5 files changed, 662 insertions, 26 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index f7af91cb273d..4c200931a6bc 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -336,7 +336,7 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
                               struct drm_framebuffer *old_fb)
 {
         struct drm_device *dev = crtc->dev;
-        struct drm_display_mode *adjusted_mode, saved_mode;
+        struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode;
         struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
         struct drm_encoder_helper_funcs *encoder_funcs;
         int saved_x, saved_y;
@@ -350,6 +350,7 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
         if (!crtc->enabled)
                 return true;
 
+        saved_hwmode = crtc->hwmode;
         saved_mode = crtc->mode;
         saved_x = crtc->x;
         saved_y = crtc->y;
@@ -427,11 +428,21 @@ bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
 
         }
 
+        /* Store real post-adjustment hardware mode. */
+        crtc->hwmode = *adjusted_mode;
+
+        /* Calculate and store various constants which
+         * are later needed by vblank and swap-completion
+         * timestamping. They are derived from true hwmode.
+         */
+        drm_calc_timestamping_constants(crtc);
+
         /* XXX free adjustedmode */
         drm_mode_destroy(dev, adjusted_mode);
         /* FIXME: add subpixel order */
 done:
         if (!ret) {
+                crtc->hwmode = saved_hwmode;
                 crtc->mode = saved_mode;
                 crtc->x = saved_x;
                 crtc->y = saved_y;
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 9d3a5030b6e1..4e82d0d3c378 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);
@@ -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);
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index cdc89ee042cc..d59edc18301f 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -40,12 +40,22 @@
 unsigned int drm_debug = 0;     /* 1 to enable debug output */
 EXPORT_SYMBOL(drm_debug);
 
+unsigned int drm_vblank_offdelay = 5000;    /* Default to 5000 msecs. */
+EXPORT_SYMBOL(drm_vblank_offdelay);
+
+unsigned int drm_timestamp_precision = 20;  /* Default to 20 usecs. */
+EXPORT_SYMBOL(drm_timestamp_precision);
+
 MODULE_AUTHOR(CORE_AUTHOR);
 MODULE_DESCRIPTION(CORE_DESC);
 MODULE_LICENSE("GPL and additional rights");
 MODULE_PARM_DESC(debug, "Enable debug output");
+MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs]");
+MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");
 
 module_param_named(debug, drm_debug, int, 0600);
+module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
+module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
 
 struct idr drm_minors_idr;
 
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 274eaaa15c36..2b3398004aa5 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -683,6 +683,21 @@ struct drm_master {
         void *driver_priv; /**< Private structure for driver to use */
 };
 
+/* Size of ringbuffer for vblank timestamps. Just double-buffer
+ * in initial implementation.
+ */
+#define DRM_VBLANKTIME_RBSIZE 2
+
+/* Flags and return codes for get_vblank_timestamp() driver function. */
+#define DRM_CALLED_FROM_VBLIRQ 1
+#define DRM_VBLANKTIME_SCANOUTPOS_METHOD (1 << 0)
+#define DRM_VBLANKTIME_INVBL             (1 << 1)
+
+/* get_scanout_position() return flags */
+#define DRM_SCANOUTPOS_VALID        (1 << 0)
+#define DRM_SCANOUTPOS_INVBL        (1 << 1)
+#define DRM_SCANOUTPOS_ACCURATE     (1 << 2)
+
 /**
  * DRM driver structure. This structure represent the common code for
  * a family of cards. There will one drm_device for each card present
@@ -760,6 +775,68 @@ struct drm_driver {
          */
         int (*device_is_agp) (struct drm_device *dev);
 
