FreeBSD/Linux Kernel Cross Reference
sys/dev/drm2/drm_irq.c

     /**
      * \file drm_irq.c
      * IRQ support
      *
      * \author Rickard E. (Rik) Faith <faith@valinux.com>
      * \author Gareth Hughes <gareth@valinux.com>
      */
     
     /*
     * Created: Fri Mar 19 14:30:16 1999 by faith@valinux.com
     *
     * Copyright 1999, 2000 Precision Insight, Inc., Cedar Park, Texas.
     * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
     * All Rights Reserved.
     *
     * Permission is hereby granted, free of charge, to any person obtaining a
     * copy of this software and associated documentation files (the "Software"),
     * to deal in the Software without restriction, including without limitation
     * the rights to use, copy, modify, merge, publish, distribute, sublicense,
     * and/or sell copies of the Software, and to permit persons to whom the
     * Software is furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice (including the next
     * paragraph) shall be included in all copies or substantial portions of the
     * Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
     * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
     * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     * OTHER DEALINGS IN THE SOFTWARE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <dev/drm2/drmP.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.
     *
     * \param inode device inode.
     * \param file_priv DRM file private.
     * \param cmd command.
     * \param arg user argument, pointing to a drm_irq_busid structure.
     * \return zero on success or a negative number on failure.
     *
     * Finds the PCI device with the specified bus id and gets its IRQ number.
     * This IOCTL is deprecated, and will now return EINVAL for any busid not equal
     * to that of the device that this DRM instance attached to.
     */
    int drm_irq_by_busid(struct drm_device *dev, void *data,
                         struct drm_file *file_priv)
    {
            struct drm_irq_busid *p = data;
    
            if (!dev->driver->bus->irq_by_busid)
                    return -EINVAL;
    
            if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
                    return -EINVAL;
    
            return dev->driver->bus->irq_by_busid(dev, p);
    }
    
    /*
     * 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)
    {
           u32 vblcount;
           s64 diff_ns;
           int vblrc;
           struct timeval tvblank;
           int count = DRM_TIMESTAMP_MAXRETRIES;
   
           /* 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.
            */
           mtx_lock(&dev->vblank_time_lock);
   
           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) && (--count) && vblrc);
   
           if (!count)
                   vblrc = 0;
   
           /* 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) && (abs64(diff_ns) > 1000000)) {
                   atomic_inc(&dev->_vblank_count[crtc]);
                   smp_mb__after_atomic_inc();
           }
   
           /* Invalidate all timestamps while vblank irq's are off. */
           clear_vblank_timestamps(dev, crtc);
   
           mtx_unlock(&dev->vblank_time_lock);
   }
   
   static void vblank_disable_fn(void *arg)
   {
           struct drm_device *dev = (struct drm_device *)arg;
           int i;
   
           if (!dev->vblank_disable_allowed)
                   return;
   
           for (i = 0; i < dev->num_crtcs; i++) {
                   mtx_lock(&dev->vbl_lock);
                   if (atomic_read(&dev->vblank_refcount[i]) == 0 &&
                       dev->vblank_enabled[i]) {
                           DRM_DEBUG("disabling vblank on crtc %d\n", i);
                           vblank_disable_and_save(dev, i);
                   }
                   mtx_unlock(&dev->vbl_lock);
           }
   }
   
   void drm_vblank_cleanup(struct drm_device *dev)
   {
           /* Bail if the driver didn't call drm_vblank_init() */
           if (dev->num_crtcs == 0)
                   return;
   
           callout_stop(&dev->vblank_disable_callout);
   
           vblank_disable_fn(dev);
   
           free(dev->_vblank_count, DRM_MEM_VBLANK);
           free(dev->vblank_refcount, DRM_MEM_VBLANK);
           free(dev->vblank_enabled, DRM_MEM_VBLANK);
           free(dev->last_vblank, DRM_MEM_VBLANK);
           free(dev->last_vblank_wait, DRM_MEM_VBLANK);
           free(dev->vblank_inmodeset, DRM_MEM_VBLANK);
           free(dev->_vblank_time, DRM_MEM_VBLANK);
   
           mtx_destroy(&dev->vbl_lock);
           mtx_destroy(&dev->vblank_time_lock);
   
