linux-kernel - Re: [PATCH v3 2/5] media: hantro: Reduce H264 extra space for motion vectors

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Message-ID: <CAAFQd5CZo5g2gtuvU+OuoRj18ZcCH8XEinGyAjRxqUXRfSQhgg@mail.gmail.com>
Date:   Wed, 8 Jan 2020 21:59:32 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Ezequiel Garcia <ezequiel@...labora.com>
Cc:     Jonas Karlman <jonas@...boo.se>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] media: hantro: Reduce H264 extra space for motion vectors

On Tue, Dec 10, 2019 at 3:11 AM Ezequiel Garcia <ezequiel@...labora.com> wrote:
>
> On Wed, 2019-11-20 at 21:44 +0900, Tomasz Figa wrote:
> > Hi Jonas,
> >
> > On Thu, Nov 7, 2019 at 7:34 AM Jonas Karlman <jonas@...boo.se> wrote:
> > > A decoded 8-bit 4:2:0 frame need memory for up to 448 bytes per
> > > macroblock with additional 32 bytes on multi-core variants.
> > >
> > > Memory layout is as follow:
> > >
> > > +---------------------------+
> > > > Y-plane   256 bytes x MBs |
> > > +---------------------------+
> > > > UV-plane  128 bytes x MBs |
> > > +---------------------------+
> > > > MV buffer  64 bytes x MBs |
> > > +---------------------------+
> > > > MC sync          32 bytes |
> > > +---------------------------+
> > >
> > > Reduce the extra space allocated now that motion vector buffer offset no
> > > longer is based on the extra space.
> > >
> > > Only allocate extra space for 64 bytes x MBs of motion vector buffer
> > > and 32 bytes for multi-core sync.
> > >
> > > Fixes: a9471e25629b ("media: hantro: Add core bits to support H264 decoding")
> > > Signed-off-by: Jonas Karlman <jonas@...boo.se>
> > > Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>
> > > ---
> > > Changes in v3:
> > >   - add memory layout to code comment (Boris)
> > > Changes in v2:
> > >   - updated commit message
> > > ---
> > >  drivers/staging/media/hantro/hantro_v4l2.c | 20 ++++++++++++++++++--
> > >  1 file changed, 18 insertions(+), 2 deletions(-)
> > >
> >
> > Thanks for the patch!
> >
> > What platform did you test it on and how? Was it tested with IOMMU enabled?
>
> Hello Tomasz,
>
> Please note that this series has been picked-up and is merged
> in v5.5-rc1.
>
> IIRC, we tested these patches on RK3399 and RK3288 (that means
> with an IOMMU). I've just ran some more extensive tests on RK3288,
> on media/master; and I plan to test some more on RK3399 later this week.
>
> Do you have any specific concern in mind?

I specifically want to know whether we're 100% sure that those sizes
are correct. The IOMMU still works on page granularity so it's
possible that the allocation could be just big enough by luck.

Best regards,
Tomasz