-EPROBE_DEFER and failed DSI panel probe

[Andrzej Hajda]

On 15.11.2017 21:26, Eric Anholt wrote:
> I'm happy to have the DSI panel finally working on VC4 (just waiting on
> https://lists.freedesktop.org/archives/dri-devel/2017-October/156407.html),
> but now I've got another problem to solve.  It would be great if I could
> include the DSI panel in our upstream DT, so that it automatically
> worked when you plugged one in.  However, right now we return
> -EPROBE_DEFER during bind unless the panel has actually shown up.  This
> means that if you don't have the panel actually connected, you get this
> sequence at startup:
>
> [   10.719929] [drm] Initialized
> [   10.829510] vc4_hdmi 3f902000.hdmi: vc4-hdmi-hifi <-> 3f902000.hdmi mapping ok
> [   10.844043] vc4-drm soc:gpu: bound 3f902000.hdmi (ops vc4_hdmi_ops [vc4])
> [   10.848626] vc4-drm soc:gpu: bound 3f806000.vec (ops vc4_vec_ops [vc4])
> [   10.850214] vc4-drm soc:gpu: failed to bind 3f700000.dsi (ops vc4_dsi_ops [vc4]): -517
> [   10.856559] vc4-drm soc:gpu: master bind failed: -517
>
> [...]
>
> [   10.967718] rpi_touchscreen 3-0045: Atmel I2C read failed: -6
>
> Once the panel driver fails to probe, we never get asked to re-bind vc4,
> and drm_of_find_panel_or_bridge looks like it would just give us
> -EPROBE_DEFER again since the panel still wasn't registered.
>
> Does anyone have any suggestions for handling this?

I guess you should call component_add only when all required resources
are present(including panel), I suppose moving it to vc4_dsi_host_attach
should help.
Another (maybe better) solution is to look for panel after
mipi_dsi_host_register, but before component_add, and fail if the panel
is not present.

On the other side I am curious why EPROBE_DEFER from bind does not fail
probing of some component (the last one probed), with proper error
propagation it should cause defer_probing of one of the components or
master, and probe/bind should be retried after panel's probe.


Regards
Andrzej



>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel