linux-kernel - Re: [PATCH 3/3] drm: omapdrm: Do no allocate non-scanout GEMs through DMM/TILER

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Message-ID: <CAMSo37XdZSZUHLWJj373DdtOBA9=uD8SJ7ywWCYF2pU1i4cB_g@mail.gmail.com>
Date:   Fri, 12 Aug 2022 12:35:12 +0800
From:   Yongqin Liu <yongqin.liu@...aro.org>
To:     Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
Cc:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, tomba@...nel.org,
        airlied@...ux.ie, daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        merlijn@...zup.org, tony@...mide.com,
        "Bajjuri, Praneeth" <praneeth@...com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH 3/3] drm: omapdrm: Do no allocate non-scanout GEMs through DMM/TILER

Hi, Ivaylo, Tomi

We have one X15 Android AOSP master build, it could not have the home
screen displayed
on the hdmi monitor connected with this change, with the following
message printed on the serial console
    [  607.404205] omapdrm omapdrm.0: Failed to setup plane plane-0
    [  607.410522] omapdrm omapdrm.0: Failed to setup plane plane-1
    [  607.416381] omapdrm omapdrm.0: Failed to setup plane plane-2
    [  607.422088] omapdrm omapdrm.0: Failed to setup plane plane-3

   # for details, please check the link here: http://ix.io/47m1

It will work with home screen displayed on the hdmi monitor if this
change is reverted.

Is this the broken problem you talked about here?

And could you please give some suggestions on how to have the x15
Android build work with this change?

Thanks,
Yongqin Liu
On Thu, 17 Feb 2022 at 23:29, Ivaylo Dimitrov
<ivo.g.dimitrov.75@...il.com> wrote:
>
>
>
> On 17.02.22 г. 14:46 ч., Tomi Valkeinen wrote:
> > Hi,
> >
> > On 19/01/2022 12:23, Ivaylo Dimitrov wrote:
> >> On devices with DMM, all allocations are done through either DMM or
> >> TILER.
> >> DMM/TILER being a limited resource means that such allocations will start
> >> to fail before actual free memory is exhausted. What is even worse is
> >> that
> >> with time DMM/TILER space gets fragmented to the point that even if we
> >> have
> >> enough free DMM/TILER space and free memory, allocation fails because
> >> there
> >> is no big enough free block in DMM/TILER space.
> >>
> >> Such failures can be easily observed with OMAP xorg DDX, for example -
> >> starting few GUI applications (so buffers for their windows are
> >> allocated)
> >> and then rotating landscape<->portrait while closing and opening new
> >> windows soon results in allocation failures.
> >>
> >> Fix that by mapping buffers through DMM/TILER only when really needed,
> >> like, for scanout buffers.
> >
> > Doesn't this break users that get a buffer from omapdrm and expect it to
> > be contiguous?
> >
>
> If you mean dumb buffer, then no, this does not break users as dumb
> buffers are allocated as scanout:
>
> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/omapdrm/omap_gem.c#L603
>
> If you mean omap_bo allocated buffers, then if users want
> linear(scanout) buffer, then they request it explicitly by passing
> OMAP_BO_SCANOUT.
>
> Ivo

-- 
Best Regards,
Yongqin Liu
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