gpu/drm/drm_vblank.c

/*
 * drm_irq.c IRQ and vblank support
 *
 * \author Rickard E. (Rik) Faith <faith@valinux.com>
 * \author Gareth Hughes <gareth@valinux.com>
 *
 * 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 <linux/export.h>
#include <linux/kthread.h>
#include <linux/moduleparam.h>

#include <drm/drm_crtc.h>
#include <drm/drm_drv.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_managed.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_print.h>
#include <drm/drm_vblank.h>

#include "drm_internal.h"
#include "drm_trace.h"

/**
 * DOC: vblank handling
 *
 * From the computer's perspective, every time the monitor displays
 * a new frame the scanout engine has "scanned out" the display image
 * from top to bottom, one row of pixels at a time. The current row
 * of pixels is referred to as the current scanline.
 *
 * In addition to the display's visible area, there's usually a couple of
 * extra scanlines which aren't actually displayed on the screen.
 * These extra scanlines don't contain image data and are occasionally used
 * for features like audio and infoframes. The region made up of these
 * scanlines is referred to as the vertical blanking region, or vblank for
 * short.
 *
 * For historical reference, the vertical blanking period was designed to
 * give the electron gun (on CRTs) enough time to move back to the top of
 * the screen to start scanning out the next frame. Similar for horizontal
 * blanking periods. They were designed to give the electron gun enough
 * time to move back to the other side of the screen to start scanning the
 * next scanline.
 *
 * ::
 *
 *
 *    physical →   ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽
 *    top of      |                                        |
 *    display     |                                        |
 *                |               New frame                |
 *                |                                        |
 *                |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓|
 *                |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| ← Scanline,
 *                |↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓|   updates the
 *                |                                        |   frame as it
 *                |                                        |   travels down
 *                |                                        |   ("sacn out")
 *                |               Old frame                |
 *                |                                        |
 *                |                                        |
 *                |                                        |
 *                |                                        |   physical
 *                |                                        |   bottom of
 *    vertical    |⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽| ← display
 *    blanking    ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *    region   →  ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *                ┆xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx┆
 *    start of →   ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽
 *    new frame
 *
 * "Physical top of display" is the reference point for the high-precision/
 * corrected timestamp.
 *
 * On a lot of display hardware, programming needs to take effect during the
 * vertical blanking period so that settings like gamma, the image buffer
 * buffer to be scanned out, etc. can safely be changed without showing
 * any visual artifacts on the screen. In some unforgiving hardware, some of
 * this programming has to both start and end in the same vblank. To help
 * with the timing of the hardware programming, an interrupt is usually
 * available to notify the driver when it can start the updating of registers.
 * The interrupt is in this context named the vblank interrupt.
 *
 * The vblank interrupt may be fired at different points depending on the
 * hardware. Some hardware implementations will fire the interrupt when the
 * new frame start, other implementations will fire the interrupt at different
 * points in time.
 *
 * Vertical blanking plays a major role in graphics rendering. To achieve
 * tear-free display, users must synchronize page flips and/or rendering to
 * vertical blanking. The DRM API offers ioctls to perform page flips
 * synchronized to vertical blanking and wait for vertical blanking.
 *
 * The DRM core handles most of the vertical blanking management logic, which
 * involves filtering out spurious interrupts, keeping race-free blanking
 * counters, coping with counter wrap-around and resets and keeping use counts.
 * It relies on the driver to generate vertical blanking interrupts and
 * optionally provide a hardware vertical blanking counter.
 *
 * Drivers must initialize the vertical blanking handling core with a call to
 * drm_vblank_init(). Minimally, a driver needs to implement
 * &drm_crtc_funcs.enable_vblank and &drm_crtc_funcs.disable_vblank plus call
 * drm_crtc_handle_vblank() in its vblank interrupt handler for working vblank
 * support.
 *
 * Vertical blanking interrupts can be enabled by the DRM core or by drivers
 * themselves (for instance to handle page flipping operations).  The DRM core
 * maintains a vertical blanking use count to ensure that the interrupts are not
 * disabled while a user still needs them. To increment the use count, drivers
 * call drm_crtc_vblank_get() and release the vblank reference again with
 * drm_crtc_vblank_put(). In between these two calls vblank interrupts are
 * guaranteed to be enabled.
 *
 * On many hardware disabling the vblank interrupt cannot be done in a race-free
 * manner, see &drm_driver.vblank_disable_immediate and
 * &drm_driver.max_vblank_count. In that case the vblank core only disables the
 * vblanks after a timer has expired, which can be configured through the
 * ``vblankoffdelay`` module parameter.
 *
 * Drivers for hardware without support for vertical-blanking interrupts
 * must not call drm_vblank_init(). For such drivers, atomic helpers will
 * automatically generate fake vblank events as part of the display update.
 * This functionality also can be controlled by the driver by enabling and
 * disabling struct drm_crtc_state.no_vblank.
 */

/* 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

static bool drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, ktime_t *tvblank, bool in_vblank_irq);

static unsigned int drm_timestamp_precision = 20; /* Default to 20 usecs. */

static int drm_vblank_offdelay = 5000; /* Default to 5000 msecs. */

module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
MODULE_PARM_DESC(vblankoffdelay,
                 "Delay until vblank irq auto-disable [msecs] (0: never disable, <0: disable immediately)");
MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");

static void store_vblank(struct drm_device *dev, unsigned int pipe, u32 vblank_count_inc, ktime_t t_vblank, u32 last)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    assert_spin_locked(&dev->vblank_time_lock);

    vblank->last = last;

    write_seqlock(&vblank->seqlock);
    vblank->time = t_vblank;
    atomic64_add(vblank_count_inc, &vblank->count);
    write_sequnlock(&vblank->seqlock);
}

static u32 drm_max_vblank_count(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    return vblank->max_vblank_count ?: dev->max_vblank_count;
}

/*
 * "No hw counter" fallback implementation of .get_vblank_counter() hook,
 * if there is no useable hardware frame counter available.
 */
static u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe)
{
    drm_WARN_ON_ONCE(dev, drm_max_vblank_count(dev, pipe) != 0);
    return 0;
}

static u32 _get_vblank_counter(struct drm_device *dev, unsigned int pipe)
{
    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
        struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

        if (drm_WARN_ON(dev, !crtc)) {
            return 0;
        }

        if (crtc->funcs->get_vblank_counter) {
            return crtc->funcs->get_vblank_counter(crtc);
        }
    } else if (dev->driver->get_vblank_counter) {
        return dev->driver->get_vblank_counter(dev, pipe);
    }

    return drm_vblank_no_hw_counter(dev, pipe);
}

/*
 * Reset the stored timestamp for the current vblank count to correspond
 * to the last vblank occurred.
 *
 * Only to be called from drm_crtc_vblank_on().
 *
 * Note: caller must hold &drm_device.vbl_lock since this reads & writes
 * device vblank fields.
 */
static void drm_reset_vblank_timestamp(struct drm_device *dev, unsigned int pipe)
{
    u32 cur_vblank;
    bool rc;
    ktime_t t_vblank;
    int count = DRM_TIMESTAMP_MAXRETRIES;

    spin_lock(&dev->vblank_time_lock);

    /*
     * sample the current counter to avoid random jumps
     * when drm_vblank_enable() applies the diff
     */
    do {
        cur_vblank = _get_vblank_counter(dev, pipe);
        rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
    } while (cur_vblank != _get_vblank_counter(dev, pipe) && --count > 0);

    /*
     * Only reinitialize corresponding vblank timestamp if high-precision query
     * available and didn't fail. Otherwise reinitialize delayed at next vblank
     * interrupt and assign 0 for now, to mark the vblanktimestamp as invalid.
     */
    if (!rc) {
        t_vblank = 0;
    }

