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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/gpu/drm/drm_vblank_work.c | |
parent | Initial commit. (diff) | |
download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/gpu/drm/drm_vblank_work.c')
-rw-r--r-- | drivers/gpu/drm/drm_vblank_work.c | 265 |
1 files changed, 265 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_vblank_work.c b/drivers/gpu/drm/drm_vblank_work.c new file mode 100644 index 0000000000..bd481fdd6b --- /dev/null +++ b/drivers/gpu/drm/drm_vblank_work.c @@ -0,0 +1,265 @@ +// SPDX-License-Identifier: MIT + +#include <uapi/linux/sched/types.h> + +#include <drm/drm_print.h> +#include <drm/drm_vblank.h> +#include <drm/drm_vblank_work.h> +#include <drm/drm_crtc.h> + +#include "drm_internal.h" + +/** + * DOC: vblank works + * + * Many DRM drivers need to program hardware in a time-sensitive manner, many + * times with a deadline of starting and finishing within a certain region of + * the scanout. Most of the time the safest way to accomplish this is to + * simply do said time-sensitive programming in the driver's IRQ handler, + * which allows drivers to avoid being preempted during these critical + * regions. Or even better, the hardware may even handle applying such + * time-critical programming independently of the CPU. + * + * While there's a decent amount of hardware that's designed so that the CPU + * doesn't need to be concerned with extremely time-sensitive programming, + * there's a few situations where it can't be helped. Some unforgiving + * hardware may require that certain time-sensitive programming be handled + * completely by the CPU, and said programming may even take too long to + * handle in an IRQ handler. Another such situation would be where the driver + * needs to perform a task that needs to complete within a specific scanout + * period, but might possibly block and thus cannot be handled in an IRQ + * context. Both of these situations can't be solved perfectly in Linux since + * we're not a realtime kernel, and thus the scheduler may cause us to miss + * our deadline if it decides to preempt us. But for some drivers, it's good + * enough if we can lower our chance of being preempted to an absolute + * minimum. + * + * This is where &drm_vblank_work comes in. &drm_vblank_work provides a simple + * generic delayed work implementation which delays work execution until a + * particular vblank has passed, and then executes the work at realtime + * priority. This provides the best possible chance at performing + * time-sensitive hardware programming on time, even when the system is under + * heavy load. &drm_vblank_work also supports rescheduling, so that self + * re-arming work items can be easily implemented. + */ + +void drm_handle_vblank_works(struct drm_vblank_crtc *vblank) +{ + struct drm_vblank_work *work, *next; + u64 count = atomic64_read(&vblank->count); + bool wake = false; + + assert_spin_locked(&vblank->dev->event_lock); + + list_for_each_entry_safe(work, next, &vblank->pending_work, node) { + if (!drm_vblank_passed(count, work->count)) + continue; + + list_del_init(&work->node); + drm_vblank_put(vblank->dev, vblank->pipe); + kthread_queue_work(vblank->worker, &work->base); + wake = true; + } + if (wake) + wake_up_all(&vblank->work_wait_queue); +} + +/* Handle cancelling any pending vblank work items and drop respective vblank + * references in response to vblank interrupts being disabled. + */ +void drm_vblank_cancel_pending_works(struct drm_vblank_crtc *vblank) +{ + struct drm_vblank_work *work, *next; + + assert_spin_locked(&vblank->dev->event_lock); + + list_for_each_entry_safe(work, next, &vblank->pending_work, node) { + list_del_init(&work->node); + drm_vblank_put(vblank->dev, vblank->pipe); + } + + wake_up_all(&vblank->work_wait_queue); +} + +/** + * drm_vblank_work_schedule - schedule a vblank work + * @work: vblank work to schedule + * @count: target vblank count + * @nextonmiss: defer until the next vblank if target vblank was missed + * + * Schedule @work for execution once the crtc vblank count reaches @count. + * + * If the crtc vblank count has already reached @count and @nextonmiss is + * %false the work starts to execute immediately. + * + * If the crtc vblank count has already reached @count and @nextonmiss is + * %true the work is deferred until the next vblank (as if @count has been + * specified as crtc vblank count + 