/* * drm_irq.c IRQ and vblank support * * \author Rickard E. (Rik) Faith * \author Gareth Hughes */ /* * Created: Fri Mar 19 14:30:16 1999 by faith@valinux.com * * Copyright 1999, 2000 Precision Insight, Inc., Cedar Park, Texas. * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. * All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. */ #include //#include "drm_trace.h" #include "drm_internal.h" #include /* For task queue support */ #include #include #include ktime_t ktime_get(void); static inline ktime_t ktime_get_real(void) { return ktime_get(); } static inline ktime_t ktime_mono_to_real(ktime_t mono) { return mono; } irqreturn_t device_irq_handler(struct drm_device *dev) { return dev->driver->irq_handler(0, dev); } /* Access macro for slots in vblank timestamp ringbuffer. */ #define vblanktimestamp(dev, pipe, count) \ ((dev)->vblank[pipe].time[(count) % DRM_VBLANKTIME_RBSIZE]) /* Retry timestamp calculation up to 3 times to satisfy * drm_timestamp_precision before giving up. */ #define DRM_TIMESTAMP_MAXRETRIES 3 /* Threshold in nanoseconds for detection of redundant * vblank irq in drm_handle_vblank(). 1 msec should be ok. */ #define DRM_REDUNDANT_VBLIRQ_THRESH_NS 1000000 static bool drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, struct timeval *tvblank, unsigned flags); static unsigned int drm_timestamp_precision = 20; /* Default to 20 usecs. */ /* * Default to use monotonic timestamps for wait-for-vblank and page-flip * complete events. */ unsigned int drm_timestamp_monotonic = 1; 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_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600); static void store_vblank(struct drm_device *dev, unsigned int pipe, u32 vblank_count_inc, struct timeval *t_vblank, u32 last) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; u32 tslot; assert_spin_locked(&dev->vblank_time_lock); vblank->last = last; /* All writers hold the spinlock, but readers are serialized by * the latching of vblank->count below. */ tslot = vblank->count + vblank_count_inc; vblanktimestamp(dev, pipe, tslot) = *t_vblank; /* * vblank timestamp updates are protected on the write side with * vblank_time_lock, but on the read side done locklessly using a * sequence-lock on the vblank counter. Ensure correct ordering using * memory barrriers. We need the barrier both before and also after the * counter update to synchronize with the next timestamp write. * The read-side barriers for this are in drm_vblank_count_and_time. */ smp_wmb(); vblank->count += vblank_count_inc; smp_wmb(); } /** * drm_reset_vblank_timestamp - reset the last timestamp to the last vblank * @dev: DRM device * @pipe: index of CRTC for which to reset the timestamp * * Reset the stored timestamp for the current vblank count to correspond * to the last vblank occurred. * * Only to be called from drm_vblank_on(). * * Note: caller must hold dev->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; struct timeval 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 = dev->driver->get_vblank_counter(dev, pipe); rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, 0); } while (cur_vblank != dev->driver->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 = (struct timeval) {0, 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); } /** * drm_update_vblank_count - update the master vblank counter * @dev: DRM device * @pipe: counter to update * * 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 dev->vbl_lock since this reads & writes * device vblank fields. */ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, unsigned long flags) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; u32 cur_vblank, diff; bool rc; struct timeval t_vblank; int count = DRM_TIMESTAMP_MAXRETRIES; int framedur_ns = vblank->framedur_ns; /* * 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 = dev->driver->get_vblank_counter(dev, pipe); rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, flags); } while (cur_vblank != dev->driver->get_vblank_counter(dev, pipe) && --count > 0); if (dev->max_vblank_count != 0) { /* trust the hw counter when it's around */ diff = (cur_vblank - vblank->last) & dev->max_vblank_count; } else if (rc && framedur_ns) { const struct timeval *t_old; u64 diff_ns; t_old = &vblanktimestamp(dev, pipe, vblank->count); diff_ns = timeval_to_ns(&t_vblank) - timeval_to_ns(t_old); /* * Figure out how many vblanks we've missed based * on the difference in the timestamps and the * frame/field duration. */ diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns); if (diff == 0 && flags & DRM_CALLED_FROM_VBLIRQ) DRM_DEBUG_VBL("crtc %u: Redundant vblirq ignored." " diff_ns = %lld, framedur_ns = %d)\n", pipe, (long long) diff_ns, framedur_ns); } else { /* some kind of default for drivers w/o accurate vbl timestamping */ diff = (flags & DRM_CALLED_FROM_VBLIRQ) != 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_DEBUG_VBL("clamping vblank bump to 1 on crtc %u: diffr=%u" " due to pre-modeset.\n", pipe, diff); diff = 1; } /* * FIMXE: Need to replace this hack with proper seqlocks. * * Restrict the bump of the software vblank counter to a safe maximum * value of +1 whenever there is the possibility that concurrent readers * of vblank timestamps could be active at the moment, as the current * implementation of the timestamp caching and updating is not safe * against concurrent readers for calls to store_vblank() with a bump * of anything but +1. A bump != 1 would very likely return corrupted * timestamps to userspace, because the same slot in the cache could * be concurrently written by store_vblank() and read by one of those * readers without the read-retry logic detecting the collision. * * Concurrent readers can exist when we are called from the * drm_vblank_off() or drm_vblank_on() functions and other non-vblank- * irq callers. However, all those calls to us are happening with the * vbl_lock locked to prevent drm_vblank_get(), so the vblank refcount * can't increase while we are executing. Therefore a zero refcount at * this point is safe for arbitrary counter bumps if we are called * outside vblank irq, a non-zero count is not 100% safe. Unfortunately * we must also accept a refcount of 1, as whenever we are called from * drm_vblank_get() -> drm_vblank_enable() the refcount will be 1 and * we must let that one pass through in order to not lose vblank counts * during vblank irq off - which would completely defeat the whole * point of this routine. * * Whenever we are called from vblank irq, we have to assume concurrent * readers exist or can show up any time during our execution, even if * the refcount is currently zero, as vblank irqs are usually only * enabled due to the presence of readers, and because when we are called * from vblank irq we can't hold the vbl_lock to protect us from sudden * bumps in vblank refcount. Therefore also restrict bumps to +1 when * called from vblank irq. */ if ((diff > 1) && (atomic_read(&vblank->refcount) > 1 || (flags & DRM_CALLED_FROM_VBLIRQ))) { DRM_DEBUG_VBL("clamping vblank bump to 1 on crtc %u: diffr=%u " "refcount %u, vblirq %u\n", pipe, diff, atomic_read(&vblank->refcount), (flags & DRM_CALLED_FROM_VBLIRQ) != 0); diff = 1; } DRM_DEBUG_VBL("updating vblank count on crtc %u:" " current=%u, diff=%u, hw=%u hw_last=%u\n", pipe, vblank->count, diff, cur_vblank, vblank->last); if (diff == 0) { WARN_ON_ONCE(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 && (flags & DRM_CALLED_FROM_VBLIRQ) == 0) t_vblank = (struct timeval) {0, 0}; store_vblank(dev, pipe, diff, &t_vblank, cur_vblank); } /* * Disable vblank irq's on crtc, make sure that last vblank count * of hardware and corresponding consistent software vblank counter * are preserved, even if there are any spurious vblank irq's after * disable. */ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; unsigned long irqflags; /* 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); /* * Only disable vblank interrupts if they're enabled. This avoids * calling the ->disable_vblank() operation in