_vblank_count);
  */
 static void drm_update_vblank_count(struct drm_device *dev, int crtc)
 {
-	u32 cur_vblank, diff;
+	u32 cur_vblank, diff, tslot, rc;
+	struct timeval t_vblank;
 
 	/*
 	 * Interrupts were disabled prior to this call, so deal with counter
@@ -400,8 +828,18 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
 	 * NOTE!  It's possible we lost a full dev->max_vblank_count events
 	 * here if the register is small or we had vblank interrupts off for
 	 * a long time.
+	 *
+	 * We repeat the hardware vblank counter & timestamp query until
+	 * we get consistent results. This to prevent races between gpu
+	 * updating its hardware counter while we are retrieving the
+	 * corresponding vblank timestamp.
 	 */
-	cur_vblank = dev->driver->get_vblank_counter(dev, crtc);
+	do {
+		cur_vblank = dev->driver->get_vblank_counter(dev, crtc);
+		rc = drm_get_last_vbltimestamp(dev, crtc, &t_vblank, 0);
+	} while (cur_vblank != dev->driver->get_vblank_counter(dev, crtc));
+
+	/* Deal with counter wrap */
 	diff = cur_vblank - dev->last_vblank[crtc];
 	if (cur_vblank < dev->last_vblank[crtc]) {
 		diff += dev->max_vblank_count;
@@ -413,6 +851,16 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
 	DRM_DEBUG("enabling vblank interrupts on crtc %d, missed %d\n",
 		  crtc, diff);
 
+	/* Reinitialize corresponding vblank timestamp if high-precision query
+	 * available. Skip this step if query unsupported or failed. Will
+	 * reinitialize delayed at next vblank interrupt in that case.
+	 */
+	if (rc) {
+		tslot = atomic_read(&dev->_vblank_count[crtc]) + diff;
+		vblanktimestamp(dev, crtc, tslot) = t_vblank;
+		smp_wmb();
+	}
+
 	atomic_add(diff, &dev->_vblank_count[crtc]);
 }
 
@@ -429,15 +877,27 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
  */
 int drm_vblank_get(struct drm_device *dev, int crtc)
 {
-	unsigned long irqflags;
+	unsigned long irqflags, irqflags2;
 	int ret = 0;
 
 	spin_lock_irqsave(&dev->vbl_lock, irqflags);
 	/* Going from 0->1 means we have to enable interrupts again */
 	if (atomic_add_return(1, &dev->vblank_refcount[crtc]) == 1) {
+		/* Disable preemption while holding vblank_time_lock. Do
+		 * it explicitely to guard against PREEMPT_RT kernel.
+		 */
+		preempt_disable();
+		spin_lock_irqsave(&dev->vblank_time_lock, irqflags2);
 		if (!dev->vblank_enabled[crtc]) {
+			/* Enable vblank irqs under vblank_time_lock protection.
+			 * All vblank count & timestamp updates are held off
+			 * until we are done reinitializing master counter and
+			 * timestamps. Filtercode in drm_handle_vblank() will
+			 * prevent double-accounting of same vblank interval.
+			 */
 			ret = dev->driver->enable_vblank(dev, crtc);
-			DRM_DEBUG("enabling vblank on crtc %d, ret: %d\n", crtc, ret);
+			DRM_DEBUG("enabling vblank on crtc %d, ret: %d\n",
+				  crtc, ret);
 			if (ret)
 				atomic_dec(&dev->vblank_refcount[crtc]);
 			else {
@@ -445,6 +905,8 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
 				drm_update_vblank_count(dev, crtc);
 			}
 		}
+		spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags2);
+		preempt_enable();
 	} else {
 		if (!dev->vblank_enabled[crtc]) {
 			atomic_dec(&dev->vblank_refcount[crtc]);
@@ -463,15 +925,17 @@ EXPORT_SYMBOL(drm_vblank_get);
  * @crtc: which counter to give up
  *
  * Release ownership of a given vblank counter, turning off interrupts
- * if possible.
+ * if possible. Disable interrupts after drm_vblank_offdelay milliseconds.
  */
 void drm_vblank_put(struct drm_device *dev, int crtc)
 {
-	BUG_ON (atomic_read (&dev->vblank_refcount[crtc]) == 0);
+	BUG_ON(atomic_read(&dev->vblank_refcount[crtc]) == 0);
 
 	/* Last user schedules interrupt disable */
-	if (atomic_dec_and_test(&dev->vblank_refcount[crtc]))
-		mod_timer(&dev->vblank_disable_timer, jiffies + 5*DRM_HZ);
+	if (atomic_dec_and_test(&dev->vblank_refcount[crtc]) &&
+	    (drm_vblank_offdelay > 0))
+		mod_timer(&dev->vblank_disable_timer,
+			  jiffies + ((drm_vblank_offdelay * DRM_HZ)/1000));
 }
 EXPORT_SYMBOL(drm_vblank_put);
 
