[PATCH v4 6/7] phy: exynos5-usbdrd: subscribe to orientation notifier if required

[Peter Griffin]

Hi André,

Firstly, thanks for all your work getting USB on Pixel 6 / gs101
working upstream :)

On Fri, 6 Dec 2024 at 16:31, André Draszik <andre.draszik at linaro.org> wrote:
>
> gs101's SS phy needs to be configured differently based on the
> connector orientation, as the SS link can only be established if the
> mux is configured correctly.
>
> The code to handle programming of the mux is in place already, this commit
> now adds the missing pieces to subscribe to the Type-C orientation
> switch event.
>
> Note that for this all to work we rely on the USB controller
> re-initialising us. It should invoke our .exit() upon cable unplug, and
> during cable plug we'll receive the orientation event after which we
> expect our .init() to be called.
>
> Above reinitialisation happens if the DWC3 controller can enter runtime
> suspend automatically. For the DWC3 driver, this is an opt-in:
>     echo auto > /sys/devices/.../11110000.usb/power/control
> Once done, things work as long as the UDC is not bound as otherwise it
> stays busy because it doesn't cancel / stop outstanding TRBs. For now
> we have to manually unbind the UDC in that case:
>      echo "" > sys/kernel/config/usb_gadget/.../UDC
>
> Note that if the orientation-switch property is missing from the DT,
> the code will behave as before this commit (meaning for gs101 it will
> work in SS mode in one orientation only). Other platforms are not
> affected either way.
>
> Signed-off-by: André Draszik <andre.draszik at linaro.org>

Reviewed-by: Peter Griffin <peter.griffin at linaro.org>
Tested-by: Peter Griffin <peter.griffin at linaro.org>

Notes on testing:

I tested this series with the corresponding DT using a Pixel 6 device
with 2 different USB hubs and also plugging directly into my laptop.
I've tried various combinations of plugging / unplugging from both
ends of the USB cable and changing cable orientation. With the latest
series the disconnect/reconnect always seems robustly detected and
Pixel is enumerated as a USB device by the host, adb connection to the
phone is possible even with the cable orientation changing between
disconnect/reconnect.

One thing I did notice during testing is that in one cable orientation
Pixel is detected as a `SuperSpeed USB device` by the host and in the
other cable orientation it is detected as a `high-speed USB device`.
Which suggests there is still a latent bug in the phy
re-configuration. Although I think it is fine to fix this
incrementally, as prior to this series the other cable orientation
didn't work at all.

I just tested my personal Pixel 6 running the downstream production
drivers, and that is detected as a `SuperSpeed USB device` in both
cable orientations.

Thanks,

Peter