           dev->num_crtcs = 0;
   }
   EXPORT_SYMBOL(drm_vblank_cleanup);
   
   int drm_vblank_init(struct drm_device *dev, int num_crtcs)
   {
           int i, ret = -ENOMEM;
   
           callout_init(&dev->vblank_disable_callout, 1);
           mtx_init(&dev->vbl_lock, "drmvbl", NULL, MTX_DEF);
           mtx_init(&dev->vblank_time_lock, "drmvtl", NULL, MTX_DEF);
   
           dev->num_crtcs = num_crtcs;
   
           dev->_vblank_count = malloc(sizeof(atomic_t) * num_crtcs,
               DRM_MEM_VBLANK, M_NOWAIT);
           if (!dev->_vblank_count)
                   goto err;
   
           dev->vblank_refcount = malloc(sizeof(atomic_t) * num_crtcs,
               DRM_MEM_VBLANK, M_NOWAIT);
           if (!dev->vblank_refcount)
                   goto err;
   
           dev->vblank_enabled = malloc(num_crtcs * sizeof(int),
               DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
           if (!dev->vblank_enabled)
                   goto err;
   
           dev->last_vblank = malloc(num_crtcs * sizeof(u32),
               DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
           if (!dev->last_vblank)
                   goto err;
   
           dev->last_vblank_wait = malloc(num_crtcs * sizeof(u32),
               DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
           if (!dev->last_vblank_wait)
                   goto err;
   
           dev->vblank_inmodeset = malloc(num_crtcs * sizeof(int),
               DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
           if (!dev->vblank_inmodeset)
                   goto err;
   
           dev->_vblank_time = malloc(num_crtcs * DRM_VBLANKTIME_RBSIZE *
               sizeof(struct timeval), DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
           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++) {
                   atomic_set(&dev->_vblank_count[i], 0);
                   atomic_set(&dev->vblank_refcount[i], 0);
           }
   
           dev->vblank_disable_allowed = 0;
           return 0;
   
   err:
           drm_vblank_cleanup(dev);
           return ret;
   }
   EXPORT_SYMBOL(drm_vblank_init);
   
   /**
    * Install IRQ handler.
    *
    * \param dev DRM device.
    *
    * Initializes the IRQ related data. Installs the handler, calling the driver
    * \c irq_preinstall() and \c irq_postinstall() functions
    * before and after the installation.
    */
   int drm_irq_install(struct drm_device *dev)
   {
           int ret;
           unsigned long sh_flags = 0;
   
           if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
                   return -EINVAL;
   
           if (drm_dev_to_irq(dev) == 0)
                   return -EINVAL;
   
           DRM_LOCK(dev);
   
           /* Driver must have been initialized */
           if (!dev->dev_private) {
                   DRM_UNLOCK(dev);
                   return -EINVAL;
           }
   
           if (dev->irq_enabled) {
                   DRM_UNLOCK(dev);
                   return -EBUSY;
           }
           dev->irq_enabled = 1;
           DRM_UNLOCK(dev);
   
           DRM_DEBUG("irq=%d\n", drm_dev_to_irq(dev));
   
           /* Before installing handler */
           if (dev->driver->irq_preinstall)
                   dev->driver->irq_preinstall(dev);
   
           /* Install handler */
           sh_flags = INTR_TYPE_TTY | INTR_MPSAFE;
           if (!drm_core_check_feature(dev, DRIVER_IRQ_SHARED))
                   /*
                    * FIXME Linux<->FreeBSD: This seems to make
                    * bus_setup_intr() unhappy: it was reported to return
                    * EINVAL on an i915 board (8086:2592 in a Thinkpad
                    * X41).
                    *
                    * For now, no driver we have use that.
                    */
                   sh_flags |= INTR_EXCL;
   
           ret = -bus_setup_intr(dev->dev, dev->irqr, sh_flags, NULL,
               dev->driver->irq_handler, dev, &dev->irqh);
   
           if (ret < 0) {
                   device_printf(dev->dev, "Error setting interrupt: %d\n", -ret);
                   DRM_LOCK(dev);
                   dev->irq_enabled = 0;
                   DRM_UNLOCK(dev);
                   return ret;
           }
   
