Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2178 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
new file mode 100644
index 000000000..2ff31717a
--- /dev/null
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -0,0 +1,2178 @@
+/*
+ * 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
+ *                |                                        |   ("scan 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 usable 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);
+	}
+#ifdef CONFIG_DRM_LEGACY
+	else if (dev->driver->get_vblank_counter) {
+		return dev->driver->get_vblank_counter(dev, pipe);
+	}
+#endif
+
+	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);
+	}
+#ifdef CONFIG_DRM_LEGACY
+	else {
+		dev->driver->disable_vblank(dev, pipe);
+	}
+#endif
+}
+
+/*
+ * 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 * 1000000, dotclock);
+		framedur_ns = div_u64((u64) frame_size * 1000000, dotclock);
+
+		/*
+		 * Fields of interlaced scanout modes are only half a frame duration.
+		 */
+		if (mode->flags & DRM_MODE_FLAG_INTERLACE)
+			framedur_ns /= 2;
+	} 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;
+	drm_mode_copy(&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:
+ *
+ * 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 / 1000, *max_error / 1000, 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 / 1000,
+		    (u64)ts_vblank_time.tv_sec, ts_vblank_time.tv_nsec / 1000,
+		    duration_ns / 1000, 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:
+ *
+ * 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 = drm_crtc_from_index(dev, pipe);
+
+		ret = crtc->funcs->get_vblank_timestamp(crtc, &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, if 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, if 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 / 1000;
+		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);
+	}
+#ifdef CONFIG_DRM_LEGACY
+	else if (dev->driver->enable_vblank) {
+		return dev->driver->enable_vblank(dev, pipe);
+	}
+#endif
+
+	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)/1000));
+	}
+}
+
+/**
+ * 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(100));
+
+	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);
+
+static 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;
+	u32 max_vblank_count = drm_max_vblank_count(dev, pipe);
+
+	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);
+	vblank->last = (cur_vblank - diff) & max_vblank_count;
+}
+
+/**
+ * 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.
+ *
+ * Note that drivers must have race-free high-precision timestamping support,
+ * i.e.  &drm_crtc_funcs.get_vblank_timestamp must be hooked up and
+ * &drm_driver.vblank_disable_immediate must be set to indicate the
+ * time-stamping functions are race-free against vblank hardware counter
+ * increments.
+ */
+void drm_crtc_vblank_restore(struct drm_crtc *crtc)
+{
+	WARN_ON_ONCE(!crtc->funcs->get_vblank_timestamp);
+	WARN_ON_ONCE(!crtc->dev->vblank_disable_immediate);
+
+	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 / 1000;
+}
+
+static bool drm_wait_vblank_supported(struct drm_device *dev)
+{
+#if IS_ENABLED(CONFIG_DRM_LEGACY)
+	if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)))
+		return dev->irq_enabled;
+#endif
+	return drm_dev_has_vblank(dev);
+}
+
+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 (!drm_wait_vblank_supported(dev))
+		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(3000));
+
+		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, if 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 argument, 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 (!drm_dev_has_vblank(dev))
+		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 argument, 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 (!drm_dev_has_vblank(dev))
+		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;
+}
+