Hi,
On Thu, Apr 7, 2022 at 4:36 PM Dmitry Baryshkov dmitry.baryshkov@linaro.org wrote:
The ps8640 driver looks 'working by coincidence'. It calls dp_aux_populate, then immediately after the function returns it checks for the panel. If panel-edp is built as a module, the probe might fail easily. The anx7625 driver has the same kind of issue. The DP AUX bus is populated from the probe() and after some additional work the panel is being checked. This design is fragile and from my quick glance it can break (or be broken) too easy. It reminds me of our drm msm 'probe' loops preventing the device to boot completely if the dsi bridge/panel could not be probed in time.
I did spend some time thinking about this, at least for ps8640. I believe that as long as the panel's probe isn't asynchronous. Basically if the panel isn't ready then ps8640 should return and we'll retry later. I do remember the probe loops that we used to have with msm and I don't _think_ this would trigger it.
That being said, if we need to separate out the AUX bus into a sub-device like we did in sn65dsi86 we certainly could.
-Doug