linux-kernel - Re: [BUG REPORT] media: coda: mpeg4 decode corruption on i.MX6qp only

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Date:   Mon, 15 Feb 2021 17:10:43 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Philipp Zabel <pza@...gutronix.de>,
        Nicolas Dufresne <nicolas@...fresne.ca>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Adrian Ratiu <adrian.ratiu@...labora.com>,
        Fabio Estevam <festevam@...il.com>,
        linux-media <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG REPORT] media: coda: mpeg4 decode corruption on i.MX6qp
 only

Am Montag, dem 15.02.2021 um 10:54 -0500 schrieb Sven Van Asbroeck:
> Hi Lucas,
> 
> On Mon, Feb 15, 2021 at 5:15 AM Lucas Stach <l.stach@...gutronix.de> wrote:
> > 
> > The straight forward way to fix this would be to just disable the PRE
> > when the stride is getting too large, which might not work well with
> > all userspace requirements, as it effectively disables the ability to
> > scan GPU tiled surfaces when the stride is getting too large.
> 
> Thank you for your very knowledgeable input, really appreciate it.
> 
> I am wondering why I am the first to notice this particular corner
> case. Is this perhaps because X+armada plugin allocate a huge bitmap
> that fits all displays, and other software frameworks do not? Are
> people on i.MX6 mostly using X or Wayland? If Wayland allocates a
> separate bitmap for each display, this PRE bug will of course never
> show up...

Yep, I really doubt that there are a lot i.MX6QP, multi-display, X.Org
based devices out there.

While it's not anywhere in a protocol or similar fixed API, Wayland
compositors mostly opted to have a separate surface per display. The
weston reference compositor started out this way (as it makes surface
repaint easier) and other followed the lead, so Wayland based stacks
won't hit this case.

Regards,
Lucas