On Fri, Sep 03, 2021 at 11:47:52AM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> Add a way to hint to the fence signaler of an upcoming deadline, such as
> vblank, which the fence waiter would prefer not to miss. This is to aid
> the fence signaler in making power management decisions, like boosting
> frequency as the deadline approaches and awareness of missing deadlines
> so that can be factored in to the frequency scaling.
>
> v2: Drop dma_fence::deadline and related logic to filter duplicate
> deadlines, to avoid increasing dma_fence size. The fence-context
> implementation will need similar logic to track deadlines of all
> the fences on the same timeline. [ckoenig]
>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
> drivers/dma-buf/dma-fence.c | 20 ++++++++++++++++++++
> include/linux/dma-fence.h | 16 ++++++++++++++++
> 2 files changed, 36 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index ce0f5eff575d..1f444863b94d 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -910,6 +910,26 @@ dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
> }
> EXPORT_SYMBOL(dma_fence_wait_any_timeout);
>
> +
> +/**
> + * dma_fence_set_deadline - set desired fence-wait deadline
> + * @fence: the fence that is to be waited on
> + * @deadline: the time by which the waiter hopes for the fence to be
> + * signaled
> + *
> + * Inform the fence signaler of an upcoming deadline, such as vblank, by
> + * which point the waiter would prefer the fence to be signaled by. This
> + * is intended to give feedback to the fence signaler to aid in power
> + * management decisions, such as boosting GPU frequency if a periodic
> + * vblank deadline is approaching.
> + */
> +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> +{
> + if (fence->ops->set_deadline && !dma_fence_is_signaled(fence))
> + fence->ops->set_deadline(fence, deadline);
> +}
> +EXPORT_SYMBOL(dma_fence_set_deadline);
> +
> /**
> * dma_fence_init - Initialize a custom fence.
> * @fence: the fence to initialize
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 6ffb4b2c6371..9c809f0d5d0a 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -99,6 +99,7 @@ enum dma_fence_flag_bits {
> DMA_FENCE_FLAG_SIGNALED_BIT,
> DMA_FENCE_FLAG_TIMESTAMP_BIT,
> DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
> + DMA_FENCE_FLAG_HAS_DEADLINE_BIT,
> DMA_FENCE_FLAG_USER_BITS, /* must always be last member */
> };
>
> @@ -261,6 +262,19 @@ struct dma_fence_ops {
> */
> void (*timeline_value_str)(struct dma_fence *fence,
> char *str, int size);
> +
> + /**
> + * @set_deadline:
> + *
> + * Callback to allow a fence waiter to inform the fence signaler of an
> + * upcoming deadline, such as vblank, by which point the waiter would
> + * prefer the fence to be signaled by. This is intended to give feedback
> + * to the fence signaler to aid in power management decisions, such as
> + * boosting GPU frequency.
Please add here that this callback is called without &dma_fence.lock held,
and that locking is up to callers if they have some state to manage.
I realized that while scratching some heads over your later patches.
-Daniel
> + *
> + * This callback is optional.
> + */
> + void (*set_deadline)(struct dma_fence *fence, ktime_t deadline);
> };
>
> void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
> @@ -586,6 +600,8 @@ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
> return ret < 0 ? ret : 0;
> }
>
> +void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline);
> +
> struct dma_fence *dma_fence_get_stub(void);
> struct dma_fence *dma_fence_allocate_private_stub(void);
> u64 dma_fence_context_alloc(unsigned num);
> --
> 2.31.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