           /* After installing handler */
           if (dev->driver->irq_postinstall)
                   ret = dev->driver->irq_postinstall(dev);
   
           if (ret < 0) {
                   DRM_LOCK(dev);
                   dev->irq_enabled = 0;
                   DRM_UNLOCK(dev);
                   bus_teardown_intr(dev->dev, dev->irqr, dev->irqh);
                   dev->driver->bus->free_irq(dev);
           }
   
           return ret;
   }
   EXPORT_SYMBOL(drm_irq_install);
   
   /**
    * Uninstall the IRQ handler.
    *
    * \param dev DRM device.
    *
    * Calls the driver's \c irq_uninstall() function, and stops the irq.
    */
   int drm_irq_uninstall(struct drm_device *dev)
   {
           int irq_enabled, i;
   
           if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
                   return -EINVAL;
   
           DRM_LOCK(dev);
           irq_enabled = dev->irq_enabled;
           dev->irq_enabled = 0;
           DRM_UNLOCK(dev);
   
           /*
            * Wake up any waiters so they don't hang.
            */
           if (dev->num_crtcs) {
                   mtx_lock(&dev->vbl_lock);
                   for (i = 0; i < dev->num_crtcs; i++) {
                           DRM_WAKEUP(&dev->_vblank_count[i]);
                           dev->vblank_enabled[i] = 0;
                           dev->last_vblank[i] =
                                   dev->driver->get_vblank_counter(dev, i);
                   }
                   mtx_unlock(&dev->vbl_lock);
           }
   
           if (!irq_enabled)
                   return -EINVAL;
   
           DRM_DEBUG("irq=%d\n", drm_dev_to_irq(dev));
   
           if (dev->driver->irq_uninstall)
                   dev->driver->irq_uninstall(dev);
   
           bus_teardown_intr(dev->dev, dev->irqr, dev->irqh);
           dev->driver->bus->free_irq(dev);
   
           return 0;
   }
   EXPORT_SYMBOL(drm_irq_uninstall);
   
   /**
    * IRQ control ioctl.
    *
    * \param inode device inode.
    * \param file_priv DRM file private.
    * \param cmd command.
    * \param arg user argument, pointing to a drm_control structure.
    * \return zero on success or a negative number on failure.
    *
    * Calls irq_install() or irq_uninstall() according to \p arg.
    */
   int drm_control(struct drm_device *dev, void *data,
                   struct drm_file *file_priv)
   {
           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
            */
   
   
           switch (ctl->func) {
           case DRM_INST_HANDLER:
                   if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
                           return 0;
                   if (drm_core_check_feature(dev, DRIVER_MODESET))
                           return 0;
                   if (dev->if_version < DRM_IF_VERSION(1, 2) &&
                       ctl->irq != drm_dev_to_irq(dev))
                           return -EINVAL;
                   return drm_irq_install(dev);
           case DRM_UNINST_HANDLER:
                   if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
                           return 0;
                   if (drm_core_check_feature(dev, DRIVER_MODESET))
                           return 0;
                   return drm_irq_uninstall(dev);
           default:
                   return -EINVAL;
           }
   }
   
   /**
    * 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;
   
           /* Fields of interlaced scanout modes are only halve a frame duration.
            * Double the dotclock to get halve the frame-/line-/pixelduration.
            */
           if (crtc->hwmode.flags & DRM_MODE_FLAG_INTERLACE)
                   dotclock *= 2;
   
           /* 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;
           }
   
           /* 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.
                    */
                   critical_enter();
   
                   /* Get system timestamp before query. */
                   getmicrouptime(&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. */
                   getmicrouptime(&raw_time);
   #ifdef FREEBSD_NOTYET
                   if (!drm_timestamp_monotonic)
                           mono_time_offset = ktime_get_monotonic_offset();
   #endif /* FREEBSD_NOTYET */
   
                   critical_exit();
   
                   /* 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;
           }
   
   #ifdef FREEBSD_NOTYET
           if (!drm_timestamp_monotonic)
                   etime = ktime_sub(etime, mono_time_offset);
   
