Re: [PATCH v3 5/9] drm/msm: Add deadline based boost support

[Rob Clark]

On Wed, Sep 8, 2021 at 10:48 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Fri, Sep 03, 2021 at 11:47:56AM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> Why do you need a kthread_work here? Is this just to make sure you're
> running at realtime prio? Maybe a comment to that effect would be good.

Mostly because we are already using a kthread_worker for things the
GPU needs to kick off to a different context.. but I think this is
something we'd want at a realtime prio

BR,
-R

> -Daniel
>
> > ---
> >  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
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch