drm/vblank: Add support for precise vblank timestamping.
[linux-2.6.git] / drivers / gpu / drm / drm_irq.c
index 9d3a503..4e82d0d 100644 (file)
 #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);
@@ -599,7 +1061,6 @@ 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) {
@@ -609,7 +1070,8 @@ 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;
@@ -718,11 +1180,10 @@ 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 {
@@ -741,8 +1202,7 @@ 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);
 
@@ -780,11 +1240,64 @@ 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);