           /* save this only for debugging purposes */
           tv_etime = ktime_to_timeval(etime);
   #endif /* FREEBSD_NOTYET */
           /* 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)@ %jd.%jd -> %jd.%jd [e %d us, %d rep]\n",
                     crtc, (int)vbl_status, hpos, vpos, (uintmax_t)raw_time.tv_sec,
                     (uintmax_t)raw_time.tv_usec, (uintmax_t)vblank_time->tv_sec,
                     (uintmax_t)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);
   
   static struct timeval get_drm_timestamp(void)
   {
           struct timeval now;
   
           microtime(&now);
   #ifdef FREEBSD_NOTYET
           if (!drm_timestamp_monotonic)
                   now = ktime_sub(now, ktime_get_monotonic_offset());
   #endif /* defined(FREEBSD_NOTYET) */
   
           return now;
   }
   
   /**
    * 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;
   
           /* 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 current monotonic/gettimeofday timestamp as best estimate.
            */
           *tvblank = get_drm_timestamp();
   
           return 0;
   }
   EXPORT_SYMBOL(drm_get_last_vbltimestamp);
   
   /**
    * drm_vblank_count - retrieve "cooked" vblank counter value
    * @dev: DRM device
    * @crtc: which counter to retrieve
    *
    * 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.
    */
   u32 drm_vblank_count(struct drm_device *dev, int crtc)
   {
           return atomic_read(&dev->_vblank_count[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);
   
   static void send_vblank_event(struct drm_device *dev,
                   struct drm_pending_vblank_event *e,
                   unsigned long seq, struct timeval *now)
   {
           WARN_ON_SMP(!mtx_owned(&dev->event_lock));
           e->event.sequence = seq;
           e->event.tv_sec = now->tv_sec;
           e->event.tv_usec = now->tv_usec;
   
           list_add_tail(&e->base.link,
                         &e->base.file_priv->event_list);
           drm_event_wakeup(&e->base);
           CTR3(KTR_DRM, "vblank_event_delivered %d %d %d",
               e->base.pid, e->pipe, e->event.sequence);
   }
   
   /**
    * drm_send_vblank_event - helper to send vblank event after pageflip
    * @dev: DRM device
    * @crtc: CRTC in question
    * @e: the event to send
    *
    * Updates sequence # and timestamp on event, and sends it to userspace.
    * Caller must hold event lock.
    */
   void drm_send_vblank_event(struct drm_device *dev, int crtc,
                   struct drm_pending_vblank_event *e)
   {
           struct timeval now;
           unsigned int seq;
           if (crtc >= 0) {
                   seq = drm_vblank_count_and_time(dev, crtc, &now);
           } else {
                   seq = 0;
   
                   now = get_drm_timestamp();
           }
           send_vblank_event(dev, e, seq, &now);
   }
   EXPORT_SYMBOL(drm_send_vblank_event);
   
   /**
    * drm_update_vblank_count - update the master vblank counter
    * @dev: DRM device
    * @crtc: counter to update
    *
    * Call back into the driver to update the appropriate vblank counter
    * (specified by @crtc).  Deal with wraparound, if it occurred, and
    * update the last read value so we can deal with wraparound on the next
    * call if necessary.
    *
    * Only necessary when going from off->on, to account for frames we
    * didn't get an interrupt for.
    *
    * Note: caller must hold dev->vbl_lock since this reads & writes
    * device vblank fields.
    */
   static void drm_update_vblank_count(struct drm_device *dev, int crtc)
   {
           u32 cur_vblank, diff, tslot, rc;
           struct timeval t_vblank;
   
           /*
            * Interrupts were disabled prior to this call, so deal with counter
            * wrap if needed.
            * 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.
            */
           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;
   
                   DRM_DEBUG("last_vblank[%d]=0x%x, cur_vblank=0x%x => diff=0x%x\n",
                             crtc, dev->last_vblank[crtc], cur_vblank, diff);
           }
   
           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_mb__before_atomic_inc();
           atomic_add(diff, &dev->_vblank_count[crtc]);
           smp_mb__after_atomic_inc();
   }
   
