linux-kernel - Re: [PATCH 1/2] drm/msm/dpu: add support for color processing blocks in dpu driver

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Date:   Mon, 8 Jun 2020 15:25:48 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Kalyan Thota <kalyan_t@...eaurora.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno@...ts.freedesktop.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, mkrishn@...eaurora.org,
        travitej@...eaurora.org, Doug Anderson <dianders@...omium.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Sean Paul <seanpaul@...omium.org>, hoegsberg@...omium.org,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH 1/2] drm/msm/dpu: add support for color processing blocks
 in dpu driver

On Wed, Mar 25, 2020 at 1:17 AM Kalyan Thota <kalyan_t@...eaurora.org> wrote:
>
> This change adds support to configure dspp blocks in
> the dpu driver.
>
> Macro description of the changes coming in this patch.
> 1) Add dspp definitions in the hw catalog.
> 2) Add capability to reserve dspp blocks in the display data path.
> 3) Attach the reserved block to the encoder.
>
> Signed-off-by: Kalyan Thota <kalyan_t@...eaurora.org>

Hey all,
  With this patch now merged upstream, I'm seeing a regression on
db845c that I bisected down to it.

When I boot up I see:
[   40.976737] [drm:_dpu_rm_check_lm_and_get_connected_blks] [dpu
error]failed to get dspp on lm 0
[   40.985600] [drm:_dpu_rm_check_lm_and_get_connected_blks] [dpu
error]failed to get dspp on lm 0
[   40.994587] [drm:_dpu_rm_check_lm_and_get_connected_blks] [dpu
error]failed to get dspp on lm 0
[   41.003492] [drm:_dpu_rm_check_lm_and_get_connected_blks] [dpu
error]failed to get dspp on lm 0
[   41.012283] [drm:_dpu_rm_make_reservation] [dpu error]unable to
find appropriate mixers
[   41.020369] [drm:dpu_rm_reserve] [dpu error]failed to reserve hw
resources: -119

Over and over, and the display doesn't start up.

I suspect we're supposed to catch the following check before the failure:

+       if (!reqs->topology.num_dspp)
+               return true;

I suspect the issue is in dpu_encoder_get_topology() we don't fully
initialize the topology structure on the stack before returning it.

Does that sound plausible or is there likely some other cause?

thanks
-john