On Tue, Jul 12, 2022 at 9:12 AM Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:
>
> Make it clear that DMA_RESV_USAGE_BOOKMARK can be used for explicit synced
DMA_RESV_USAGE_BOOKKEEP?
> user space submissions as well and document the rules around adding the
> same fence with different usages.
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> include/linux/dma-resv.h | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> index c8ccbc94d5d2..264e27e56dff 100644
> --- a/include/linux/dma-resv.h
> +++ b/include/linux/dma-resv.h
> @@ -62,6 +62,11 @@ struct dma_resv_list;
> * For example when asking for WRITE fences then the KERNEL fences are returned
> * as well. Similar when asked for READ fences then both WRITE and KERNEL
> * fences are returned as well.
> + *
> + * Already used fences can be promoted in the sense that a fence with
> + * DMA_RESV_USAGE_BOOKMARK could become DMA_RESV_USAGE_READ by adding it again
Same here.
With that fixed,
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
Alex
> + * with this usage. But fences can never be degraded in the sense that a fence
> + * with DMA_RESV_USAGE_WRITE could become DMA_RESV_USAGE_READ.
> */
> enum dma_resv_usage {
> /**
> @@ -98,10 +103,15 @@ enum dma_resv_usage {
> * @DMA_RESV_USAGE_BOOKKEEP: No implicit sync.
> *
> * This should be used by submissions which don't want to participate in
> - * implicit synchronization.
> + * any implicit synchronization.
> + *
> + * The most common case are preemption fences, page table updates, TLB
> + * flushes as well as explicit synced user submissions.
> *
> - * The most common case are preemption fences as well as page table
> - * updates and their TLB flushes.
> + * Explicit synced user user submissions can be promoted to
> + * DMA_RESV_USAGE_READ or DMA_RESV_USAGE_WRITE as needed using
> + * dma_buf_import_sync_file() when implicit synchronization should
> + * become necessary after initial adding of the fence.
> */
> DMA_RESV_USAGE_BOOKKEEP
> };
> --
> 2.25.1
>
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