drm_irq.c

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/*
 * Created: Fri Mar 19 14:30:16 1999 by [email protected]
 *
 * 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 <drm/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

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_sync(&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);
    }
}

int drm_irq_install(struct drm_device *dev)
{
    int ret;
    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);

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);

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;
    }
}

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);

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);

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 gettimeofday timestamp as best estimate.
     */
    do_gettimeofday(tvblank);

    return 0;
}
EXPORT_SYMBOL(drm_get_last_vbltimestamp);

u32 drm_vblank_count(struct drm_device *dev, int crtc)
{
    return atomic_read(&dev->_vblank_count[crtc]);
}
EXPORT_SYMBOL(drm_vblank_count);

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 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();
}

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);

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);

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);

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 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;
}

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;
    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;
}

static 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);
}

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);