    /*
     * +1 to make sure user will never see the same
     * vblank counter value before and after a modeset
     */
    store_vblank(dev, pipe, 1, t_vblank, cur_vblank);

    spin_unlock(&dev->vblank_time_lock);
}

/*
 * Call back into the driver to update the appropriate vblank counter
 * (specified by @pipe).  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 &drm_device.vbl_lock since this reads & writes
 * device vblank fields.
 */
static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, bool in_vblank_irq)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    u32 cur_vblank, diff;
    bool rc;
    ktime_t t_vblank;
    int count = DRM_TIMESTAMP_MAXRETRIES;
    int framedur_ns = vblank->framedur_ns;
    u32 max_vblank_count = drm_max_vblank_count(dev, pipe);

    /*
     * 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 + 1 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 = _get_vblank_counter(dev, pipe);
        rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq);
    } while (cur_vblank != _get_vblank_counter(dev, pipe) && --count > 0);

    if (max_vblank_count) {
        /* trust the hw counter when it's around */
        diff = (cur_vblank - vblank->last) & max_vblank_count;
    } else if (rc && framedur_ns) {
        u64 diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));

        /*
         * Figure out how many vblanks we've missed based
         * on the difference in the timestamps and the
         * frame/field duration.
         */

        drm_dbg_vbl(dev,
                    "crtc %u: Calculating number of vblanks."
                    " diff_ns = %lld, framedur_ns = %d)\n",
                    pipe, (long long)diff_ns, framedur_ns);

        diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);
        if (diff == 0 && in_vblank_irq) {
            drm_dbg_vbl(dev, "crtc %u: Redundant vblirq ignored\n", pipe);
        }
    } else {
        /* some kind of default for drivers w/o accurate vbl timestamping */
        diff = in_vblank_irq ? 1 : 0;
    }

    /*
     * Within a drm_vblank_pre_modeset - drm_vblank_post_modeset
     * interval? If so then vblank irqs keep running and it will likely
     * happen that the hardware vblank counter is not trustworthy as it
     * might reset at some point in that interval and vblank timestamps
     * are not trustworthy either in that interval. Iow. this can result
     * in a bogus diff >> 1 which must be avoided as it would cause
     * random large forward jumps of the software vblank counter.
     */
    if (diff > 1 && (vblank->inmodeset & 0x2)) {
        drm_dbg_vbl(dev,
                    "clamping vblank bump to 1 on crtc %u: diffr=%u"
                    " due to pre-modeset.\n",
                    pipe, diff);
        diff = 1;
    }

    drm_dbg_vbl(dev,
                "updating vblank count on crtc %u:"
                " current=%llu, diff=%u, hw=%u hw_last=%u\n",
                pipe, (unsigned long long)atomic64_read(&vblank->count), diff, cur_vblank, vblank->last);

    if (diff == 0) {
        drm_WARN_ON_ONCE(dev, cur_vblank != vblank->last);
        return;
    }

    /*
     * Only reinitialize corresponding vblank timestamp if high-precision query
     * available and didn't fail, or we were called from the vblank interrupt.
     * Otherwise reinitialize delayed at next vblank interrupt and assign 0
     * for now, to mark the vblanktimestamp as invalid.
     */
    if (!rc && !in_vblank_irq) {
        t_vblank = 0;
    }

    store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
}

u64 drm_vblank_count(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    u64 count;

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return 0;
    }

    count = atomic64_read(&vblank->count);

    /*
     * This read barrier corresponds to the implicit write barrier of the
     * write seqlock in store_vblank(). Note that this is the only place
     * where we need an explicit barrier, since all other access goes
     * through drm_vblank_count_and_time(), which already has the required
     * read barrier curtesy of the read seqlock.
     */
    smp_rmb();

    return count;
}

/**
 * drm_crtc_accurate_vblank_count - retrieve the master vblank counter
 * @crtc: which counter to retrieve
 *
 * This function is similar to drm_crtc_vblank_count() but this function
 * interpolates to handle a race with vblank interrupts using the high precision
 * timestamping support.
 *
 * This is mostly useful for hardware that can obtain the scanout position, but
 * doesn't have a hardware frame counter.
 */
u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    u64 vblank;
    unsigned long flags;

    drm_WARN_ONCE(dev, drm_debug_enabled(DRM_UT_VBL) && !crtc->funcs->get_vblank_timestamp,
                  "This function requires support for accurate vblank timestamps.");

    spin_lock_irqsave(&dev->vblank_time_lock, flags);

    drm_update_vblank_count(dev, pipe, false);
    vblank = drm_vblank_count(dev, pipe);

    spin_unlock_irqrestore(&dev->vblank_time_lock, flags);

    return vblank;
}
EXPORT_SYMBOL(drm_crtc_accurate_vblank_count);

static void _disable_vblank(struct drm_device *dev, unsigned int pipe)
{
    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
        struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

        if (drm_WARN_ON(dev, !crtc)) {
            return;
        }

        if (crtc->funcs->disable_vblank) {
            crtc->funcs->disable_vblank(crtc);
        }
    } else {
        dev->driver->disable_vblank(dev, pipe);
    }
}

/*
 * 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.
 */
void drm_vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    unsigned long irqflags;

    assert_spin_locked(&dev->vbl_lock);

    /* 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);

    /*
     * Update vblank count and disable vblank interrupts only if the
     * interrupts were enabled. This avoids calling the ->disable_vblank()
     * operation in atomic context with the hardware potentially runtime
     * suspended.
     */
    if (!vblank->enabled) {
        goto out;
    }

    /*
     * Update the count and timestamp to maintain the
     * appearance that the counter has been ticking all along until
     * this time. This makes the count account for the entire time
     * between drm_crtc_vblank_on() and drm_crtc_vblank_off().
     */
    drm_update_vblank_count(dev, pipe, false);
    _disable_vblank(dev, pipe);
    vblank->enabled = false;

out:
    spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
}

static void vblank_disable_fn(struct timer_list *t)
{
    struct drm_vblank_crtc *vblank = from_timer(vblank, t, disable_timer);
    struct drm_device *dev = vblank->dev;
    unsigned int pipe = vblank->pipe;
    unsigned long irqflags;

    spin_lock_irqsave(&dev->vbl_lock, irqflags);
    if (atomic_read(&vblank->refcount) == 0 && vblank->enabled) {
        drm_dbg_core(dev, "disabling vblank on crtc %u\n", pipe);
        drm_vblank_disable_and_save(dev, pipe);
    }
    spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
}

static void drm_vblank_init_release(struct drm_device *dev, void *ptr)
{
    struct drm_vblank_crtc *vblank = ptr;

    drm_WARN_ON(dev, READ_ONCE(vblank->enabled) && drm_core_check_feature(dev, DRIVER_MODESET));

    drm_vblank_destroy_worker(vblank);
    del_timer_sync(&vblank->disable_timer);
}

/**
 * drm_vblank_init - initialize vblank support
 * @dev: DRM device
 * @num_crtcs: number of CRTCs supported by @dev
 *
 * This function initializes vblank support for @num_crtcs display pipelines.
 * Cleanup is handled automatically through a cleanup function added with
 * drmm_add_action_or_reset().
 *
 * Returns:
 * Zero on success or a negative error code on failure.
 */
int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
{
    int ret;
    unsigned int i;

    spin_lock_init(&dev->vbl_lock);
    spin_lock_init(&dev->vblank_time_lock);

    dev->vblank = drmm_kcalloc(dev, num_crtcs, sizeof(*dev->vblank), GFP_KERNEL);
    if (!dev->vblank) {
        return -ENOMEM;
    }

    dev->num_crtcs = num_crtcs;

    for (i = 0; i < num_crtcs; i++) {
        struct drm_vblank_crtc *vblank = &dev->vblank[i];

        vblank->dev = dev;
        vblank->pipe = i;
        init_waitqueue_head(&vblank->queue);
        timer_setup(&vblank->disable_timer, vblank_disable_fn, 0);
        seqlock_init(&vblank->seqlock);

        ret = drmm_add_action_or_reset(dev, drm_vblank_init_release, vblank);
        if (ret) {
            return ret;
        }

        ret = drm_vblank_worker_init(vblank);
        if (ret) {
            return ret;
        }
    }

    return 0;
}
EXPORT_SYMBOL(drm_vblank_init);

