gpu/drm/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 "drmP.h"

#include <linux/interrupt.h>	/* For task queue support */

#include <linux/vgaarb.h>
/**
 * 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 (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ))
		return -EINVAL;

	if ((p->busnum >> 8) != drm_get_pci_domain(dev) ||
	    (p->busnum & 0xff) != dev->pdev->bus->number ||
	    p->devnum != PCI_SLOT(dev->pdev->devfn) || p->funcnum != PCI_FUNC(dev->pdev->devfn))
		return -EINVAL;

	p->irq = dev->pdev->irq;

	DRM_DEBUG("%d:%d:%d => IRQ %d\n", p->busnum, p->devnum, p->funcnum,
		  p->irq);

	return 0;
}

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);
			dev->last_vblank[i] =
				dev->driver->get_vblank_counter(dev, i);
			dev->driver->disable_vblank(dev, i);
			dev->vblank_enabled[i] = 0;
		}
		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);

	dev->num_crtcs = 0;
}

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);
	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;

	/* 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)
		dev->driver->irq_uninstall(dev);
	else {
		dev->driver->irq_preinstall(dev);
		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 (dev->pdev->irq == 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", dev->pdev->irq);

	/* Before installing handler */
	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 */
	ret = dev->driver->irq_postinstall(dev);
	if (ret < 0) {
		mutex_lock(&dev->struct_mutex);
		dev->irq_enabled = 0;
		mutex_unlock(&dev->struct_mutex);
	}

	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.
	 */
	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", dev->pdev->irq);

	if (!drm_core_check_feature(dev, DRIVER_MODESET))
		vga_client_register(dev->pdev, NULL, NULL, NULL);

	dev->driver->irq_uninstall(dev);

	free_irq(dev->pdev->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 != dev->pdev->irq)
			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_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_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;

	/*
	 * 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.
	 */
	cur_vblank = dev->driver->get_vblank_counter(dev, crtc);
	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);

	atomic_add(diff, &dev->_vblank_count[crtc]);
}

/**
 * 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;
	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) {
		if (!dev->vblank_enabled[crtc]) {
			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);
			}
		}
	} 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.
 */
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]))
		mod_timer(&dev->vblank_disable_timer, jiffies + 5*DRM_HZ);
}
EXPORT_SYMBOL(drm_vblank_put);

void drm_vblank_off(struct drm_device *dev, int crtc)
{
	unsigned long irqflags;

	spin_lock_irqsave(&dev->vbl_lock, irqflags);
	DRM_WAKEUP(&dev->vbl_queue[crtc]);
	dev->vblank_enabled[crtc] = 0;
	dev->last_vblank[crtc] = dev->driver->get_vblank_counter(dev, crtc);
	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
}
EXPORT_SYMBOL(drm_vblank_off);

/**
 * 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)
{
	/*
	 * 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 crtc, ret = 0;

	/* 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;

	e = kzalloc(sizeof *e, GFP_KERNEL);
	if (e == NULL)
		return -ENOMEM;

	e->pipe = pipe;
	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;

	do_gettimeofday(&now);
	spin_lock_irqsave(&dev->event_lock, flags);

	if (file_priv->event_space < sizeof e->event) {
		spin_unlock_irqrestore(&dev->event_lock, flags);
		kfree(e);
		return -ENOMEM;
	}

	file_priv->event_space -= sizeof e->event;
	seq = drm_vblank_count(dev, pipe);
	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);

	e->event.sequence = vblwait->request.sequence;
	if ((seq - vblwait->request.sequence) <= (1 << 23)) {
		e->event.tv_sec = now.tv_sec;
		e->event.tv_usec = now.tv_usec;
		drm_vblank_put(dev, e->pipe);
		list_add_tail(&e->base.link, &e->base.file_priv->event_list);
		wake_up_interruptible(&e->base.file_priv->event_wait);
	} else {
		list_add_tail(&e->base.link, &dev->vblank_event_list);
	}

	spin_unlock_irqrestore(&dev->event_lock, flags);

	return 0;
}

/**
 * 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;

	if ((!dev->pdev->irq) || (!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_ERROR("Unsupported type value 0x%x, supported mask 0x%x\n",
			  vblwait->request.type,
			  (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_FLAGS_MASK));
		return -EINVAL;
	}

	flags = vblwait->request.type & _DRM_VBLANK_FLAGS_MASK;
	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)
		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;

		do_gettimeofday(&now);

		vblwait->reply.tval_sec = now.tv_sec;
		vblwait->reply.tval_usec = now.tv_usec;
		vblwait->reply.sequence = drm_vblank_count(dev, crtc);
		DRM_DEBUG("returning %d to client\n",
			  vblwait->reply.sequence);
	} else {
		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;

	do_gettimeofday(&now);
	seq = drm_vblank_count(dev, crtc);

	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);
	}

	spin_unlock_irqrestore(&dev->event_lock, flags);
}

/**
 * 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.
 */
void drm_handle_vblank(struct drm_device *dev, int crtc)
{
	if (!dev->num_crtcs)
		return;

	atomic_inc(&dev->_vblank_count[crtc]);
	DRM_WAKEUP(&dev->vbl_queue[crtc]);
	drm_handle_vblank_events(dev, crtc);
}
EXPORT_SYMBOL(drm_handle_vblank);