   /**
    * drm_vblank_get - get a reference count on vblank events
    * @dev: DRM device
    * @crtc: which CRTC to own
    *
    * Acquire a reference count on vblank events to avoid having them disabled
    * while in use.
    *
    * RETURNS
    * Zero on success, nonzero on failure.
    */
   int drm_vblank_get(struct drm_device *dev, int crtc)
   {
           int ret = 0;
   
           mtx_lock(&dev->vbl_lock);
           /* Going from 0->1 means we have to enable interrupts again */
           if (atomic_add_return(1, &dev->vblank_refcount[crtc]) == 1) {
                   mtx_lock(&dev->vblank_time_lock);
                   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);
                           if (ret)
                                   atomic_dec(&dev->vblank_refcount[crtc]);
                           else {
                                   dev->vblank_enabled[crtc] = 1;
                                   drm_update_vblank_count(dev, crtc);
                           }
                   }
                   mtx_unlock(&dev->vblank_time_lock);
           } else {
                   if (!dev->vblank_enabled[crtc]) {
                           atomic_dec(&dev->vblank_refcount[crtc]);
                           ret = -EINVAL;
                   }
           }
           mtx_unlock(&dev->vbl_lock);
   
           return ret;
   }
   EXPORT_SYMBOL(drm_vblank_get);
   
   /**
    * drm_vblank_put - give up ownership of vblank events
    * @dev: DRM device
    * @crtc: which counter to give up
    *
    * Release ownership of a given vblank counter, turning off interrupts
    * 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);
   
           /* Last user schedules interrupt disable */
           if (atomic_dec_and_test(&dev->vblank_refcount[crtc]) &&
               (drm_vblank_offdelay > 0))
                   callout_reset(&dev->vblank_disable_callout,
                       (drm_vblank_offdelay * DRM_HZ) / 1000,
                       vblank_disable_fn, dev);
   }
   EXPORT_SYMBOL(drm_vblank_put);
   
   /**
    * drm_vblank_off - disable vblank events on a CRTC
    * @dev: DRM device
    * @crtc: CRTC in question
    *
    * Caller must hold event lock.
    */
   void drm_vblank_off(struct drm_device *dev, int crtc)
   {
           struct drm_pending_vblank_event *e, *t;
           struct timeval now;
           unsigned int seq;
   
           mtx_lock(&dev->vbl_lock);
           vblank_disable_and_save(dev, crtc);
           DRM_WAKEUP(&dev->_vblank_count[crtc]);
   
           /* Send any queued vblank events, lest the natives grow disquiet */
           seq = drm_vblank_count_and_time(dev, crtc, &now);
   
           mtx_lock(&dev->event_lock);
           list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
                   if (e->pipe != crtc)
                           continue;
                   DRM_DEBUG("Sending premature vblank event on disable: \
                            wanted %d, current %d\n",
                            e->event.sequence, seq);
                  list_del(&e->base.link);
                  drm_vblank_put(dev, e->pipe);
                  send_vblank_event(dev, e, seq, &now);
          }
          mtx_unlock(&dev->event_lock);
  
          mtx_unlock(&dev->vbl_lock);
  }
  EXPORT_SYMBOL(drm_vblank_off);
  
  /**
   * drm_vblank_pre_modeset - account for vblanks across mode sets
   * @dev: DRM device
   * @crtc: CRTC in question
   *
   * Account for vblank events across mode setting events, which will likely
   * reset the hardware frame counter.
   */
  void drm_vblank_pre_modeset(struct drm_device *dev, int crtc)
  {
          /* vblank is not initialized (IRQ not installed ?), or has been freed */
          if (!dev->num_crtcs)
                  return;
          /*
           * To avoid all the problems that might happen if interrupts
           * were enabled/disabled around or between these calls, we just
           * have the kernel take a reference on the CRTC (just once though
           * to avoid corrupting the count if multiple, mismatch calls occur),
           * so that interrupts remain enabled in the interim.
           */
          if (!dev->vblank_inmodeset[crtc]) {
                  dev->vblank_inmodeset[crtc] = 0x1;
                  if (drm_vblank_get(dev, crtc) == 0)
                          dev->vblank_inmodeset[crtc] |= 0x2;
          }
  }
  EXPORT_SYMBOL(drm_vblank_pre_modeset);
  