atomic context with the * hardware potentially runtime suspended. */ if (vblank->enabled) { dev->driver->disable_vblank(dev, pipe); vblank->enabled = false; } /* * Always 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_vblank_on() and drm_vblank_off(). */ drm_update_vblank_count(dev, pipe, 0); spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags); } static void vblank_disable_fn(unsigned long arg) { struct drm_vblank_crtc *vblank = (void *)arg; struct drm_device *dev = vblank->dev; unsigned int pipe = vblank->pipe; unsigned long irqflags; if (!dev->vblank_disable_allowed) return; spin_lock_irqsave(&dev->vbl_lock, irqflags); if (atomic_read(&vblank->refcount) == 0 && vblank->enabled) { DRM_DEBUG("disabling vblank on crtc %u\n", pipe); vblank_disable_and_save(dev, pipe); } spin_unlock_irqrestore(&dev->vbl_lock, irqflags); } /** * drm_vblank_cleanup - cleanup vblank support * @dev: DRM device * * This function cleans up any resources allocated in drm_vblank_init. */ void drm_vblank_cleanup(struct drm_device *dev) { unsigned int pipe; /* Bail if the driver didn't call drm_vblank_init() */ if (dev->num_crtcs == 0) return; for (pipe = 0; pipe < dev->num_crtcs; pipe++) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; WARN_ON(vblank->enabled && drm_core_check_feature(dev, DRIVER_MODESET)); del_timer_sync(&vblank->disable_timer); } kfree(dev->vblank); dev->num_crtcs = 0; } EXPORT_SYMBOL(drm_vblank_cleanup); /** * 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. * * 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 = -ENOMEM; unsigned int i; spin_lock_init(&dev->vbl_lock); spin_lock_init(&dev->vblank_time_lock); dev->num_crtcs = num_crtcs; dev->vblank = kcalloc(num_crtcs, sizeof(*dev->vblank), GFP_KERNEL); if (!dev->vblank) goto err; 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); setup_timer(&vblank->disable_timer, vblank_disable_fn, (unsigned long)vblank); } DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n"); /* Driver specific high-precision vblank timestamping supported? */ if (dev->driver->get_vblank_timestamp) DRM_INFO("Driver supports precise vblank timestamp query.\n"); else DRM_INFO("No driver support for vblank timestamp query.\n"); /* Must have precise timestamping for reliable vblank instant disable */ if (dev->vblank_disable_immediate && !dev->driver->get_vblank_timestamp) { dev->vblank_disable_immediate = false; DRM_INFO("Setting vblank_disable_immediate to false because " "get_vblank_timestamp == NULL\n"); } dev->vblank_disable_allowed = false; return 0; err: dev->num_crtcs = 0; return ret; } EXPORT_SYMBOL(drm_vblank_init); /** * drm_irq_install - install IRQ handler * @dev: DRM device * @irq: IRQ number to install the handler for * * Initializes the IRQ related data. Installs the handler, calling the driver * irq_preinstall() and irq_postinstall() functions before and after the * installation. * * This is the simplified helper interface provided for drivers with no special * needs. Drivers which need to install interrupt handlers for multiple * interrupts must instead set drm_device->irq_enabled to signal the DRM core * that vblank interrupts are available. * * Returns: * Zero on success or a negative error code on failure. */ int drm_irq_install(struct drm_device *dev, int irq) { int ret; unsigned long sh_flags = 0; if (!drm_core_check_feature(dev, DRIVER_HAVE_IRQ)) return -EINVAL; if (irq == 0) return -EINVAL; /* Driver must have been initialized */ if (!dev->dev_private) return -EINVAL; if (dev->irq_enabled) return -EBUSY; dev->irq_enabled = true; DRM_DEBUG("irq=%d\n", irq); /* Before installing handler */ if (dev->driver->irq_preinstall) dev->driver->irq_preinstall(dev); ret = !AttachIntHandler(irq, device_irq_handler, (u32)dev); /* After installing handler */ if (dev->driver->irq_postinstall) ret = dev->driver->irq_postinstall(dev); if (ret < 0) { dev->irq_enabled = false; } else { dev->irq = irq; } u16 cmd = PciRead16(dev->pdev->busnr, dev->pdev->devfn, 4); cmd&= ~(1<<10); PciWrite16(dev->pdev->busnr, dev->pdev->devfn, 4, cmd); return ret; } EXPORT_SYMBOL(drm_irq_install); /** * 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_calc_vbltimestamp_from_scanoutpos(). They are * derived from CRTC's true scanout timing, so they take * things like panel scaling or other adjustments into account. */ 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 (!dev->num_crtcs) return; if (WARN_ON(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_ERROR("crtc %u: Can't calculate constants, dotclock = 0!