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

[John Stultz <john.stultz@linaro.org>]

On Wed, Mar 25, 2020 at 1:17 AM Kalyan Thota <kalyan_t@codeaurora.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@codeaurora.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