+        /**
+         * Called by vblank timestamping code.
+         *
+         * Return the current display scanout position from a crtc.
+         *
+         * \param dev  DRM device.
+         * \param crtc Id of the crtc to query.
+         * \param *vpos Target location for current vertical scanout position.
+         * \param *hpos Target location for current horizontal scanout position.
+         *
+         * Returns vpos as a positive number while in active scanout area.
+         * Returns vpos as a negative number inside vblank, counting the number
+         * of scanlines to go until end of vblank, e.g., -1 means "one scanline
+         * until start of active scanout / end of vblank."
+         *
+         * \return Flags, or'ed together as follows:
+         *
+         * DRM_SCANOUTPOS_VALID = Query successfull.
+         * DRM_SCANOUTPOS_INVBL = Inside vblank.
+         * DRM_SCANOUTPOS_ACCURATE = Returned position is accurate. A lack of
+         * this flag means that returned position may be offset by a constant
+         * but unknown small number of scanlines wrt. real scanout position.
+         *
+         */
+        int (*get_scanout_position) (struct drm_device *dev, int crtc,
+                                     int *vpos, int *hpos);
+
+        /**
+         * Called by \c drm_get_last_vbltimestamp. Should return a precise
+         * timestamp when the most recent VBLANK interval ended or will end.
+         *
+         * Specifically, the timestamp in @vblank_time should correspond as
+         * closely as possible to the time when the first video scanline of
+         * the video frame after the end of VBLANK will start scanning out,
+         * the time immmediately after end of the VBLANK interval. If the
+         * @crtc is currently inside VBLANK, this will be a time in the future.
+         * If the @crtc is currently scanning out a frame, this will be the
+         * past start time of the current scanout. This is meant to adhere
+         * to the OpenML OML_sync_control extension specification.
+         *
+         * \param dev dev DRM device handle.
+         * \param crtc crtc for which timestamp should be returned.
+         * \param *max_error Maximum allowable timestamp error in nanoseconds.
+         *                   Implementation should strive to provide timestamp
+         *                   with an error of at most *max_error nanoseconds.
+         *                   Returns true upper bound on error for timestamp.
+         * \param *vblank_time Target location for returned vblank timestamp.
+         * \param flags 0 = Defaults, no special treatment needed.
+         * \param       DRM_CALLED_FROM_VBLIRQ = Function is called from vblank
+         *              irq handler. Some drivers need to apply some workarounds
+         *              for gpu-specific vblank irq quirks if flag is set.
+         *
+         * \returns
+         * Zero if timestamping isn't supported in current display mode or a
+         * negative number on failure. A positive status code on success,
+         * which describes how the vblank_time timestamp was computed.
+         */
+        int (*get_vblank_timestamp) (struct drm_device *dev, int crtc,
+                                     int *max_error,
+                                     struct timeval *vblank_time,
+                                     unsigned flags);
+
         /* these have to be filled in */
 
         irqreturn_t(*irq_handler) (DRM_IRQ_ARGS);
@@ -983,6 +1060,8 @@ struct drm_device {
 
         wait_queue_head_t *vbl_queue;   /**< VBLANK wait queue */
         atomic_t *_vblank_count;        /**< number of VBLANK interrupts (driver must alloc the right number of counters) */
+        struct timeval *_vblank_time;   /**< timestamp of current vblank_count (drivers must alloc right number of fields) */
+        spinlock_t vblank_time_lock;    /**< Protects vblank count and time updates during vblank enable/disable */
         spinlock_t vbl_lock;
         atomic_t *vblank_refcount;      /* number of users of vblank interruptsper crtc */
         u32 *last_vblank;               /* protected by dev->vbl_lock, used */
@@ -1284,11 +1363,22 @@ extern int drm_wait_vblank(struct drm_device *dev, void *data,
                            struct drm_file *filp);
 extern int drm_vblank_wait(struct drm_device *dev, unsigned int *vbl_seq);
 extern u32 drm_vblank_count(struct drm_device *dev, int crtc);
+extern u32 drm_vblank_count_and_time(struct drm_device *dev, int crtc,
+                                     struct timeval *vblanktime);
 extern void drm_handle_vblank(struct drm_device *dev, int crtc);
 extern int drm_vblank_get(struct drm_device *dev, int crtc);
 extern void drm_vblank_put(struct drm_device *dev, int crtc);
 extern void drm_vblank_off(struct drm_device *dev, int crtc);
 extern void drm_vblank_cleanup(struct drm_device *dev);
+extern u32 drm_get_last_vbltimestamp(struct drm_device *dev, int crtc,
+                                     struct timeval *tvblank, unsigned flags);
+extern 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);
+extern void drm_calc_timestamping_constants(struct drm_crtc *crtc);
+
 /* Modesetting support */
 extern void drm_vblank_pre_modeset(struct drm_device *dev, int crtc);
 extern void drm_vblank_post_modeset(struct drm_device *dev, int crtc);
@@ -1340,6 +1430,9 @@ extern void drm_put_dev(struct drm_device *dev);
 extern int drm_put_minor(struct drm_minor **minor);
 extern unsigned int drm_debug;
 
+extern unsigned int drm_vblank_offdelay;
+extern unsigned int drm_timestamp_precision;
+
 extern struct class *drm_class;
 extern struct proc_dir_entry *drm_proc_root;
 extern struct dentry *drm_debugfs_root;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 029aa688e787..acd7fade160d 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -351,8 +351,14 @@ struct drm_crtc {
 
         bool enabled;
 
+        /* Requested mode from modesetting. */
         struct drm_display_mode mode;
 
+        /* Programmed mode in hw, after adjustments for encoders,
+         * crtc, panel scaling etc. Needed for timestamping etc.
+         */
+        struct drm_display_mode hwmode;
+
         int x, y;
         const struct drm_crtc_funcs *funcs;
 
@@ -360,6 +366,9 @@ struct drm_crtc {
         uint32_t gamma_size;
         uint16_t *gamma_store;
 
+        /* Constants needed for precise vblank and swap timestamping. */
+        s64 framedur_ns, linedur_ns, pixeldur_ns;
+
         /* if you are using the helper */
         void *helper_private;
 };