\n", crtc->base.id); vblank->linedur_ns = linedur_ns; vblank->framedur_ns = framedur_ns; DRM_DEBUG("crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n", crtc->base.id, mode->crtc_htotal, mode->crtc_vtotal, mode->crtc_vdisplay); DRM_DEBUG("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_calc_vbltimestamp_from_scanoutpos - precise vblank timestamp helper * @dev: DRM device * @pipe: index of 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 struct timeval which should receive the timestamp * @flags: Flags to pass to driver: * 0 = Default, * DRM_CALLED_FROM_VBLIRQ = If function is called from vbl IRQ handler * @mode: mode which defines the scanout timings * * Implements calculation of exact vblank timestamps from given drm_display_mode * timings and current video scanout position of a CRTC. This can be called from * within get_vblank_timestamp() implementation of a kms driver to implement the * actual timestamping. * * Should return timestamps conforming to the OML_sync_control OpenML * extension specification. The timestamp corresponds to the end of * the vblank interval, aka start of scanout of topmost-leftmost display * pixel in the following video frame. * * Requires support for optional dev->driver->get_scanout_position() * in kms driver, plus a bit of setup code to provide a drm_display_mode * that corresponds to the true scanout timing. * * The current implementation only handles standard video modes. It * returns as no operation if a doublescan or interlaced video mode is * active. Higher level code is expected to handle this. * * Returns: * Negative value on error, failure or if not supported in current * video mode: * * -EINVAL - Invalid CRTC. * -EAGAIN - Temporary unavailable, e.g., called before initial modeset. * -ENOTSUPP - Function not supported in current display mode. * -EIO - Failed, e.g., due to failed scanout position query. * * Returns or'ed positive status flags on success: * * DRM_VBLANKTIME_SCANOUTPOS_METHOD - Signal this method used for timestamping. * DRM_VBLANKTIME_INVBL - Timestamp taken while scanout was in vblank interval. * */ int drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, unsigned int pipe, int *max_error, struct timeval *vblank_time, unsigned flags, const struct drm_display_mode *mode) { struct timeval tv_etime; ktime_t stime, etime; unsigned int vbl_status; int ret = DRM_VBLANKTIME_SCANOUTPOS_METHOD; int vpos, hpos, i; int delta_ns, duration_ns; if (pipe >= dev->num_crtcs) { DRM_ERROR("Invalid crtc %u\n", pipe); return -EINVAL; } /* Scanout position query not supported? Should not happen. */ if (!dev->driver->get_scanout_position) { DRM_ERROR("Called from driver w/o get_scanout_position()!?\n"); return -EIO; } /* If mode timing undefined, just return as no-op: * Happens during initial modesetting of a crtc. */ if (mode->crtc_clock == 0) { DRM_DEBUG("crtc %u: Noop due to uninitialized mode.\n", pipe); return -EAGAIN; } /* Get current scanout position with system timestamp. * Repeat query up to DRM_TIMESTAMP_MAXRETRIES times * if single query takes longer than max_error nanoseconds. * * This guarantees a tight bound on maximum error if * code gets preempted or delayed for some reason. */ for (i = 0; i < DRM_TIMESTAMP_MAXRETRIES; i++) { /* * Get vertical and horizontal scanout position vpos, hpos, * and bounding timestamps stime, etime, pre/post query. */ vbl_status = dev->driver->get_scanout_position(dev, pipe, flags, &vpos, &hpos, &stime, &etime, mode); /* Return as no-op if scanout query unsupported or failed. */ if (!