1). + * + * If @work is already scheduled, this function will reschedule said work + * using the new @count. This can be used for self-rearming work items. + * + * Returns: + * %1 if @work was successfully (re)scheduled, %0 if it was either already + * scheduled or cancelled, or a negative error code on failure. + */ +int drm_vblank_work_schedule(struct drm_vblank_work *work, + u64 count, bool nextonmiss) +{ + struct drm_vblank_crtc *vblank = work->vblank; + struct drm_device *dev = vblank->dev; + u64 cur_vbl; + unsigned long irqflags; + bool passed, inmodeset, rescheduling = false, wake = false; + int ret = 0; + + spin_lock_irqsave(&dev->event_lock, irqflags); + if (work->cancelling) + goto out; + + spin_lock(&dev->vbl_lock); + inmodeset = vblank->inmodeset; + spin_unlock(&dev->vbl_lock); + if (inmodeset) + goto out; + + if (list_empty(&work->node)) { + ret = drm_vblank_get(dev, vblank->pipe); + if (ret < 0) + goto out; + } else if (work->count == count) { + /* Already scheduled w/ same vbl count */ + goto out; + } else { + rescheduling = true; + } + + work->count = count; + cur_vbl = drm_vblank_count(dev, vblank->pipe); + passed = drm_vblank_passed(cur_vbl, count); + if (passed) + drm_dbg_core(dev, + "crtc %d vblank %llu already passed (current %llu)\n", + vblank->pipe, count, cur_vbl); + + if (!nextonmiss && passed) { + drm_vblank_put(dev, vblank->pipe); + ret = kthread_queue_work(vblank->worker, &work->base); + + if (rescheduling) { + list_del_init(&work->node); + wake = true; + } + } else { + if (!rescheduling) + list_add_tail(&work->node, &vblank->pending_work); + ret = true; + } + +out: + spin_unlock_irqrestore(&dev->event_lock, irqflags); + if (wake) + wake_up_all(&vblank->work_wait_queue); + return ret; +} +EXPORT_SYMBOL(drm_vblank_work_schedule); + +/** + * drm_vblank_work_cancel_sync - cancel a vblank work and wait for it to + * finish executing + * @work: vblank work to cancel + * + * Cancel an already scheduled vblank work and wait for its + * execution to finish. + * + * On return, @work is guaranteed to no longer be scheduled or running, even + * if it's self-arming. + * + * Returns: + * %True if the work was cancelled before it started to execute, %false + * otherwise. + */ +bool drm_vblank_work_cancel_sync(struct drm_vblank_work *work) +{ + struct drm_vblank_crtc *vblank = work->vblank; + struct drm_device *dev = vblank->dev; + bool ret = false; + + spin_lock_irq(&dev->event_lock); + if (!list_empty(&work->node)) { + list_del_init(&work->node); + drm_vblank_put(vblank->dev, vblank->pipe); + ret = true; + } + + work->cancelling++; + spin_unlock_irq(&dev->event_lock); + + wake_up_all(&vblank->work_wait_queue); + + if (kthread_cancel_work_sync(&work->base)) + ret = true; + + spin_lock_irq(&dev->event_lock); + work->cancelling--; + spin_unlock_irq(&dev->event_lock); + + return ret; +} +EXPORT_SYMBOL(drm_vblank_work_cancel_sync); + +/** + * drm_vblank_work_flush - wait for a scheduled vblank work to finish + * executing + * @work: vblank work to flush + * + * Wait until @work has finished executing once. + */ +void drm_vblank_work_flush(struct drm_vblank_work *work) +{ + struct drm_vblank_crtc *vblank = work->vblank; + struct drm_device *dev = vblank->dev; + + spin_lock_irq(&dev->event_lock); + wait_event_lock_irq(vblank->work_wait_queue, list_empty(&work->node), + dev->event_lock); + spin_unlock_irq(&dev->event_lock); + + kthread_flush_work(&work->base); +} +EXPORT_SYMBOL(drm_vblank_work_flush); + +/** + * drm_vblank_work_init - initialize a vblank work item + * @work: vblank work item + * @crtc: CRTC whose vblank will trigger the work execution + * @func: work function to be executed + * + * Initialize a vblank work item for a specific crtc. + */ +void drm_vblank_work_init(struct drm_vblank_work *work, struct drm_crtc *crtc, + void (*func)(struct kthread_work *work)) +{ + kthread_init_work(&work->base, func); + INIT_LIST_HEAD(&work->node); + work->vblank = &crtc->dev->vblank[drm_crtc_index(crtc)]; +} +EXPORT_SYMBOL(drm_vblank_work_init); + +int drm_vblank_worker_init(struct drm_vblank_crtc *vblank) +{ + struct kthread_worker *worker; + + INIT_LIST_HEAD(&vblank->pending_work); + init_waitqueue_head(&vblank->work_wait_queue); + worker = kthread_create_worker(0, "card%d-crtc%d", + vblank->dev->primary->index, + vblank->pipe); + if (IS_ERR(worker)) + return PTR_ERR(worker); + + vblank->worker = worker; + + sched_set_fifo(worker->task); + return 0; +} |