Hi Amelie,

On Mon, Jul 27, 2020 at 11:23 AM Amelie Delaunay [off-list ref] wrote:

This patch adds support for usb role switch to dwc2, by using overriding
control of the PHY voltage valid and ID input signals.

iddig signal (ID) can be overridden:
- when setting GUSBCFG_FORCEHOSTMODE, iddig input pin is overridden with 1;
- when setting GUSBCFG_FORCEDEVMODE, iddig input pin is overridden with 0.

avalid/bvalid/vbusvalid signals can be overridden respectively with:
- GOTGCTL_AVALOEN + GOTGCTL_AVALOVAL
- GOTGCTL_BVALOEN + GOTGCTL_BVALOVAL
- GOTGCTL_VBVALEN + GOTGCTL_VBVALOVAL

It is possible to determine valid sessions thanks to usb role switch:
- if USB_ROLE_NONE then !avalid && !bvalid && !vbusvalid
- if USB_ROLE_DEVICE then !avalid && bvalid && vbusvalid
- if USB_ROLE_HOST then avalid && !bvalid && vbusvalid

Signed-off-by: Amelie Delaunay <redacted>

please add my:
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

The usb_role_switch part looks correct to me
I don't understand the details of the dwc2 hardware well enough to say
if the rest of this patch is fine or not (which is why I'm giving my
Acked-by instead of Reviewed-by).

Unfortunately I'm still fighting with the Amlogic bits (or my
board...) to make this work on my boards.
That why I can't give my Tested-by yet
At the same time I'm confident that the problem lies within the
Amlogic OTG detection/GPIOs so I don't see a reason to hold your patch
up due to this

Finally, please note that there may be a small conflict due to one
bugfix I sent: [0]
I think it will be trivial to solve (since we're both adding a new error label)


Thank you for your good work again!
Best regards,
Martin


[0] https://patchwork.kernel.org/patch/11687357/