[RFC 5/4] drm/msm: Add deadline based boost support

[RFC 5/4] drm/msm: Add deadline based boost support

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
This is a quick implementation of what I had in mind for driver side
of deadline boost.  For a couple games with bad gpu devfreq behavior
this boosts "Render quality" from ~35% to ~95%.  (The "Render quality"
metric in chrome://arc-overview-tracing is basically a measure of the
deviation in frame/commit time, so 100% would be a consistent fps
with no variantion.)  Not quite 100%, this is still a bit of a re-
active mechanism.

A similar result can be had by tuning devfreq to boost to max OPP at
a much lower threshold of busyness.  With the obvious downside that
you spend a lot of time running the GPU much faster than needed.

 drivers/gpu/drm/msm/msm_fence.c       | 76 +++++++++++++++++++++++++++
 drivers/gpu/drm/msm/msm_fence.h       | 20 +++++++
 drivers/gpu/drm/msm/msm_gpu.h         |  1 +
 drivers/gpu/drm/msm/msm_gpu_devfreq.c | 20 +++++++
 4 files changed, 117 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
index f2cece542c3f..67c2a96e1c85 100644
--- a/drivers/gpu/drm/msm/msm_fence.c
+++ b/drivers/gpu/drm/msm/msm_fence.c
@@ -8,6 +8,37 @@
 
 #include "msm_drv.h"
 #include "msm_fence.h"
+#include "msm_gpu.h"
+
+static inline bool fence_completed(struct msm_fence_context *fctx, uint32_t fence);
+
+static struct msm_gpu *fctx2gpu(struct msm_fence_context *fctx)
+{
+	struct msm_drm_private *priv = fctx->dev->dev_private;
+	return priv->gpu;
+}
+
+static enum hrtimer_restart deadline_timer(struct hrtimer *t)
+{
+	struct msm_fence_context *fctx = container_of(t,
+			struct msm_fence_context, deadline_timer);
+
+	kthread_queue_work(fctx2gpu(fctx)->worker, &fctx->deadline_work);
+
+	return HRTIMER_NORESTART;
+}
+
+static void deadline_work(struct kthread_work *work)
+{
+	struct msm_fence_context *fctx = container_of(work,
+			struct msm_fence_context, deadline_work);
+
+	/* If deadline fence has already passed, nothing to do: */
+	if (fence_completed(fctx, fctx->next_deadline_fence))
+		return;
+
+	msm_devfreq_boost(fctx2gpu(fctx), 2);
+}
 
 
 struct msm_fence_context *
@@ -26,6 +57,13 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr,
 	fctx->fenceptr = fenceptr;
 	spin_lock_init(&fctx->spinlock);
 
+	hrtimer_init(&fctx->deadline_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	fctx->deadline_timer.function = deadline_timer;
+
+	kthread_init_work(&fctx->deadline_work, deadline_work);
+
+	fctx->next_deadline = ktime_get();
+
 	return fctx;
 }
 
@@ -49,6 +87,8 @@ void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence)
 {
 	spin_lock(&fctx->spinlock);
 	fctx->completed_fence = max(fence, fctx->completed_fence);
+	if (fence_completed(fctx, fctx->next_deadline_fence))
+		hrtimer_cancel(&fctx->deadline_timer);
 	spin_unlock(&fctx->spinlock);
 }
 
@@ -79,10 +119,46 @@ static bool msm_fence_signaled(struct dma_fence *fence)
 	return fence_completed(f->fctx, f->base.seqno);
 }
 