/**
 * drm_dev_has_vblank - test if vblanking has been initialized for
 *                      a device
 * @dev: the device
 *
 * Drivers may call this function to test if vblank support is
 * initialized for a device. For most hardware this means that vblanking
 * can also be enabled.
 *
 * Atomic helpers use this function to initialize
 * &drm_crtc_state.no_vblank. See also drm_atomic_helper_check_modeset().
 *
 * Returns:
 * True if vblanking has been initialized for the given device, false
 * otherwise.
 */
bool drm_dev_has_vblank(const struct drm_device *dev)
{
    return dev->num_crtcs != 0;
}
EXPORT_SYMBOL(drm_dev_has_vblank);

/**
 * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC
 * @crtc: which CRTC's vblank waitqueue to retrieve
 *
 * This function returns a pointer to the vblank waitqueue for the CRTC.
 * Drivers can use this to implement vblank waits using wait_event() and related
 * functions.
 */
wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc)
{
    return &crtc->dev->vblank[drm_crtc_index(crtc)].queue;
}
EXPORT_SYMBOL(drm_crtc_vblank_waitqueue);

/**
 * drm_calc_timestamping_constants - calculate vblank timestamp constants
 * @crtc: drm_crtc whose timestamp constants should be updated.
 * @mode: display mode containing the scanout timings
 *
 * Calculate and store various constants which are later needed by vblank and
 * swap-completion timestamping, e.g, by
 * drm_crtc_vblank_helper_get_vblank_timestamp(). They are derived from
 * CRTC's true scanout timing, so they take things like panel scaling or
 * other adjustments into account.
 */
void drm_calc_timestamping_constants(struct drm_crtc *crtc, const struct drm_display_mode *mode)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    int linedur_ns = 0, framedur_ns = 0;
    int dotclock = mode->crtc_clock;

    if (!drm_dev_has_vblank(dev)) {
        return;
    }

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    /* Valid dotclock? */
    if (dotclock > 0) {
        int frame_size = mode->crtc_htotal * mode->crtc_vtotal;

        /*
         * Convert scanline length in pixels and video
         * dot clock to line duration and frame duration
         * in nanoseconds:
         */
        linedur_ns = div_u64((u64)mode->crtc_htotal * 0xf4240, dotclock);
        framedur_ns = div_u64((u64)frame_size * 0xf4240, dotclock);

        /*
         * Fields of interlaced scanout modes are only half a frame duration.
         */
        if (mode->flags & DRM_MODE_FLAG_INTERLACE) {
            framedur_ns /= 0x2;
        }
    } else {
        drm_err(dev, "crtc %u: Can't calculate constants, dotclock = 0!\n", crtc->base.id);
    }

    vblank->linedur_ns = linedur_ns;
    vblank->framedur_ns = framedur_ns;
    vblank->hwmode = *mode;

    drm_dbg_core(dev, "crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n", crtc->base.id, mode->crtc_htotal,
                 mode->crtc_vtotal, mode->crtc_vdisplay);
    drm_dbg_core(dev, "crtc %u: clock %d kHz framedur %d linedur %d\n", crtc->base.id, dotclock, framedur_ns,
                 linedur_ns);
}
EXPORT_SYMBOL(drm_calc_timestamping_constants);

/**
 * drm_crtc_vblank_helper_get_vblank_timestamp_internal - precise vblank
 *                                                        timestamp helper
 * @crtc: CRTC whose 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 time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 * @get_scanout_position:
 *     Callback function to retrieve the scanout position. See
 *     @struct drm_crtc_helper_funcs.get_scanout_position.
 *
 * Implements calculation of exact vblank timestamps from given drm_display_mode
 * timings and current video scanout position of a CRTC.
 *
 * The current implementation only handles standard video modes. For double scan
 * and interlaced modes the driver is supposed to adjust the hardware mode
 * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
 * match the scanout position reported.
 *
 * Note that atomic drivers must call drm_calc_timestamping_constants() before
 * enabling a CRTC. The atomic helpers already take care of that in
 * drm_atomic_helper_calc_timestamping_constants().
 *
 * Returns:bool
 *
 * Returns true on success, and false on failure, i.e. when no accurate
 * timestamp could be acquired.
 */
bool drm_crtc_vblank_helper_get_vblank_timestamp_internal(struct drm_crtc *crtc, int *max_error, ktime_t *vblank_time,
                                                          bool in_vblank_irq,
                                                          drm_vblank_get_scanout_position_func get_scanout_position)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = crtc->index;
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    struct timespec64 ts_etime, ts_vblank_time;
    ktime_t stime, etime;
    bool vbl_status;
    const struct drm_display_mode *mode;
    int vpos, hpos, i;
    int delta_ns, duration_ns;

    if (pipe >= dev->num_crtcs) {
        drm_err(dev, "Invalid crtc %u\n", pipe);
        return false;
    }

    /* Scanout position query not supported? Should not happen. */
    if (!get_scanout_position) {
        drm_err(dev, "Called from CRTC w/o get_scanout_position()!?\n");
        return false;
    }

    if (drm_drv_uses_atomic_modeset(dev)) {
        mode = &vblank->hwmode;
    } else {
        mode = &crtc->hwmode;
    }

    /* If mode timing undefined, just return as no-op:
     * Happens during initial modesetting of a crtc.
     */
    if (mode->crtc_clock == 0) {
        drm_dbg_core(dev, "crtc %u: Noop due to uninitialized mode.\n", pipe);
        drm_WARN_ON_ONCE(dev, drm_drv_uses_atomic_modeset(dev));
        return false;
    }

    /* 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++) {
        /*
         * Get vertical and horizontal scanout position vpos, hpos,
         * and bounding timestamps stime, etime, pre/post query.
         */
        vbl_status = get_scanout_position(crtc, in_vblank_irq, &vpos, &hpos, &stime, &etime, mode);
        /* Return as no-op if scanout query unsupported or failed. */
        if (!vbl_status) {
            drm_dbg_core(dev, "crtc %u : scanoutpos query failed.\n", pipe);
            return false;
        }

        /* Compute uncertainty in timestamp of scanout position query. */
        duration_ns = ktime_to_ns(etime) - ktime_to_ns(stime);
        /* Accept result with <  max_error nsecs timing uncertainty. */
        if (duration_ns <= *max_error) {
            break;
        }
    }

    /* Noisy system timing? */
    if (i == DRM_TIMESTAMP_MAXRETRIES) {
        drm_dbg_core(dev, "crtc %u: Noisy timestamp %d us > %d us [%d reps].\n", pipe, duration_ns / 0x3e8,
                     *max_error / 0x3e8, i);
    }

    /* Return upper bound of timestamp precision error. */
    *max_error = duration_ns;

    /* 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 = div_s64(1000000LL * (vpos * mode->crtc_htotal + hpos), mode->crtc_clock);

    /* Subtract time delta from raw timestamp to get final
     * vblank_time timestamp for end of vblank.
     */
    *vblank_time = ktime_sub_ns(etime, delta_ns);

    if (!drm_debug_enabled(DRM_UT_VBL)) {
        return true;
    }

    ts_etime = ktime_to_timespec64(etime);
    ts_vblank_time = ktime_to_timespec64(*vblank_time);

    drm_dbg_vbl(dev, "crtc %u : v p(%d,%d)@ %lld.%06ld -> %lld.%06ld [e %d us, %d rep]\n", pipe, hpos, vpos,
                (u64)ts_etime.tv_sec, ts_etime.tv_nsec / 0x3e8, (u64)ts_vblank_time.tv_sec,
                ts_vblank_time.tv_nsec / 0x3e8, duration_ns / 0x3e8, i);

    return true;
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_internal);