(vbl_status & DRM_SCANOUTPOS_VALID)) { DRM_DEBUG("crtc %u : scanoutpos query failed [0x%x].\n", pipe, vbl_status); return -EIO; } /* 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_DEBUG("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; /* Check if in vblank area: * vpos is >=0 in video scanout area, but negative * within vblank area, counting down the number of lines until * start of scanout. */ if (vbl_status & DRM_SCANOUTPOS_IN_VBLANK) ret |= DRM_VBLANKTIME_IN_VBLANK; /* 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); if (!drm_timestamp_monotonic) etime = ktime_mono_to_real(etime); /* save this only for debugging purposes */ tv_etime = ktime_to_timeval(etime); /* Subtract time delta from raw timestamp to get final * vblank_time timestamp for end of vblank. */ if (delta_ns < 0) etime = ktime_add_ns(etime, -delta_ns); else etime = ktime_sub_ns(etime, delta_ns); *vblank_time = ktime_to_timeval(etime); DRM_DEBUG_VBL("crtc %u : v 0x%x p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n", pipe, vbl_status, hpos, vpos, (long)tv_etime.tv_sec, (long)tv_etime.tv_usec, (long)vblank_time->tv_sec, (long)vblank_time->tv_usec, duration_ns/1000, i); return ret; } EXPORT_SYMBOL(drm_calc_vbltimestamp_from_scanoutpos); static struct timeval get_drm_timestamp(void) { ktime_t now; now = drm_timestamp_monotonic ? ktime_get() : ktime_get_real(); return ktime_to_timeval(now); } /** * 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 struct timeval which should receive the timestamp * @flags: Flags to pass to driver: * 0 = Default, * DRM_CALLED_FROM_VBLIRQ = If function is called from vbl IRQ handler * * Fetches the system timestamp corresponding to the time of the most recent * vblank interval on specified CRTC. May call into kms-driver to * compute the timestamp with a high-precision GPU specific method. * * Returns zero if timestamp originates from uncorrected do_gettimeofday() * call, i.e., it isn't very precisely locked to the true vblank. * * Returns: * True if timestamp is considered to be very precise, false otherwise. */ static bool drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe, struct timeval *tvblank, unsigned flags) { int ret; /* Define requested maximum error on timestamps (nanoseconds). */ int max_error = (int) drm_timestamp_precision * 1000; /* Query driver if possible and precision timestamping enabled. */ if (dev->driver->get_vblank_timestamp && (max_error > 0)) { ret = dev->driver->get_vblank_timestamp(dev, pipe, &max_error, tvblank, flags); if (ret > 0) return true; } /* GPU high precision timestamp query unsupported or failed. * Return current monotonic/gettimeofday timestamp as best estimate. */ *tvblank = get_drm_timestamp(); return false; } /** * drm_vblank_count - retrieve "cooked" vblank counter value * @dev: DRM device * @pipe: index of CRTC for which to retrieve the counter * * 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. * * This is the legacy version of drm_crtc_vblank_count(). * * Returns: * The software vblank counter. */ u32 drm_vblank_count(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; if (WARN_ON(pipe >= dev->num_crtcs)) return 0; return vblank->count; } EXPORT_SYMBOL(drm_vblank_count); /** * 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. * * This is the native KMS version of drm_vblank_count(). * * Returns: * The software vblank counter. */ u32 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 struct timeval to receive the vblank timestamp. * * Fetches the "cooked" vblank count value that represents the number of * vblank events since the system was booted, including lost events due to * modesetting activity. Returns corresponding system timestamp of the time * of the vblank interval that corresponds to the current vblank counter value. * * This is the legacy version of drm_crtc_vblank_count_and_time(). */ u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe, struct timeval *vblanktime) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; int