  void drm_vblank_post_modeset(struct drm_device *dev, int crtc)
  {
          /* vblank is not initialized (IRQ not installed ?), or has been freed */
          if (!dev->num_crtcs)
                  return;
  
          if (dev->vblank_inmodeset[crtc]) {
                  mtx_lock(&dev->vbl_lock);
                  dev->vblank_disable_allowed = 1;
                  mtx_unlock(&dev->vbl_lock);
  
                  if (dev->vblank_inmodeset[crtc] & 0x2)
                          drm_vblank_put(dev, crtc);
  
                  dev->vblank_inmodeset[crtc] = 0;
          }
  }
  EXPORT_SYMBOL(drm_vblank_post_modeset);
  
  /**
   * drm_modeset_ctl - handle vblank event counter changes across mode switch
   * @DRM_IOCTL_ARGS: standard ioctl arguments
   *
   * Applications should call the %_DRM_PRE_MODESET and %_DRM_POST_MODESET
   * ioctls around modesetting so that any lost vblank events are accounted for.
   *
   * Generally the counter will reset across mode sets.  If interrupts are
   * enabled around this call, we don't have to do anything since the counter
   * will have already been incremented.
   */
  int drm_modeset_ctl(struct drm_device *dev, void *data,
                      struct drm_file *file_priv)
  {
          struct drm_modeset_ctl *modeset = data;
          unsigned int crtc;
  
          /* If drm_vblank_init() hasn't been called yet, just no-op */
          if (!dev->num_crtcs)
                  return 0;
  
          /* KMS drivers handle this internally */
          if (drm_core_check_feature(dev, DRIVER_MODESET))
                  return 0;
  
          crtc = modeset->crtc;
          if (crtc >= dev->num_crtcs)
                  return -EINVAL;
  
          switch (modeset->cmd) {
          case _DRM_PRE_MODESET:
                  drm_vblank_pre_modeset(dev, crtc);
                  break;
          case _DRM_POST_MODESET:
                  drm_vblank_post_modeset(dev, crtc);
                  break;
          default:
                  return -EINVAL;
          }
  
          return 0;
  }
  
  static void
  drm_vblank_event_destroy(struct drm_pending_event *e)
  {
  
          free(e, DRM_MEM_VBLANK);
  }
  
  static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
                                    union drm_wait_vblank *vblwait,
                                    struct drm_file *file_priv)
  {
          struct drm_pending_vblank_event *e;
          struct timeval now;
          unsigned int seq;
          int ret;
  
          e = malloc(sizeof *e, DRM_MEM_VBLANK, M_NOWAIT | M_ZERO);
          if (e == NULL) {
                  ret = -ENOMEM;
                  goto err_put;
          }
  
          e->pipe = pipe;
          e->base.pid = curproc->p_pid;
          e->event.base.type = DRM_EVENT_VBLANK;
          e->event.base.length = sizeof e->event;
          e->event.user_data = vblwait->request.signal;
          e->base.event = &e->event.base;
          e->base.file_priv = file_priv;
          e->base.destroy = drm_vblank_event_destroy;
  
          mtx_lock(&dev->event_lock);
  
          if (file_priv->event_space < sizeof e->event) {
                  ret = -EBUSY;
                  goto err_unlock;
          }
  
          file_priv->event_space -= sizeof e->event;
          seq = drm_vblank_count_and_time(dev, pipe, &now);
  
          if ((vblwait->request.type & _DRM_VBLANK_NEXTONMISS) &&
              (seq - vblwait->request.sequence) <= (1 << 23)) {
                  vblwait->request.sequence = seq + 1;
                  vblwait->reply.sequence = vblwait->request.sequence;
          }
  
          DRM_DEBUG("event on vblank count %d, current %d, crtc %d\n",
                    vblwait->request.sequence, seq, pipe);
  
          CTR4(KTR_DRM, "vblank_event_queued %d %d rt %x %d", curproc->p_pid, pipe,
              vblwait->request.type, vblwait->request.sequence);
  
          e->event.sequence = vblwait->request.sequence;
          if ((seq - vblwait->request.sequence) <= (1 << 23)) {
                  drm_vblank_put(dev, pipe);
                  send_vblank_event(dev, e, seq, &now);
                  vblwait->reply.sequence = seq;
          } else {
                  /* drm_handle_vblank_events will call drm_vblank_put */
                  list_add_tail(&e->base.link, &dev->vblank_event_list);
                  vblwait->reply.sequence = vblwait->request.sequence;
          }
  
          mtx_unlock(&dev->event_lock);
  
          return 0;
  
  err_unlock:
          mtx_unlock(&dev->event_lock);
          free(e, DRM_MEM_VBLANK);
  err_put:
          drm_vblank_put(dev, pipe);
          return ret;
  }
  
  /**
   * Wait for VBLANK.
   *
   * \param inode device inode.
   * \param file_priv DRM file private.
   * \param cmd command.
   * \param data user argument, pointing to a drm_wait_vblank structure.
   * \return zero on success or a negative number on failure.
   *
   * This function enables the vblank interrupt on the pipe requested, then
   * sleeps waiting for the requested sequence number to occur, and drops
   * the vblank interrupt refcount afterwards. (vblank irq disable follows that
   * after a timeout with no further vblank waits scheduled).
   */
  int drm_wait_vblank(struct drm_device *dev, void *data,
                      struct drm_file *file_priv)
  {
          union drm_wait_vblank *vblwait = data;
          int ret;
          unsigned int flags, seq, crtc, high_crtc;
  
          if (/*(!drm_dev_to_irq(dev)) || */(!dev->irq_enabled))
                  return -EINVAL;
  
          if (vblwait->request.type & _DRM_VBLANK_SIGNAL)
                  return -EINVAL;
  
          if (vblwait->request.type &
              ~(_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK |
                _DRM_VBLANK_HIGH_CRTC_MASK)) {
                  DRM_ERROR("Unsupported type value 0x%x, supported mask 0x%x\n",
                            vblwait->request.type,
                            (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK |
                             _DRM_VBLANK_HIGH_CRTC_MASK));
                  return -EINVAL;
          }
  
          flags = vblwait->request.type & _DRM_VBLANK_FLAGS_MASK;
          high_crtc = (vblwait->request.type & _DRM_VBLANK_HIGH_CRTC_MASK);
          if (high_crtc)
                  crtc = high_crtc >> _DRM_VBLANK_HIGH_CRTC_SHIFT;
          else
                  crtc = flags & _DRM_VBLANK_SECONDARY ? 1 : 0;
          if (crtc >= dev->num_crtcs)
                  return -EINVAL;
  
          ret = drm_vblank_get(dev, crtc);
          if (ret) {
                  DRM_DEBUG("failed to acquire vblank counter, %d\n", ret);
                  return ret;
          }
          seq = drm_vblank_count(dev, crtc);
  
          switch (vblwait->request.type & _DRM_VBLANK_TYPES_MASK) {
          case _DRM_VBLANK_RELATIVE:
                  vblwait->request.sequence += seq;
                  vblwait->request.type &= ~_DRM_VBLANK_RELATIVE;
          case _DRM_VBLANK_ABSOLUTE:
                  break;
          default:
                  ret = -EINVAL;
                  goto done;
          }
  
          if (flags & _DRM_VBLANK_EVENT) {
                  /* must hold on to the vblank ref until the event fires
                   * drm_vblank_put will be called asynchronously
                   */
                  return drm_queue_vblank_event(dev, crtc, vblwait, file_priv);
          }
  
          if ((flags & _DRM_VBLANK_NEXTONMISS) &&
              (seq - vblwait->request.sequence) <= (1<<23)) {
                  vblwait->request.sequence = seq + 1;
          }
  