/**
 * drm_crtc_vblank_helper_get_vblank_timestamp - precise vblank timestamp
 *                                               helper
 * @crtc: CRTC whose 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 time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 *
 * Implements calculation of exact vblank timestamps from given drm_display_mode
 * timings and current video scanout position of a CRTC. This can be directly
 * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
 * driver if &drm_crtc_helper_funcs.get_scanout_position is implemented.
 *
 * The current implementation only handles standard video modes. For double scan
 * and interlaced modes the driver is supposed to adjust the hardware mode
 * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
 * match the scanout position reported.
 *
 * Note that atomic drivers must call drm_calc_timestamping_constants() before
 * enabling a CRTC. The atomic helpers already take care of that in
 * drm_atomic_helper_calc_timestamping_constants().
 *
 * Returns:bool
 *
 * Returns true on success, and false on failure, i.e. when no accurate
 * timestamp could be acquired.
 */
bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc, int *max_error, ktime_t *vblank_time,
                                                 bool in_vblank_irq)
{
    return drm_crtc_vblank_helper_get_vblank_timestamp_internal(crtc, max_error, vblank_time, in_vblank_irq,
                                                                crtc->helper_private->get_scanout_position);
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);

/**
 * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
 *                             vblank interval
 * @dev: DRM device
 * @pipe: index of CRTC whose vblank timestamp to retrieve
 * @tvblank: Pointer to target time which should receive the timestamp
 * @in_vblank_irq:
 *     True when called from drm_crtc_handle_vblank().  Some drivers
 *     need to apply some workarounds for gpu-specific vblank irq quirks
 *     if flag is set.
 *
 * 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:
 * True if timestamp is considered to be very precise, false otherwise.
 */
static bool drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, ktime_t *tvblank, bool in_vblank_irq)
{
    struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
    bool ret = false;

    /* Define requested maximum error on timestamps (nanoseconds). */
    int max_error = (int)drm_timestamp_precision * 1000;

    /* Query driver if possible and precision timestamping enabled. */
    if (crtc && crtc->funcs->get_vblank_timestamp && max_error > 0) {
        struct drm_crtc *crtc_ex = drm_crtc_from_index(dev, pipe);

        ret = crtc_ex->funcs->get_vblank_timestamp(crtc_ex, &max_error, tvblank, in_vblank_irq);
    }

    /* GPU high precision timestamp query unsupported or failed.
     * Return current monotonic/gettimeofday timestamp as best estimate.
     */
    if (!ret) {
        *tvblank = ktime_get();
    }

    return ret;
}

/**
 * drm_crtc_vblank_count - retrieve "cooked" vblank counter value
 * @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. Note that this timer isn't correct against a racing
 * vblank interrupt (since it only reports the software vblank counter), see
 * drm_crtc_accurate_vblank_count() for such use-cases.
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 *
 * Returns:
 * The software vblank counter.
 */
u64 drm_crtc_vblank_count(struct drm_crtc *crtc)
{
    return drm_vblank_count(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_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
 * @pipe: index of CRTC whose counter to retrieve
 * @vblanktime: Pointer to ktime_t 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 vblank counter value.
 *
 * This is the legacy version of drm_crtc_vblank_count_and_time().
 */
static u64 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe, ktime_t *vblanktime)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    u64 vblank_count;
    unsigned int seq;

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        *vblanktime = 0;
        return 0;
    }

    do {
        seq = read_seqbegin(&vblank->seqlock);
        vblank_count = atomic64_read(&vblank->count);
        *vblanktime = vblank->time;
    } while (read_seqretry(&vblank->seqlock, seq));

    return vblank_count;
}

/**
 * drm_crtc_vblank_count_and_time - retrieve "cooked" vblank counter value
 *     and the system timestamp corresponding to that vblank counter value
 * @crtc: which counter to retrieve
 * @vblanktime: Pointer to time 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 vblank counter value.
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 */
u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc, ktime_t *vblanktime)
{
    return drm_vblank_count_and_time(crtc->dev, drm_crtc_index(crtc), vblanktime);
}
EXPORT_SYMBOL(drm_crtc_vblank_count_and_time);

static void send_vblank_event(struct drm_device *dev, struct drm_pending_vblank_event *e, u64 seq, ktime_t now)
{
    struct timespec64 tv;

    switch (e->event.base.type) {
        case DRM_EVENT_VBLANK:
        case DRM_EVENT_FLIP_COMPLETE:
            tv = ktime_to_timespec64(now);
            e->event.vbl.sequence = seq;
            /*
             * e->event is a user space structure, with hardcoded unsigned
             * 32-bit seconds/microseconds. This is safe as we always use
             * monotonic timestamps since linux-4.15
             */
            e->event.vbl.tv_sec = tv.tv_sec;
            e->event.vbl.tv_usec = tv.tv_nsec / 0x3e8;
            break;
        case DRM_EVENT_CRTC_SEQUENCE:
            if (seq) {
                e->event.seq.sequence = seq;
            }
            e->event.seq.time_ns = ktime_to_ns(now);
            break;
    }
    trace_drm_vblank_event_delivered(e->base.file_priv, e->pipe, seq);
    /*
     * Use the same timestamp for any associated fence signal to avoid
     * mismatch in timestamps for vsync & fence events triggered by the
     * same HW event. Frameworks like SurfaceFlinger in Android expects the
     * retire-fence timestamp to match exactly with HW vsync as it uses it
     * for its software vsync modeling.
     */
    drm_send_event_timestamp_locked(dev, &e->base, now);
}

/**
 * drm_crtc_arm_vblank_event - arm vblank event after pageflip
 * @crtc: the source CRTC of the vblank event
 * @e: the event to send
 *
 * A lot of drivers need to generate vblank events for the very next vblank
 * interrupt. For example when the page flip interrupt happens when the page
 * flip gets armed, but not when it actually executes within the next vblank
 * period. This helper function implements exactly the required vblank arming
 * behaviour.
 *
 * NOTE: Drivers using this to send out the &drm_crtc_state.event as part of an
 * atomic commit must ensure that the next vblank happens at exactly the same
 * time as the atomic commit is committed to the hardware. This function itself
 * does **not** protect against the next vblank interrupt racing with either this
 * function call or the atomic commit operation. A possible sequence could be:
 *
 * 1. Driver commits new hardware state into vblank-synchronized registers.
 * 2. A vblank happens, committing the hardware state. Also the corresponding
 *    vblank interrupt is fired off and fully processed by the interrupt
 *    handler.
 * 3. The atomic commit operation proceeds to call drm_crtc_arm_vblank_event().
 * 4. The event is only send out for the next vblank, which is wrong.
 *
 * An equivalent race can happen when the driver calls
 * drm_crtc_arm_vblank_event() before writing out the new hardware state.
 *
 * The only way to make this work safely is to prevent the vblank from firing
 * (and the hardware from committing anything else) until the entire atomic
 * commit sequence has run to completion. If the hardware does not have such a
 * feature (e.g. using a "go" bit), then it is unsafe to use this functions.
 * Instead drivers need to manually send out the event from their interrupt
 * handler by calling drm_crtc_send_vblank_event() and make sure that there's no
 * possible race with the hardware committing the atomic update.
 *
 * Caller must hold a vblank reference for the event @e acquired by a
 * drm_crtc_vblank_get(), which will be dropped when the next vblank arrives.
 */
void drm_crtc_arm_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);

    assert_spin_locked(&dev->event_lock);

    e->pipe = pipe;
    e->sequence = drm_crtc_accurate_vblank_count(crtc) + 1;
    list_add_tail(&e->base.link, &dev->vblank_event_list);
}
EXPORT_SYMBOL(drm_crtc_arm_vblank_event);