count = DRM_TIMESTAMP_MAXRETRIES; u32 cur_vblank; if (WARN_ON(pipe >= dev->num_crtcs)) return 0; /* * Vblank timestamps are read lockless. To ensure consistency the vblank * counter is rechecked and ordering is ensured using memory barriers. * This works like a seqlock. The write-side barriers are in store_vblank. */ do { cur_vblank = vblank->count; smp_rmb(); *vblanktime = vblanktimestamp(dev, pipe, cur_vblank); smp_rmb(); } while (cur_vblank != vblank->count && --count > 0); return cur_vblank; } EXPORT_SYMBOL(drm_vblank_count_and_time); /** * 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 struct timeval to receive the vblank timestamp. * * Fetches the "cooked" vblank count value that represents the number of * vblank events since the system was booted, including lost events due to * modesetting activity. Returns corresponding system timestamp of the time * of the vblank interval that corresponds to the current vblank counter value. * * This is the native KMS version of drm_vblank_count_and_time(). */ u32 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc, struct timeval *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, unsigned long seq, struct timeval *now) { assert_spin_locked(&dev->event_lock); e->event.sequence = seq; e->event.tv_sec = now->tv_sec; e->event.tv_usec = now->tv_usec; list_add_tail(&e->base.link, &e->base.file_priv->event_list); wake_up_interruptible(&e->base.file_priv->event_wait); } /** * drm_arm_vblank_event - arm vblank event after pageflip * @dev: DRM device * @pipe: CRTC index * @e: the event to prepare 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. * * Caller must hold event lock. Caller must also hold a vblank reference for * the event @e, which will be dropped when the next vblank arrives. * * This is the legacy version of drm_crtc_arm_vblank_event(). */ void drm_arm_vblank_event(struct drm_device *dev, unsigned int pipe, struct drm_pending_vblank_event *e) { assert_spin_locked(&dev->event_lock); e->pipe = pipe; e->event.sequence = drm_vblank_count(dev, pipe); list_add_tail(&e->base.link, &dev->vblank_event_list); } EXPORT_SYMBOL(drm_arm_vblank_event); /** * 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. * * Caller must hold event lock. Caller must also hold a vblank reference for * the event @e, which will be dropped when the next vblank arrives. * * This is the native KMS version of drm_arm_vblank_event(). */ void drm_crtc_arm_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e) { drm_arm_vblank_event(crtc->dev, drm_crtc_index(crtc), e); } EXPORT_SYMBOL(drm_crtc_arm_vblank_event); /** * drm_send_vblank_event - helper to send vblank event after pageflip * @dev: DRM device * @pipe: CRTC index * @e: the event to send * * Updates sequence # and timestamp on event, and sends it to userspace. * Caller must hold event lock. * * This is the legacy version of drm_crtc_send_vblank_event(). */ void drm_send_vblank_event(struct drm_device *dev, unsigned int pipe, struct drm_pending_vblank_event *e) { struct timeval now; unsigned int seq; if (dev->num_crtcs > 0) { seq = drm_vblank_count_and_time(dev, pipe, &now); } else { seq = 0; now = get_drm_timestamp(); } e->pipe = pipe; send_vblank_event(dev, e, seq, &now); } EXPORT_SYMBOL(drm_send_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, and sends it to userspace. * Caller must hold event lock. * * This is the native KMS version of drm_send_vblank_event(). */ void drm_crtc_send_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e) { drm_send_vblank_event(crtc->dev, drm_crtc_index(crtc), e); } EXPORT_SYMBOL(drm_crtc_send_vblank_event); /** * drm_vblank_enable - enable the vblank interrupt on a CRTC * @dev: DRM device * @pipe: CRTC index * * Returns: * Zero on success or a negative error code on failure. */ 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 = dev->driver->enable_vblank(dev, pipe); DRM_DEBUG("enabling vblank on crtc %u, ret: %d\n", pipe, ret); if (ret) atomic_dec(&vblank->refcount); else { vblank->enabled = true; drm_update_vblank_count(dev, pipe, 0); } } spin_unlock(&dev->vblank_time_lock); return ret; } /** * drm_vblank_get - get a reference count on vblank events * @dev: DRM device * @pipe: index of CRTC to own * * Acquire a reference count on vblank events to avoid having them disabled * while in use. * * This is the legacy version of drm_crtc_vblank_get(). * * Returns: * Zero on success or a negative error code on failure. */ 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 (!dev->num_crtcs) return -EINVAL; if (WARN_ON(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; } EXPORT_SYMBOL(drm_vblank_get); /** * 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. * * This is the native kms version of drm_vblank_get(). * * 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); /** * drm_vblank_put - release ownership of vblank events * @dev: DRM device * @pipe: index of CRTC to release * * Release ownership of a given vblank counter, turning off interrupts * if possible. Disable interrupts after drm_vblank_offdelay milliseconds. * * This is the legacy version of drm_crtc_vblank_put(). */ void drm_vblank_put(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; if (WARN_ON(pipe >= dev->num_crtcs)) return; if (WARN_ON(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 vblank_disable_fn((unsigned long)vblank); } } EXPORT_SYMBOL(drm_vblank_put); /** * 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. * * This is the native kms version of drm_vblank_put(). */ 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. */ void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; int ret; u32 last; if (WARN_ON(pipe >= dev->num_crtcs)) return; ret = drm_vblank_get(dev, pipe); if (WARN(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)); WARN(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_vblank_off - disable vblank events on a CRTC * @dev: DRM device * @pipe: CRTC index * * 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. * * This is the legacy version of drm_crtc_vblank_off(). */ void drm_vblank_off(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; struct drm_pending_vblank_event *e, *t; struct timeval now; unsigned long irqflags; unsigned int seq; if (WARN_ON(pipe >= dev->num_crtcs)) return; spin_lock_irqsave(&dev->event_lock, irqflags); spin_lock(&dev->vbl_lock); DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n", pipe, vblank->enabled, vblank->inmodeset); /* Avoid redundant vblank disables without previous drm_vblank_on(). */ if (drm_core_check_feature(dev, DRIVER_ATOMIC) || !vblank->inmodeset) 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_DEBUG("Sending premature vblank event on disable: " "wanted %d, current %d\n", e->event.sequence, seq); list_del(&e->base.link); drm_vblank_put(dev, pipe); send_vblank_event(dev, e, seq, &now); } spin_unlock_irqrestore(&dev->event_lock, irqflags); } EXPORT_SYMBOL(drm_vblank_off); /** * 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. * * This is the native kms version of drm_vblank_off(). */ void drm_crtc_vblank_off(struct drm_crtc *crtc) { drm_vblank_off(crtc->dev, drm_crtc_index(crtc)); } 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. */ void drm_crtc_vblank_reset(struct drm_crtc *crtc) { struct drm_device *dev = crtc->dev; unsigned long irqflags; unsigned int pipe = drm_crtc_index(crtc); struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; spin_lock_irqsave(&dev->vbl_lock, irqflags); /* * 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_irqrestore(&dev->vbl_lock, irqflags); WARN_ON(!list_empty(&dev->vblank_event_list)); } EXPORT_SYMBOL(drm_crtc_vblank_reset); /** * drm_vblank_on - enable vblank events on a CRTC * @dev: DRM device * @pipe: CRTC index * * This functions restores the vblank interrupt state captured with * drm_vblank_off() again. Note that calls to drm_vblank_on() and * drm_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. * * This is the legacy version of drm_crtc_vblank_on(). */ void drm_vblank_on(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; unsigned