          DRM_DEBUG("waiting on vblank count %d, crtc %d\n",
                    vblwait->request.sequence, crtc);
          dev->last_vblank_wait[crtc] = vblwait->request.sequence;
          mtx_lock(&dev->vblank_time_lock);
          while (((drm_vblank_count(dev, crtc) - vblwait->request.sequence) >
              (1 << 23)) && dev->irq_enabled) {
                  /*
                   * The wakeups from the drm_irq_uninstall() and
                   * drm_vblank_off() may be lost there since vbl_lock
                   * is not held.  Then, the timeout will wake us; the 3
                   * seconds delay should not be a problem for
                   * application when crtc is disabled or irq
                   * uninstalled anyway.
                   */
                  ret = -msleep(&dev->_vblank_count[crtc], &dev->vblank_time_lock,
                      PCATCH, "drmvbl", 3 * hz);
                  if (ret == -ERESTART)
                          ret = -ERESTARTSYS;
                  if (ret != 0)
                          break;
          }
          mtx_unlock(&dev->vblank_time_lock);
          if (ret != -EINTR) {
                  struct timeval now;
                  long reply_seq;
  
                  reply_seq = drm_vblank_count_and_time(dev, crtc, &now);
                  CTR5(KTR_DRM, "wait_vblank %d %d rt %x success %d %d",
                      curproc->p_pid, crtc, vblwait->request.type,
                      vblwait->request.sequence, reply_seq);
  
                  vblwait->reply.sequence = reply_seq;
                  vblwait->reply.tval_sec = now.tv_sec;
                  vblwait->reply.tval_usec = now.tv_usec;
  
                  DRM_DEBUG("returning %d to client\n",
                            vblwait->reply.sequence);
          } else {
                  CTR5(KTR_DRM, "wait_vblank %d %d rt %x error %d %d",
                      curproc->p_pid, crtc, vblwait->request.type, ret,
                      vblwait->request.sequence);
  
                  DRM_DEBUG("vblank wait interrupted by signal\n");
          }
  
  done:
          drm_vblank_put(dev, crtc);
          return ret;
  }
  
  static void drm_handle_vblank_events(struct drm_device *dev, int crtc)
  {
          struct drm_pending_vblank_event *e, *t;
          struct timeval now;
          unsigned int seq;
  
          seq = drm_vblank_count_and_time(dev, crtc, &now);
  
          mtx_lock(&dev->event_lock);
  
          list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
                  if (e->pipe != crtc)
                          continue;
                  if ((seq - e->event.sequence) > (1<<23))
                          continue;
  
                  DRM_DEBUG("vblank event on %d, current %d\n",
                            e->event.sequence, seq);
  
                  list_del(&e->base.link);
                  drm_vblank_put(dev, e->pipe);
                  send_vblank_event(dev, e, seq, &now);
          }
  
          mtx_unlock(&dev->event_lock);
  
          CTR2(KTR_DRM, "drm_handle_vblank_events %d %d", seq, crtc);
  }
  
  /**
   * drm_handle_vblank - handle a vblank event
   * @dev: DRM device
   * @crtc: where this event occurred
   *
   * Drivers should call this routine in their vblank interrupt handlers to
   * update the vblank counter and send any signals that may be pending.
   */
  bool drm_handle_vblank(struct drm_device *dev, int crtc)
  {
          u32 vblcount;
          s64 diff_ns;
          struct timeval tvblank;
  
          if (!dev->num_crtcs)
                  return false;
  
          /* Need timestamp lock to prevent concurrent execution with
           * vblank enable/disable, as this would cause inconsistent
           * or corrupted timestamps and vblank counts.
           */
          mtx_lock(&dev->vblank_time_lock);
  
          /* Vblank irq handling disabled. Nothing to do. */
          if (!dev->vblank_enabled[crtc]) {
                  mtx_unlock(&dev->vblank_time_lock);
                  return false;
          }
  
          /* 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 (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) {
                  /* Store new timestamp in ringbuffer. */
                  vblanktimestamp(dev, crtc, vblcount + 1) = tvblank;
  
                  /* Increment cooked vblank count. This also atomically commits
                   * the timestamp computed above.
                   */
                  smp_mb__before_atomic_inc();
                  atomic_inc(&dev->_vblank_count[crtc]);
                  smp_mb__after_atomic_inc();
          } else {
                  DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n",
                            crtc, (int) diff_ns);
          }
  
          DRM_WAKEUP(&dev->_vblank_count[crtc]);
          drm_handle_vblank_events(dev, crtc);
  
          mtx_unlock(&dev->vblank_time_lock);
          return true;
  }
  EXPORT_SYMBOL(drm_handle_vblank);

Cache object: 7d6889c950f659a27c38bcf158391218