/**
 * drm_crtc_send_vblank_event - helper to send vblank event after pageflip
 * @crtc: the source CRTC of the vblank event
 * @e: the event to send
 *
 * Updates sequence # and timestamp on event for the most recently processed
 * vblank, and sends it to userspace.  Caller must hold event lock.
 *
 * See drm_crtc_arm_vblank_event() for a helper which can be used in certain
 * situation, especially to send out events for atomic commit operations.
 */
void drm_crtc_send_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e)
{
    struct drm_device *dev = crtc->dev;
    u64 seq;
    unsigned int pipe = drm_crtc_index(crtc);
    ktime_t now;

    if (drm_dev_has_vblank(dev)) {
        seq = drm_vblank_count_and_time(dev, pipe, &now);
    } else {
        seq = 0;

        now = ktime_get();
    }
    e->pipe = pipe;
    send_vblank_event(dev, e, seq, now);
}
EXPORT_SYMBOL(drm_crtc_send_vblank_event);

static int _enable_vblank(struct drm_device *dev, unsigned int pipe)
{
    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
        struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

        if (drm_WARN_ON(dev, !crtc)) {
            return 0;
        }

        if (crtc->funcs->enable_vblank) {
            return crtc->funcs->enable_vblank(crtc);
        }
    } else if (dev->driver->enable_vblank) {
        return dev->driver->enable_vblank(dev, pipe);
    }

    return -EINVAL;
}

static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    int ret = 0;

    assert_spin_locked(&dev->vbl_lock);

    spin_lock(&dev->vblank_time_lock);

    if (!vblank->enabled) {
        /*
         * 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 = _enable_vblank(dev, pipe);
        drm_dbg_core(dev, "enabling vblank on crtc %u, ret: %d\n", pipe, ret);
        if (ret) {
            atomic_dec(&vblank->refcount);
        } else {
            drm_update_vblank_count(dev, pipe, 0);
            /* drm_update_vblank_count() includes a wmb so we just
             * need to ensure that the compiler emits the write
             * to mark the vblank as enabled after the call
             * to drm_update_vblank_count().
             */
            WRITE_ONCE(vblank->enabled, true);
        }
    }

    spin_unlock(&dev->vblank_time_lock);

    return ret;
}

int drm_vblank_get(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    unsigned long irqflags;
    int ret = 0;

    if (!drm_dev_has_vblank(dev)) {
        return -EINVAL;
    }

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return -EINVAL;
    }

    spin_lock_irqsave(&dev->vbl_lock, irqflags);
    /* Going from 0->1 means we have to enable interrupts again */
    if (atomic_add_return(1, &vblank->refcount) == 1) {
        ret = drm_vblank_enable(dev, pipe);
    } else {
        if (!vblank->enabled) {
            atomic_dec(&vblank->refcount);
            ret = -EINVAL;
        }
    }
    spin_unlock_irqrestore(&dev->vbl_lock, irqflags);

    return ret;
}

/**
 * drm_crtc_vblank_get - get a reference count on vblank events
 * @crtc: which CRTC to own
 *
 * Acquire a reference count on vblank events to avoid having them disabled
 * while in use.
 *
 * Returns:
 * Zero on success or a negative error code on failure.
 */
int drm_crtc_vblank_get(struct drm_crtc *crtc)
{
    return drm_vblank_get(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_get);

void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    if (drm_WARN_ON(dev, atomic_read(&vblank->refcount) == 0)) {
        return;
    }

    /* Last user schedules interrupt disable */
    if (atomic_dec_and_test(&vblank->refcount)) {
        if (drm_vblank_offdelay == 0) {
            return;
        } else if (drm_vblank_offdelay < 0) {
            vblank_disable_fn(&vblank->disable_timer);
        } else if (!dev->vblank_disable_immediate) {
            mod_timer(&vblank->disable_timer, jiffies + ((drm_vblank_offdelay * HZ) / 0x3e8));
        }
    }
}

/**
 * drm_crtc_vblank_put - give up ownership of vblank events
 * @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_crtc_vblank_put(struct drm_crtc *crtc)
{
    drm_vblank_put(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_put);

/**
 * drm_wait_one_vblank - wait for one vblank
 * @dev: DRM device
 * @pipe: CRTC index
 *
 * This waits for one vblank to pass on @pipe, using the irq driver interfaces.
 * It is a failure to call this when the vblank irq for @pipe is disabled, e.g.
 * due to lack of driver support or because the crtc is off.
 *
 * This is the legacy version of drm_crtc_wait_one_vblank().
 */
void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    int ret;
    u64 last;

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    ret = drm_vblank_get(dev, pipe);
    if (drm_WARN(dev, ret, "vblank not available on crtc %i, ret=%i\n", pipe, ret)) {
        return;
    }

    last = drm_vblank_count(dev, pipe);

    ret = wait_event_timeout(vblank->queue, last != drm_vblank_count(dev, pipe), msecs_to_jiffies(0x64));

    drm_WARN(dev, ret == 0, "vblank wait timed out on crtc %i\n", pipe);

    drm_vblank_put(dev, pipe);
}
EXPORT_SYMBOL(drm_wait_one_vblank);

/**
 * drm_crtc_wait_one_vblank - wait for one vblank
 * @crtc: DRM crtc
 *
 * This waits for one vblank to pass on @crtc, using the irq driver interfaces.
 * It is a failure to call this when the vblank irq for @crtc is disabled, e.g.
 * due to lack of driver support or because the crtc is off.
 */
void drm_crtc_wait_one_vblank(struct drm_crtc *crtc)
{
    drm_wait_one_vblank(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_wait_one_vblank);

/**
 * drm_crtc_vblank_off - disable vblank events on a CRTC
 * @crtc: CRTC in question
 *
 * Drivers can use this function to shut down the vblank interrupt handling when
 * disabling a crtc. This function ensures that the latest vblank frame count is
 * stored so that drm_vblank_on can restore it again.
 *
 * Drivers must use this function when the hardware vblank counter can get
 * reset, e.g. when suspending or disabling the @crtc in general.
 */
void drm_crtc_vblank_off(struct drm_crtc *crtc)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    struct drm_pending_vblank_event *e, *t;
    ktime_t now;
    u64 seq;

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    /*
     * Grab event_lock early to prevent vblank work from being scheduled
     * while we're in the middle of shutting down vblank interrupts
     */
    spin_lock_irq(&dev->event_lock);

    spin_lock(&dev->vbl_lock);
    drm_dbg_vbl(dev, "crtc %d, vblank enabled %d, inmodeset %d\n", pipe, vblank->enabled, vblank->inmodeset);

    /* Avoid redundant vblank disables without previous
     * drm_crtc_vblank_on(). */
    if (drm_core_check_feature(dev, DRIVER_ATOMIC) || !vblank->inmodeset) {
        drm_vblank_disable_and_save(dev, pipe);
    }

    wake_up(&vblank->queue);

    /*
     * Prevent subsequent drm_vblank_get() from re-enabling
     * the vblank interrupt by bumping the refcount.
     */
    if (!vblank->inmodeset) {
        atomic_inc(&vblank->refcount);
        vblank->inmodeset = 1;
    }
    spin_unlock(&dev->vbl_lock);

    /* Send any queued vblank events, lest the natives grow disquiet */
    seq = drm_vblank_count_and_time(dev, pipe, &now);

    list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link)
    {
        if (e->pipe != pipe) {
            continue;
        }
        drm_dbg_core(dev,
                     "Sending premature vblank event on disable: "
                     "wanted %llu, current %llu\n",
                     e->sequence, seq);
        list_del(&e->base.link);
        drm_vblank_put(dev, pipe);
        send_vblank_event(dev, e, seq, now);
    }

    /* Cancel any leftover pending vblank work */
    drm_vblank_cancel_pending_works(vblank);

    spin_unlock_irq(&dev->event_lock);

    /* Will be reset by the modeset helpers when re-enabling the crtc by
     * calling drm_calc_timestamping_constants(). */
    vblank->hwmode.crtc_clock = 0;

    /* Wait for any vblank work that's still executing to finish */
    drm_vblank_flush_worker(vblank);
}
EXPORT_SYMBOL(drm_crtc_vblank_off);