long irqflags; if (WARN_ON(pipe >= dev->num_crtcs)) return; spin_lock_irqsave(&dev->vbl_lock, irqflags); DRM_DEBUG_VBL("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) WARN_ON(drm_vblank_enable(dev, pipe)); spin_unlock_irqrestore(&dev->vbl_lock, irqflags); } EXPORT_SYMBOL(drm_vblank_on); /** * drm_crtc_vblank_on - enable vblank events on a CRTC * @crtc: CRTC in question * * This functions restores the vblank interrupt state captured with * drm_vblank_off() again. Note that calls to drm_vblank_on() and * drm_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. * * This is the native kms version of drm_vblank_on(). */ void drm_crtc_vblank_on(struct drm_crtc *crtc) { drm_vblank_on(crtc->dev, drm_crtc_index(crtc)); } EXPORT_SYMBOL(drm_crtc_vblank_on); /** * drm_vblank_pre_modeset - account for vblanks across mode sets * @dev: DRM device * @pipe: CRTC index * * Account for vblank events across mode setting events, which will likely * reset the hardware frame counter. * * This is done by grabbing a temporary vblank reference to ensure that the * vblank interrupt keeps running across the modeset sequence. With this the * software-side vblank frame counting will ensure that there are no jumps or * discontinuities. * * Unfortunately this approach is racy and also doesn't work when the vblank * interrupt stops running, e.g. across system suspend resume. It is therefore * highly recommended that drivers use the newer drm_vblank_off() and * drm_vblank_on() instead. drm_vblank_pre_modeset() only works correctly when * using "cooked" software vblank frame counters and not relying on any hardware * counters. * * Drivers must call drm_vblank_post_modeset() when re-enabling the same crtc * again. */ void drm_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 (!dev->num_crtcs) return; if (WARN_ON(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; } } EXPORT_SYMBOL(drm_vblank_pre_modeset); /** * drm_vblank_post_modeset - undo drm_vblank_pre_modeset changes * @dev: DRM device * @pipe: CRTC index * * This function again drops the temporary vblank reference acquired in * drm_vblank_pre_modeset. */ void drm_vblank_post_modeset(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; unsigned long irqflags; /* vblank is not initialized (IRQ not installed ?), or has been freed */ if (!dev->num_crtcs) return; if (WARN_ON(pipe >= dev->num_crtcs)) return; if (vblank->inmodeset) { spin_lock_irqsave(&dev->vbl_lock, irqflags); dev->vblank_disable_allowed = true; drm_reset_vblank_timestamp(dev, pipe); spin_unlock_irqrestore(&dev->vbl_lock, irqflags); if (vblank->inmodeset & 0x2) drm_vblank_put(dev, pipe); vblank->inmodeset = 0; } } EXPORT_SYMBOL(drm_vblank_post_modeset); static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe) { struct drm_pending_vblank_event *e, *t; struct timeval now; unsigned int 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 ((seq - e->event.sequence) > (1<<23)) continue; DRM_DEBUG("vblank event on %d, current %d\n", e->event.sequence, seq); list_del(&e->base.link); drm_vblank_put(dev, pipe); // send_vblank_event(dev, e, seq, &now); } } /** * 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; if (WARN_ON_ONCE(!dev->num_crtcs)) return false; if (WARN_ON(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, DRM_CALLED_FROM_VBLIRQ); spin_unlock(&dev->vblank_time_lock); wake_up(&vblank->queue); drm_handle_vblank_events(dev, pipe); spin_unlock_irqrestore(&dev->event_lock, irqflags); 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(). * * 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); /** * drm_vblank_no_hw_counter - "No hw counter" implementation of .get_vblank_counter() * @dev: DRM device * @pipe: CRTC for which to read the counter * * Drivers can plug this into the .get_vblank_counter() function if * there is no useable hardware frame counter available. * * Returns: * 0 */ u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe) { return 0; } EXPORT_SYMBOL(drm_vblank_no_hw_counter);