linux-kernel - Re: [PATCH] media: vb2: always set buffer cache sync hints

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Date:   Sat, 28 Nov 2020 14:04:42 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Tomasz Figa <tfiga@...omium.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH] media: vb2: always set buffer cache sync hints

On (20/11/28 01:50), Tomasz Figa wrote:
> On Sat, Nov 28, 2020 at 1:35 AM Sergey Senozhatsky
> <sergey.senozhatsky@...il.com> wrote:
> >
> > On (20/11/27 15:56), Hans Verkuil wrote:
> > > Yes.
> > >
> > > BTW, wouldn't it be sufficient to change this code to:
> > >
> > >       if (!q->allow_cache_hints && q->memory != VB2_MEMORY_DMABUF) {
> > >               vb->need_cache_sync_on_prepare = 1;
> > >               vb->need_cache_sync_on_finish = 1;
> > >       }
> >
> > I think it would be sufficient.
> 
> Does it matter at this point if allow_cache_hints is set or not?

That's a good question. I'd say that it'll probably make sense to set
need_cache_sync for as many buffers as possible, regardless the queue
configuration (except for ->memory type), just to stay on the safe side.
I can spin another patch version.

	-ss