/**
 * drm_crtc_vblank_reset - reset vblank state to off on a CRTC
 * @crtc: CRTC in question
 *
 * Drivers can use this function to reset the vblank state to off at load time.
 * Drivers should use this together with the drm_crtc_vblank_off() and
 * drm_crtc_vblank_on() functions. The difference compared to
 * drm_crtc_vblank_off() is that this function doesn't save the vblank counter
 * and hence doesn't need to call any driver hooks.
 *
 * This is useful for recovering driver state e.g. on driver load, or on resume.
 */
void drm_crtc_vblank_reset(struct drm_crtc *crtc)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    spin_lock_irq(&dev->vbl_lock);
    /*
     * Prevent subsequent drm_vblank_get() from enabling the vblank
     * interrupt by bumping the refcount.
     */
    if (!vblank->inmodeset) {
        atomic_inc(&vblank->refcount);
        vblank->inmodeset = 1;
    }
    spin_unlock_irq(&dev->vbl_lock);

    drm_WARN_ON(dev, !list_empty(&dev->vblank_event_list));
    drm_WARN_ON(dev, !list_empty(&vblank->pending_work));
}
EXPORT_SYMBOL(drm_crtc_vblank_reset);

/**
 * drm_crtc_set_max_vblank_count - configure the hw max vblank counter value
 * @crtc: CRTC in question
 * @max_vblank_count: max hardware vblank counter value
 *
 * Update the maximum hardware vblank counter value for @crtc
 * at runtime. Useful for hardware where the operation of the
 * hardware vblank counter depends on the currently active
 * display configuration.
 *
 * For example, if the hardware vblank counter does not work
 * when a specific connector is active the maximum can be set
 * to zero. And when that specific connector isn't active the
 * maximum can again be set to the appropriate non-zero value.
 *
 * If used, must be called before drm_vblank_on().
 */
void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc, u32 max_vblank_count)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    drm_WARN_ON(dev, dev->max_vblank_count);
    drm_WARN_ON(dev, !READ_ONCE(vblank->inmodeset));

    vblank->max_vblank_count = max_vblank_count;
}
EXPORT_SYMBOL(drm_crtc_set_max_vblank_count);

/**
 * drm_crtc_vblank_on - enable vblank events on a CRTC
 * @crtc: CRTC in question
 *
 * This functions restores the vblank interrupt state captured with
 * drm_crtc_vblank_off() again and is generally called when enabling @crtc. Note
 * that calls to drm_crtc_vblank_on() and drm_crtc_vblank_off() can be
 * unbalanced and so can also be unconditionally called in driver load code to
 * reflect the current hardware state of the crtc.
 */
void drm_crtc_vblank_on(struct drm_crtc *crtc)
{
    struct drm_device *dev = crtc->dev;
    unsigned int pipe = drm_crtc_index(crtc);
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    spin_lock_irq(&dev->vbl_lock);
    drm_dbg_vbl(dev, "crtc %d, vblank enabled %d, inmodeset %d\n", pipe, vblank->enabled, vblank->inmodeset);

    /* Drop our private "prevent drm_vblank_get" refcount */
    if (vblank->inmodeset) {
        atomic_dec(&vblank->refcount);
        vblank->inmodeset = 0;
    }

    drm_reset_vblank_timestamp(dev, pipe);

    /*
     * re-enable interrupts if there are users left, or the
     * user wishes vblank interrupts to be enabled all the time.
     */
    if (atomic_read(&vblank->refcount) != 0 || drm_vblank_offdelay == 0) {
        drm_WARN_ON(dev, drm_vblank_enable(dev, pipe));
    }
    spin_unlock_irq(&dev->vbl_lock);
}
EXPORT_SYMBOL(drm_crtc_vblank_on);

/**
 * drm_vblank_restore - estimate missed vblanks and update vblank count.
 * @dev: DRM device
 * @pipe: CRTC index
 *
 * Power manamement features can cause frame counter resets between vblank
 * disable and enable. Drivers can use this function in their
 * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since
 * the last &drm_crtc_funcs.disable_vblank using timestamps and update the
 * vblank counter.
 *
 * This function is the legacy version of drm_crtc_vblank_restore().
 */
void drm_vblank_restore(struct drm_device *dev, unsigned int pipe)
{
    ktime_t t_vblank;
    struct drm_vblank_crtc *vblank;
    int framedur_ns;
    u64 diff_ns;
    u32 cur_vblank, diff = 1;
    int count = DRM_TIMESTAMP_MAXRETRIES;

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    assert_spin_locked(&dev->vbl_lock);
    assert_spin_locked(&dev->vblank_time_lock);

    vblank = &dev->vblank[pipe];
    drm_WARN_ONCE(dev, drm_debug_enabled(DRM_UT_VBL) && !vblank->framedur_ns,
                  "Cannot compute missed vblanks without frame duration\n");
    framedur_ns = vblank->framedur_ns;

    do {
        cur_vblank = _get_vblank_counter(dev, pipe);
        drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);
    } while (cur_vblank != _get_vblank_counter(dev, pipe) && --count > 0);

    diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
    if (framedur_ns) {
        diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);
    }

    drm_dbg_vbl(dev, "missed %d vblanks in %lld ns, frame duration=%d ns, hw_diff=%d\n", diff, diff_ns, framedur_ns,
                cur_vblank - vblank->last);
    store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
}
EXPORT_SYMBOL(drm_vblank_restore);

/**
 * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count.
 * @crtc: CRTC in question
 *
 * Power manamement features can cause frame counter resets between vblank
 * disable and enable. Drivers can use this function in their
 * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since
 * the last &drm_crtc_funcs.disable_vblank using timestamps and update the
 * vblank counter.
 */
void drm_crtc_vblank_restore(struct drm_crtc *crtc)
{
    drm_vblank_restore(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_vblank_restore);

static void drm_legacy_vblank_pre_modeset(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    /* vblank is not initialized (IRQ not installed ?), or has been freed */
    if (!drm_dev_has_vblank(dev)) {
        return;
    }

    if (drm_WARN_ON(dev, pipe >= 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 (!vblank->inmodeset) {
        vblank->inmodeset = 0x1;
        if (drm_vblank_get(dev, pipe) == 0) {
            vblank->inmodeset |= 0x2;
        }
    }
}

static void drm_legacy_vblank_post_modeset(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

    /* vblank is not initialized (IRQ not installed ?), or has been freed */
    if (!drm_dev_has_vblank(dev)) {
        return;
    }

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return;
    }

    if (vblank->inmodeset) {
        spin_lock_irq(&dev->vbl_lock);
        drm_reset_vblank_timestamp(dev, pipe);
        spin_unlock_irq(&dev->vbl_lock);

        if (vblank->inmodeset & 0x2) {
            drm_vblank_put(dev, pipe);
        }

        vblank->inmodeset = 0;
    }
}

int drm_legacy_modeset_ctl_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_modeset_ctl *modeset = data;
    unsigned int pipe;

    /* If drm_vblank_init() hasn't been called yet, just no-op */
    if (!drm_dev_has_vblank(dev)) {
        return 0;
    }

    /* KMS drivers handle this internally */
    if (!drm_core_check_feature(dev, DRIVER_LEGACY)) {
        return 0;
    }

    pipe = modeset->crtc;
    if (pipe >= dev->num_crtcs) {
        return -EINVAL;
    }

    switch (modeset->cmd) {
        case _DRM_PRE_MODESET:
            drm_legacy_vblank_pre_modeset(dev, pipe);
            break;
        case _DRM_POST_MODESET:
            drm_legacy_vblank_post_modeset(dev, pipe);
            break;
        default:
            return -EINVAL;
    }

    return 0;
}

static int drm_queue_vblank_event(struct drm_device *dev, unsigned int pipe, u64 req_seq,
                                  union drm_wait_vblank *vblwait, struct drm_file *file_priv)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    struct drm_pending_vblank_event *e;
    ktime_t now;
    u64 seq;
    int ret;

    e = kzalloc(sizeof(*e), GFP_KERNEL);
    if (e == NULL) {
        ret = -ENOMEM;
        goto err_put;
    }

    e->pipe = pipe;
    e->event.base.type = DRM_EVENT_VBLANK;
    e->event.base.length = sizeof(e->event.vbl);
    e->event.vbl.user_data = vblwait->request.signal;
    e->event.vbl.crtc_id = 0;
    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
        struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);

        if (crtc) {
            e->event.vbl.crtc_id = crtc->base.id;
        }
    }

    spin_lock_irq(&dev->event_lock);