+static void msm_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
+{
+	struct msm_fence *f = to_msm_fence(fence);
+	struct msm_fence_context *fctx = f->fctx;
+	unsigned long flags;
+	ktime_t now;
+
+	spin_lock_irqsave(&fctx->spinlock, flags);
+	now = ktime_get();
+
+	if (ktime_after(now, fctx->next_deadline) ||
+			ktime_before(deadline, fctx->next_deadline)) {
+		fctx->next_deadline = deadline;
+		fctx->next_deadline_fence =
+			max(fctx->next_deadline_fence, (uint32_t)fence->seqno);
+
+		/*
+		 * Set timer to trigger boost 3ms before deadline, or
+		 * if we are already less than 3ms before the deadline
+		 * schedule boost work immediately.
+		 */
+		deadline = ktime_sub(deadline, ms_to_ktime(3));
+
+		if (ktime_after(now, deadline)) {
+			kthread_queue_work(fctx2gpu(fctx)->worker,
+					&fctx->deadline_work);
+		} else {
+			hrtimer_start(&fctx->deadline_timer, deadline,
+					HRTIMER_MODE_ABS);
+		}
+	}
+
+	spin_unlock_irqrestore(&fctx->spinlock, flags);
+}
+
 static const struct dma_fence_ops msm_fence_ops = {
 	.get_driver_name = msm_fence_get_driver_name,
 	.get_timeline_name = msm_fence_get_timeline_name,
 	.signaled = msm_fence_signaled,
+	.set_deadline = msm_fence_set_deadline,
 };
 
 struct dma_fence *
diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h
index 4783db528bcc..d34e853c555a 100644
--- a/drivers/gpu/drm/msm/msm_fence.h
+++ b/drivers/gpu/drm/msm/msm_fence.h
@@ -50,6 +50,26 @@ struct msm_fence_context {
 	volatile uint32_t *fenceptr;
 
 	spinlock_t spinlock;
+
+	/*
+	 * TODO this doesn't really deal with multiple deadlines, like
+	 * if userspace got multiple frames ahead.. OTOH atomic updates
+	 * don't queue, so maybe that is ok
+	 */
+
+	/** next_deadline: Time of next deadline */
+	ktime_t next_deadline;
+
+	/**
+	 * next_deadline_fence:
+	 *
+	 * Fence value for next pending deadline.  The deadline timer is
+	 * canceled when this fence is signaled.
+	 */
+	uint32_t next_deadline_fence;
+
+	struct hrtimer deadline_timer;
+	struct kthread_work deadline_work;
 };
 
 struct msm_fence_context * msm_fence_context_alloc(struct drm_device *dev,
diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index 0e4b45bff2e6..e031c9b495ed 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -425,6 +425,7 @@ void msm_devfreq_init(struct msm_gpu *gpu);
 void msm_devfreq_cleanup(struct msm_gpu *gpu);
 void msm_devfreq_resume(struct msm_gpu *gpu);
 void msm_devfreq_suspend(struct msm_gpu *gpu);
+void msm_devfreq_boost(struct msm_gpu *gpu, unsigned factor);
 void msm_devfreq_active(struct msm_gpu *gpu);
 void msm_devfreq_idle(struct msm_gpu *gpu);
 
diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index 0a1ee20296a2..8a8d7b9028a3 100644
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -144,6 +144,26 @@ void msm_devfreq_suspend(struct msm_gpu *gpu)
 	devfreq_suspend_device(gpu->devfreq.devfreq);
 }
 
+void msm_devfreq_boost(struct msm_gpu *gpu, unsigned factor)
+{
+	struct msm_gpu_devfreq *df = &gpu->devfreq;
+	unsigned long freq;
+
+	/*
+	 * Hold devfreq lock to synchronize with get_dev_status()/
+	 * target() callbacks
+	 */
+	mutex_lock(&df->devfreq->lock);
+
+	freq = get_freq(gpu);
+
+	freq *= factor;
+
+	msm_devfreq_target(&gpu->pdev->dev, &freq, 0);
+
+	mutex_unlock(&df->devfreq->lock);
+}
+
 void msm_devfreq_active(struct msm_gpu *gpu)
 {
 	struct msm_gpu_devfreq *df = &gpu->devfreq;
-- 
2.31.1