text: /**
   * \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 "drmP.h"
  #include "drm_trace.h"
  
  #include <linux/interrupt.h>	/* For task queue support */
  #include <linux/slab.h>
  
  #include <linux/vgaarb.h>
  #include <linux/export.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)
  {
  	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.
  	 */
  	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) && (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);
  
  	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
  }
  
  static void vblank_disable_fn(unsigned long arg)
  {
  	struct drm_device *dev = (struct drm_device *)arg;
  	unsigned long irqflags;
  	int i;
  
  	if (!dev->vblank_disable_allowed)
  		return;
  
  	for (i = 0; i < dev->num_crtcs; i++) {
  		spin_lock_irqsave(&dev->vbl_lock, irqflags);
  		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);
  		}
  		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
  	}
  }
  
  void drm_vblank_cleanup(struct drm_device *dev)
  {
  	/* Bail if the driver didn't call drm_vblank_init() */
  	if (dev->num_crtcs == 0)
  		return;
  
  	del_timer(&dev->vblank_disable_timer);
  
  	vblank_disable_fn((unsigned long)dev);
  
  	kfree(dev->vbl_queue);
  	kfree(dev->_vblank_count);
  	kfree(dev->vblank_refcount);
  	kfree(dev->vblank_enabled);
  	kfree(dev->last_vblank);
  	kfree(dev->last_vblank_wait);
  	kfree(dev->vblank_inmodeset);
  	kfree(dev->_vblank_time);
  
  	dev->num_crtcs = 0;
  }
  EXPORT_SYMBOL(drm_vblank_cleanup);
  
  int drm_vblank_init(struct drm_device *dev, int num_crtcs)
  {
  	int i, ret = -ENOMEM;
  
  	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,
  				 GFP_KERNEL);
  	if (!dev->vbl_queue)
  		goto err;
  
  	dev->_vblank_count = kmalloc(sizeof(atomic_t) * num_crtcs, GFP_KERNEL);
  	if (!dev->_vblank_count)
  		goto err;
  
  	dev->vblank_refcount = kmalloc(sizeof(atomic_t) * num_crtcs,
  				       GFP_KERNEL);
  	if (!dev->vblank_refcount)
  		goto err;
  
  	dev->vblank_enabled = kcalloc(num_crtcs, sizeof(int), GFP_KERNEL);
  	if (!dev->vblank_enabled)
  		goto err;
  
  	dev->last_vblank = kcalloc(num_crtcs, sizeof(u32), GFP_KERNEL);
  	if (!dev->last_vblank)
  		goto err;
  
  	dev->last_vblank_wait = kcalloc(num_crtcs, sizeof(u32), GFP_KERNEL);
  	if (!dev->last_vblank_wait)
  		goto err;
  
  	dev->vblank_inmodeset = kcalloc(num_crtcs, sizeof(int), GFP_KERNEL);
  	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]);
  		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);
  
  static void drm_irq_vgaarb_nokms(void *cookie, bool state)
  {
  	struct drm_device *dev = cookie;
  
  	if (dev->driver->vgaarb_irq) {
  		dev->driver->vgaarb_irq(dev, state);
  		return;
  	}
  
  	if (!dev->irq_enabled)
  		return;
  
  	if (state) {
  		if (dev->driver->irq_uninstall)
  			dev->driver->irq_uninstall(dev);
  	} else {
  		if (dev->driver->irq_preinstall)
  			dev->driver->irq_preinstall(dev);
  		if (dev->driver->irq_postinstall)
  			dev->driver->irq_postinstall(dev);
  	}
  }
  
  /**
   * Install IRQ handler.
   *
   * \param dev DRM device.
   *
   * Initializes the IRQ related data. Installs the handler, calling the driver
   * \c drm_driver_irq_preinstall() and \c drm_driver_irq_postinstall() functions
   * before and after the installation.
   */
  int drm_irq_install(struct drm_device *dev)
  {
  	int ret = 0;
  	unsigned long sh_flags = 0;
  	char *irqname;
  
  	if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
  		return -EINVAL;
  
  	if (drm_dev_to_irq(dev) == 0)
  		return -EINVAL;
  
  	mutex_lock(&dev->struct_mutex);
  
  	/* Driver must have been initialized */
  	if (!dev->dev_private) {
  		mutex_unlock(&dev->struct_mutex);
  		return -EINVAL;
  	}
  
  	if (dev->irq_enabled) {
  		mutex_unlock(&dev->struct_mutex);
  		return -EBUSY;
  	}
  	dev->irq_enabled = 1;
  	mutex_unlock(&dev->struct_mutex);
  