    /*
     * drm_crtc_vblank_off() might have been called after we called
     * drm_vblank_get(). drm_crtc_vblank_off() holds event_lock around the
     * vblank disable, so no need for further locking.  The reference from
     * drm_vblank_get() protects against vblank disable from another source.
     */
    if (!READ_ONCE(vblank->enabled)) {
        ret = -EINVAL;
        goto err_unlock;
    }

    ret = drm_event_reserve_init_locked(dev, file_priv, &e->base, &e->event.base);
    if (ret) {
        goto err_unlock;
    }

    seq = drm_vblank_count_and_time(dev, pipe, &now);

    drm_dbg_core(dev, "event on vblank count %llu, current %llu, crtc %u\n", req_seq, seq, pipe);

    trace_drm_vblank_event_queued(file_priv, pipe, req_seq);

    e->sequence = req_seq;
    if (drm_vblank_passed(seq, req_seq)) {
        drm_vblank_put(dev, pipe);
        send_vblank_event(dev, e, seq, now);
        vblwait->reply.sequence = seq;
    } else {
        /* drm_handle_vblank_events will call drm_vblank_put */
        list_add_tail(&e->base.link, &dev->vblank_event_list);
        vblwait->reply.sequence = req_seq;
    }

    spin_unlock_irq(&dev->event_lock);

    return 0;

err_unlock:
    spin_unlock_irq(&dev->event_lock);
    kfree(e);
err_put:
    drm_vblank_put(dev, pipe);
    return ret;
}

static bool drm_wait_vblank_is_query(union drm_wait_vblank *vblwait)
{
    if (vblwait->request.sequence) {
        return false;
    }

    return _DRM_VBLANK_RELATIVE ==
           (vblwait->request.type & (_DRM_VBLANK_TYPES_MASK | _DRM_VBLANK_EVENT | _DRM_VBLANK_NEXTONMISS));
}

/*
 * Widen a 32-bit param to 64-bits.
 *
 * \param narrow 32-bit value (missing upper 32 bits)
 * \param near 64-bit value that should be 'close' to near
 *
 * This function returns a 64-bit value using the lower 32-bits from
 * 'narrow' and constructing the upper 32-bits so that the result is
 * as close as possible to 'near'.
 */

static u64 widen_32_to_64(u32 narrow, u64 near)
{
    return near + (s32)(narrow - near);
}

static void drm_wait_vblank_reply(struct drm_device *dev, unsigned int pipe, struct drm_wait_vblank_reply *reply)
{
    ktime_t now;
    struct timespec64 ts;

    /*
     * drm_wait_vblank_reply is a UAPI structure that uses 'long'
     * to store the seconds. This is safe as we always use monotonic
     * timestamps since linux-4.15.
     */
    reply->sequence = drm_vblank_count_and_time(dev, pipe, &now);
    ts = ktime_to_timespec64(now);
    reply->tval_sec = (u32)ts.tv_sec;
    reply->tval_usec = ts.tv_nsec / 0x3e8;
}

int drm_wait_vblank_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_crtc *crtc;
    struct drm_vblank_crtc *vblank;
    union drm_wait_vblank *vblwait = data;
    int ret;
    u64 req_seq, seq;
    unsigned int pipe_index;
    unsigned int flags, pipe, high_pipe;

    if (!dev->irq_enabled) {
        return -EOPNOTSUPP;
    }

    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_dbg_core(dev, "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_pipe = (vblwait->request.type & _DRM_VBLANK_HIGH_CRTC_MASK);
    if (high_pipe) {
        pipe_index = high_pipe >> _DRM_VBLANK_HIGH_CRTC_SHIFT;
    } else {
        pipe_index = flags & _DRM_VBLANK_SECONDARY ? 1 : 0;
    }

    /* Convert lease-relative crtc index into global crtc index */
    if (drm_core_check_feature(dev, DRIVER_MODESET)) {
        pipe = 0;
        drm_for_each_crtc(crtc, dev)
        {
            if (drm_lease_held(file_priv, crtc->base.id)) {
                if (pipe_index == 0) {
                    break;
                }
                pipe_index--;
            }
            pipe++;
        }
    } else {
        pipe = pipe_index;
    }

    if (pipe >= dev->num_crtcs) {
        return -EINVAL;
    }

    vblank = &dev->vblank[pipe];

    /* If the counter is currently enabled and accurate, short-circuit
     * queries to return the cached timestamp of the last vblank.
     */
    if (dev->vblank_disable_immediate && drm_wait_vblank_is_query(vblwait) && READ_ONCE(vblank->enabled)) {
        drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
        return 0;
    }

    ret = drm_vblank_get(dev, pipe);
    if (ret) {
        drm_dbg_core(dev, "crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
        return ret;
    }
    seq = drm_vblank_count(dev, pipe);

    switch (vblwait->request.type & _DRM_VBLANK_TYPES_MASK) {
        case _DRM_VBLANK_RELATIVE:
            req_seq = seq + vblwait->request.sequence;
            vblwait->request.sequence = req_seq;
            vblwait->request.type &= ~_DRM_VBLANK_RELATIVE;
            break;
        case _DRM_VBLANK_ABSOLUTE:
            req_seq = widen_32_to_64(vblwait->request.sequence, seq);
            break;
        default:
            ret = -EINVAL;
            goto done;
    }

    if ((flags & _DRM_VBLANK_NEXTONMISS) && drm_vblank_passed(seq, req_seq)) {
        req_seq = seq + 1;
        vblwait->request.type &= ~_DRM_VBLANK_NEXTONMISS;
        vblwait->request.sequence = req_seq;
    }

    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, pipe, req_seq, vblwait, file_priv);
    }

    if (req_seq != seq) {
        int wait;

        drm_dbg_core(dev, "waiting on vblank count %llu, crtc %u\n", req_seq, pipe);
        wait = wait_event_interruptible_timeout(
            vblank->queue, drm_vblank_passed(drm_vblank_count(dev, pipe), req_seq) || !READ_ONCE(vblank->enabled),
            msecs_to_jiffies(0xbb8));

        switch (wait) {
            case 0:
                /* timeout */
                ret = -EBUSY;
                break;
            case -ERESTARTSYS:
                /* interrupted by signal */
                ret = -EINTR;
                break;
            default:
                ret = 0;
                break;
        }
    }

    if (ret != -EINTR) {
        drm_wait_vblank_reply(dev, pipe, &vblwait->reply);

        drm_dbg_core(dev, "crtc %d returning %u to client\n", pipe, vblwait->reply.sequence);
    } else {
        drm_dbg_core(dev, "crtc %d vblank wait interrupted by signal\n", pipe);
    }

done:
    drm_vblank_put(dev, pipe);
    return ret;
}

static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
{
    struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
    bool high_prec = false;
    struct drm_pending_vblank_event *e, *t;
    ktime_t now;
    u64 seq;

    assert_spin_locked(&dev->event_lock);

    seq = drm_vblank_count_and_time(dev, pipe, &now);

    list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link)
    {
        if (e->pipe != pipe) {
            continue;
        }
        if (!drm_vblank_passed(seq, e->sequence)) {
            continue;
        }

        drm_dbg_core(dev, "vblank event on %llu, current %llu\n", e->sequence, seq);

        list_del(&e->base.link);
        drm_vblank_put(dev, pipe);
        send_vblank_event(dev, e, seq, now);
    }

    if (crtc && crtc->funcs->get_vblank_timestamp) {
        high_prec = true;
    }

    trace_drm_vblank_event(pipe, seq, now, high_prec);
}

/**
 * drm_handle_vblank - handle a vblank event
 * @dev: DRM device
 * @pipe: index of 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.
 *
 * This is the legacy version of drm_crtc_handle_vblank().
 */
bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
{
    struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
    unsigned long irqflags;
    bool disable_irq;

    if (drm_WARN_ON_ONCE(dev, !drm_dev_has_vblank(dev))) {
        return false;
    }

    if (drm_WARN_ON(dev, pipe >= dev->num_crtcs)) {
        return false;
    }

    spin_lock_irqsave(&dev->event_lock, irqflags);

    /* Need timestamp lock to prevent concurrent execution with
     * vblank enable/disable, as this would cause inconsistent
     * or corrupted timestamps and vblank counts.
     */
    spin_lock(&dev->vblank_time_lock);

    /* Vblank irq handling disabled. Nothing to do. */
    if (!vblank->enabled) {
        spin_unlock(&dev->vblank_time_lock);
        spin_unlock_irqrestore(&dev->event_lock, irqflags);
        return false;
    }

    drm_update_vblank_count(dev, pipe, true);

    spin_unlock(&dev->vblank_time_lock);

    wake_up(&vblank->queue);

    /* With instant-off, we defer disabling the interrupt until after
     * we finish processing the following vblank after all events have
     * been signaled. The disable has to be last (after
     * drm_handle_vblank_events) so that the timestamp is always accurate.
     */
    disable_irq = (dev->vblank_disable_immediate && drm_vblank_offdelay > 0 && !atomic_read(&vblank->refcount));

    drm_handle_vblank_events(dev, pipe);
    drm_handle_vblank_works(vblank);

    spin_unlock_irqrestore(&dev->event_lock, irqflags);

    if (disable_irq) {
        vblank_disable_fn(&vblank->disable_timer);
    }

    return true;
}
EXPORT_SYMBOL(drm_handle_vblank);

/**
 * drm_crtc_handle_vblank - handle a vblank event
 * @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.
 *
 * This is the native KMS version of drm_handle_vblank().
 *
 * Note that for a given vblank counter value drm_crtc_handle_vblank()
 * and drm_crtc_vblank_count() or drm_crtc_vblank_count_and_time()
 * provide a barrier: Any writes done before calling
 * drm_crtc_handle_vblank() will be visible to callers of the later
 * functions, iff the vblank count is the same or a later one.
 *
 * See also &drm_vblank_crtc.count.
 *
 * Returns:
 * True if the event was successfully handled, false on failure.
 */
bool drm_crtc_handle_vblank(struct drm_crtc *crtc)
{
    return drm_handle_vblank(crtc->dev, drm_crtc_index(crtc));
}
EXPORT_SYMBOL(drm_crtc_handle_vblank);

/*
 * Get crtc VBLANK count.
 *
 * \param dev DRM device
 * \param data user arguement, pointing to a drm_crtc_get_sequence structure.
 * \param file_priv drm file private for the user's open file descriptor
 */

int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_crtc *crtc;
    struct drm_vblank_crtc *vblank;
    int pipe;
    struct drm_crtc_get_sequence *get_seq = data;
    ktime_t now;
    bool vblank_enabled;
    int ret;

    if (!drm_core_check_feature(dev, DRIVER_MODESET)) {
        return -EOPNOTSUPP;
    }

    if (!dev->irq_enabled) {
        return -EOPNOTSUPP;
    }

    crtc = drm_crtc_find(dev, file_priv, get_seq->crtc_id);
    if (!crtc) {
        return -ENOENT;
    }

    pipe = drm_crtc_index(crtc);

    vblank = &dev->vblank[pipe];
    vblank_enabled = dev->vblank_disable_immediate && READ_ONCE(vblank->enabled);
    if (!vblank_enabled) {
        ret = drm_crtc_vblank_get(crtc);
        if (ret) {
            drm_dbg_core(dev, "crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
            return ret;
        }
    }
    drm_modeset_lock(&crtc->mutex, NULL);
    if (crtc->state) {
        get_seq->active = crtc->state->enable;
    } else {
        get_seq->active = crtc->enabled;
    }
    drm_modeset_unlock(&crtc->mutex);
    get_seq->sequence = drm_vblank_count_and_time(dev, pipe, &now);
    get_seq->sequence_ns = ktime_to_ns(now);
    if (!vblank_enabled) {
        drm_crtc_vblank_put(crtc);
    }
    return 0;
}

/*
 * Queue a event for VBLANK sequence
 *
 * \param dev DRM device
 * \param data user arguement, pointing to a drm_crtc_queue_sequence structure.
 * \param file_priv drm file private for the user's open file descriptor
 */

int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv)
{
    struct drm_crtc *crtc;
    struct drm_vblank_crtc *vblank;
    int pipe;
    struct drm_crtc_queue_sequence *queue_seq = data;
    ktime_t now;
    struct drm_pending_vblank_event *e;
    u32 flags;
    u64 seq;
    u64 req_seq;
    int ret;

    if (!drm_core_check_feature(dev, DRIVER_MODESET)) {
        return -EOPNOTSUPP;
    }

    if (!dev->irq_enabled) {
        return -EOPNOTSUPP;
    }

    crtc = drm_crtc_find(dev, file_priv, queue_seq->crtc_id);
    if (!crtc) {
        return -ENOENT;
    }

    flags = queue_seq->flags;
    /* Check valid flag bits */
    if (flags & ~(DRM_CRTC_SEQUENCE_RELATIVE | DRM_CRTC_SEQUENCE_NEXT_ON_MISS)) {
        return -EINVAL;
    }

    pipe = drm_crtc_index(crtc);

    vblank = &dev->vblank[pipe];

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

    ret = drm_crtc_vblank_get(crtc);
    if (ret) {
        drm_dbg_core(dev, "crtc %d failed to acquire vblank counter, %d\n", pipe, ret);
        goto err_free;
    }

    seq = drm_vblank_count_and_time(dev, pipe, &now);
    req_seq = queue_seq->sequence;

    if (flags & DRM_CRTC_SEQUENCE_RELATIVE) {
        req_seq += seq;
    }

    if ((flags & DRM_CRTC_SEQUENCE_NEXT_ON_MISS) && drm_vblank_passed(seq, req_seq)) {
        req_seq = seq + 1;
    }

    e->pipe = pipe;
    e->event.base.type = DRM_EVENT_CRTC_SEQUENCE;
    e->event.base.length = sizeof(e->event.seq);
    e->event.seq.user_data = queue_seq->user_data;

    spin_lock_irq(&dev->event_lock);

    /*
     * drm_crtc_vblank_off() might have been called after we called
     * drm_crtc_vblank_get(). drm_crtc_vblank_off() holds event_lock around the
     * vblank disable, so no need for further locking.  The reference from
     * drm_crtc_vblank_get() protects against vblank disable from another source.
     */
    if (!READ_ONCE(vblank->enabled)) {
        ret = -EINVAL;
        goto err_unlock;
    }

    ret = drm_event_reserve_init_locked(dev, file_priv, &e->base, &e->event.base);
    if (ret) {
        goto err_unlock;
    }

    e->sequence = req_seq;

    if (drm_vblank_passed(seq, req_seq)) {
        drm_crtc_vblank_put(crtc);
        send_vblank_event(dev, e, seq, now);
        queue_seq->sequence = seq;
    } else {
        /* drm_handle_vblank_events will call drm_vblank_put */
        list_add_tail(&e->base.link, &dev->vblank_event_list);
        queue_seq->sequence = req_seq;
    }

    spin_unlock_irq(&dev->event_lock);
    return 0;

err_unlock:
    spin_unlock_irq(&dev->event_lock);
    drm_crtc_vblank_put(crtc);
err_free:
    kfree(e);
    return ret;
}