[Linaro-mm-sig] [PATCH] dma-buf/dma_resv_usage: update explicit sync documentation

[Daniel Vetter]

On Wed, Jul 13, 2022 at 01:27:13PM +0200, Bas Nieuwenhuizen wrote:
> With that changed
> 
> Reviewed-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>

Yeah this is a nice clarification.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

In case it hasn't landed yet or so.
-Daniel

> 
> Thanks!
> 
> On Tue, Jul 12, 2022 at 3:23 PM Christian König
> <christian.koenig at amd.com> wrote:
> >
> > Am 12.07.22 um 15:20 schrieb Alex Deucher:
> > > On Tue, Jul 12, 2022 at 9:12 AM Christian König
> > > <ckoenig.leichtzumerken at gmail.com> wrote:
> > >> Make it clear that DMA_RESV_USAGE_BOOKMARK can be used for explicit synced
> > > DMA_RESV_USAGE_BOOKKEEP?
> >
> > Crappy autocorrect and copy&paste. Thanks for pointing that out.
> >
> > Christian.
> >
> > >
> > >> user space submissions as well and document the rules around adding the
> > >> same fence with different usages.
> > >>
> > >> Signed-off-by: Christian König <christian.koenig at amd.com>
> > >> ---
> > >>   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 at amd.com>
> > >
> > > 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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> > >> To unsubscribe send an email to linaro-mm-sig-leave at lists.linaro.org
> >

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