  	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 */
  	if (drm_core_check_feature(dev, DRIVER_IRQ_SHARED))
  		sh_flags = IRQF_SHARED;
  
  	if (dev->devname)
  		irqname = dev->devname;
  	else
  		irqname = dev->driver->name;
  
  	ret = request_irq(drm_dev_to_irq(dev), dev->driver->irq_handler,
  			  sh_flags, irqname, dev);
  
  	if (ret < 0) {
  		mutex_lock(&dev->struct_mutex);
  		dev->irq_enabled = 0;
  		mutex_unlock(&dev->struct_mutex);
  		return ret;
  	}
  
  	if (!drm_core_check_feature(dev, DRIVER_MODESET))
  		vga_client_register(dev->pdev, (void *)dev, drm_irq_vgaarb_nokms, NULL);
  
  	/* After installing handler */
  	if (dev->driver->irq_postinstall)
  		ret = dev->driver->irq_postinstall(dev);
  
  	if (ret < 0) {
  		mutex_lock(&dev->struct_mutex);
  		dev->irq_enabled = 0;
  		mutex_unlock(&dev->struct_mutex);
  		if (!drm_core_check_feature(dev, DRIVER_MODESET))
  			vga_client_register(dev->pdev, NULL, NULL, NULL);
  		free_irq(drm_dev_to_irq(dev), dev);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL(drm_irq_install);
  
  /**
   * Uninstall the IRQ handler.
   *
   * \param dev DRM device.
   *
   * Calls the driver's \c drm_driver_irq_uninstall() function, and stops the irq.
   */
  int drm_irq_uninstall(struct drm_device *dev)
  {
  	unsigned long irqflags;
  	int irq_enabled, i;
  
  	if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
  		return -EINVAL;
  
  	mutex_lock(&dev->struct_mutex);
  	irq_enabled = dev->irq_enabled;
  	dev->irq_enabled = 0;
  	mutex_unlock(&dev->struct_mutex);
  
  	/*
  	 * Wake up any waiters so they don't hang.
  	 */
  	if (dev->num_crtcs) {
  		spin_lock_irqsave(&dev->vbl_lock, irqflags);
  		for (i = 0; i < dev->num_crtcs; i++) {
  			DRM_WAKEUP(&dev->vbl_queue[i]);
  			dev->vblank_enabled[i] = 0;
  			dev->last_vblank[i] =
  				dev->driver->get_vblank_counter(dev, i);
  		}
  		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
  	}
  
  	if (!irq_enabled)
  		return -EINVAL;
  
  	DRM_DEBUG("irq=%d\n", drm_dev_to_irq(dev));
  
  	if (!drm_core_check_feature(dev, DRIVER_MODESET))
  		vga_client_register(dev->pdev, NULL, NULL, NULL);
  
  	if (dev->driver->irq_uninstall)
  		dev->driver->irq_uninstall(dev);
  
  	free_irq(drm_dev_to_irq(dev), 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.
  		 */
  		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)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",
  		  crtc, (int)vbl_status, hpos, vpos,
  		  (long)raw_time.tv_sec, (long)raw_time.tv_usec,
  		  (long)vblank_time->tv_sec, (long)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
   *
   * 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);
  
  /**
   * 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)
  {
  	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) {
  		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);
  			if (ret)
  				atomic_dec(&dev->vblank_refcount[crtc]);
  			else {
  				dev->vblank_enabled[crtc] = 1;
  				drm_update_vblank_count(dev, crtc);
  			}
  		}
  		spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags2);
  	} else {
  		if (!dev->vblank_enabled[crtc]) {
  			atomic_dec(&dev->vblank_refcount[crtc]);
  			ret = -EINVAL;
  		}
  	}
  	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
  
  	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))
  		mod_timer(&dev->vblank_disable_timer,
  			  jiffies + ((drm_vblank_offdelay * DRM_HZ)/1000));
  }
  EXPORT_SYMBOL(drm_vblank_put);
  
  void drm_vblank_off(struct drm_device *dev, int crtc)
  {
  	struct drm_pending_vblank_event *e, *t;
  	struct timeval now;
  	unsigned long irqflags;
  	unsigned int seq;
  
  	spin_lock_irqsave(&dev->vbl_lock, irqflags);
  	vblank_disable_and_save(dev, crtc);
  	DRM_WAKEUP(&dev->vbl_queue[crtc]);
  