@@ -480,10 +944,8 @@ void drm_vblank_off(struct drm_device *dev, int crtc)
 	unsigned long irqflags;
 
 	spin_lock_irqsave(&dev->vbl_lock, irqflags);
-	dev->driver->disable_vblank(dev, crtc);
+	vblank_disable_and_save(dev, crtc);
 	DRM_WAKEUP(&dev->vbl_queue[crtc]);
-	dev->vblank_enabled[crtc] = 0;
-	dev->last_vblank[crtc] = dev->driver->get_vblank_counter(dev, crtc);
 	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 }
 EXPORT_SYMBOL(drm_vblank_off);
@@ -602,7 +1064,6 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
 	e->base.file_priv = file_priv;
 	e->base.destroy = (void (*) (struct drm_pending_event *)) kfree;
 
-	do_gettimeofday(&now);
 	spin_lock_irqsave(&dev->event_lock, flags);
 
 	if (file_priv->event_space < sizeof e->event) {
@@ -611,7 +1072,8 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
 	}
 
 	file_priv->event_space -= sizeof e->event;
-	seq = drm_vblank_count(dev, pipe);
+	seq = drm_vblank_count_and_time(dev, pipe, &now);
+
 	if ((vblwait->request.type & _DRM_VBLANK_NEXTONMISS) &&
 	    (seq - vblwait->request.sequence) <= (1 << 23)) {
 		vblwait->request.sequence = seq + 1;
@@ -727,11 +1189,10 @@ int drm_wait_vblank(struct drm_device *dev, void *data,
 	if (ret != -EINTR) {
 		struct timeval now;
 
-		do_gettimeofday(&now);
-
+		vblwait->reply.sequence = drm_vblank_count_and_time(dev, crtc, &now);
 		vblwait->reply.tval_sec = now.tv_sec;
 		vblwait->reply.tval_usec = now.tv_usec;
-		vblwait->reply.sequence = drm_vblank_count(dev, crtc);
+
 		DRM_DEBUG("returning %d to client\n",
 			  vblwait->reply.sequence);
 	} else {
@@ -750,8 +1211,7 @@ void drm_handle_vblank_events(struct drm_device *dev, int crtc)
 	unsigned long flags;
 	unsigned int seq;
 
-	do_gettimeofday(&now);
-	seq = drm_vblank_count(dev, crtc);
+	seq = drm_vblank_count_and_time(dev, crtc, &now);
 
 	spin_lock_irqsave(&dev->event_lock, flags);
 
@@ -789,11 +1249,64 @@ void drm_handle_vblank_events(struct drm_device *dev, int crtc)
  */
 void drm_handle_vblank(struct drm_device *dev, int crtc)
 {
+	u32 vblcount;
+	s64 diff_ns;
+	struct timeval tvblank;
+	unsigned long irqflags;
+
 	if (!dev->num_crtcs)
 		return;
 
-	atomic_inc(&dev->_vblank_count[crtc]);
+	/* Need timestamp lock to prevent concurrent execution with
+	 * vblank enable/disable, as this would cause inconsistent
+	 * or corrupted timestamps and vblank counts.
+	 */
+	spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
+
+	/* Vblank irq handling disabled. Nothing to do. */
+	if (!dev->vblank_enabled[crtc]) {
+		spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
+		return;
+	}
+
+	/* Fetch corresponding timestamp for this vblank interval from
+	 * driver and store it in proper slot of timestamp ringbuffer.
+	 */
+
+	/* Get current timestamp and count. */
+	vblcount = atomic_read(&dev->_vblank_count[crtc]);
+	drm_get_last_vbltimestamp(dev, crtc, &tvblank, DRM_CALLED_FROM_VBLIRQ);
+
+	/* Compute time difference to timestamp of last vblank */
+	diff_ns = timeval_to_ns(&tvblank) -
+		  timeval_to_ns(&vblanktimestamp(dev, crtc, vblcount));
+
+	/* Update vblank timestamp and count if at least
+	 * DRM_REDUNDANT_VBLIRQ_THRESH_NS nanoseconds
+	 * difference between last stored timestamp and current
+	 * timestamp. A smaller difference means basically
+	 * identical timestamps. Happens if this vblank has
+	 * been already processed and this is a redundant call,
+	 * e.g., due to spurious vblank interrupts. We need to
+	 * ignore those for accounting.
+	 */
+	if (abs(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
+		/* Store new timestamp in ringbuffer. */
+		vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;
+		smp_wmb();
+
+		/* Increment cooked vblank count. This also atomically commits
+		 * the timestamp computed above.
+		 */
+		atomic_inc(&dev->_vblank_count[crtc]);
+	} else {
+		DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n",
+			  crtc, (int) diff_ns);
+	}
+
 	DRM_WAKEUP(&dev->vbl_queue[crtc]);
 	drm_handle_vblank_events(dev, crtc);
+
+	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
 }
 EXPORT_SYMBOL(drm_handle_vblank);