  	/* Send any queued vblank events, lest the natives grow disquiet */
  	seq = drm_vblank_count_and_time(dev, crtc, &now);
  	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);
  
  		e->event.sequence = seq;
  		e->event.tv_sec = now.tv_sec;
  		e->event.tv_usec = now.tv_usec;
  		drm_vblank_put(dev, e->pipe);
  		list_move_tail(&e->base.link, &e->base.file_priv->event_list);
  		wake_up_interruptible(&e->base.file_priv->event_wait);
  		trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
  						 e->event.sequence);
  	}
  
  	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
  }
  EXPORT_SYMBOL(drm_vblank_off);
  
  /**
   * drm_vblank_pre_modeset - account for vblanks across mode sets
   * @dev: DRM device
   * @crtc: CRTC in question
   * @post: post or pre mode set?
   *
   * 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 ?) */
  	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)
  {
  	unsigned long irqflags;
  
  	if (dev->vblank_inmodeset[crtc]) {
  		spin_lock_irqsave(&dev->vbl_lock, irqflags);
  		dev->vblank_disable_allowed = 1;
  		spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
  
  		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;
  	int ret = 0;
  	unsigned int crtc;
  
  	/* If drm_vblank_init() hasn't been called yet, just no-op */
  	if (!dev->num_crtcs)
  		goto out;
  
  	crtc = modeset->crtc;
  	if (crtc >= dev->num_crtcs) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	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:
  		ret = -EINVAL;
  		break;
  	}
  
  out:
  	return ret;
  }
  
  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 long flags;
  	unsigned int seq;
  	int ret;
  
  	e = kzalloc(sizeof *e, GFP_KERNEL);
  	if (e == NULL) {
  		ret = -ENOMEM;
  		goto err_put;
  	}
  
  	e->pipe = pipe;
  	e->base.pid = current->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 = (void (*) (struct drm_pending_event *)) kfree;
  
  	spin_lock_irqsave(&dev->event_lock, flags);
  
  	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);
  
  	trace_drm_vblank_event_queued(current->pid, pipe,
  				      vblwait->request.sequence);
  
  	e->event.sequence = vblwait->request.sequence;
  	if ((seq - vblwait->request.sequence) <= (1 << 23)) {
  		e->event.sequence = seq;
  		e->event.tv_sec = now.tv_sec;
  		e->event.tv_usec = now.tv_usec;
  		drm_vblank_put(dev, pipe);
  		list_add_tail(&e->base.link, &e->base.file_priv->event_list);
  		wake_up_interruptible(&e->base.file_priv->event_wait);
  		vblwait->reply.sequence = seq;
  		trace_drm_vblank_event_delivered(current->pid, pipe,
  						 vblwait->request.sequence);
  	} 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;
  	}
  
  	spin_unlock_irqrestore(&dev->event_lock, flags);
  
  	return 0;
  
  err_unlock:
  	spin_unlock_irqrestore(&dev->event_lock, flags);
  	kfree(e);
  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 = 0;
  	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;
  	DRM_WAIT_ON(ret, dev->vbl_queue[crtc], 3 * DRM_HZ,
  		    (((drm_vblank_count(dev, crtc) -
  		       vblwait->request.sequence) <= (1 << 23)) ||
  		     !dev->irq_enabled));
  
  	if (ret != -EINTR) {
  		struct timeval 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;
  
  		DRM_DEBUG("returning %d to client\n",
  			  vblwait->reply.sequence);
  	} else {
  		DRM_DEBUG("vblank wait interrupted by signal\n");
  	}
  
  done:
  	drm_vblank_put(dev, crtc);
  	return ret;
  }
  
  void drm_handle_vblank_events(struct drm_device *dev, int crtc)
  {
  	struct drm_pending_vblank_event *e, *t;
  	struct timeval now;
  	unsigned long flags;
  	unsigned int seq;
  
  	seq = drm_vblank_count_and_time(dev, crtc, &now);
  
  	spin_lock_irqsave(&dev->event_lock, flags);
  
  	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);
  
  		e->event.sequence = seq;
  		e->event.tv_sec = now.tv_sec;
  		e->event.tv_usec = now.tv_usec;
  		drm_vblank_put(dev, e->pipe);
  		list_move_tail(&e->base.link, &e->base.file_priv->event_list);
  		wake_up_interruptible(&e->base.file_priv->event_wait);
  		trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
  						 e->event.sequence);
  	}
  
  	spin_unlock_irqrestore(&dev->event_lock, flags);
  
  	trace_drm_vblank_event(crtc, seq);
  }
  
  /**
   * 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;
  	unsigned long irqflags;
  
  	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.
  	 */
  	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 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->vbl_queue[crtc]);
  	drm_handle_vblank_events(dev, crtc);
  
  	spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
  	return true;
  }
  EXPORT_SYMBOL(drm_handle_vblank);
  