linux-kernel - Re: [PATCH v4 2/3] usb: dwc2: override PHY input signals with usb role switch support

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Date:   Mon, 27 Jul 2020 19:55:44 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Amelie Delaunay <amelie.delaunay@...com>
Cc:     Minas Harutyunyan <hminas@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        Fabrice Gasnier <fabrice.gasnier@...com>
Subject: Re: [PATCH v4 2/3] usb: dwc2: override PHY input signals with usb
 role switch support

Hi Amelie,

On Mon, Jul 27, 2020 at 11:23 AM Amelie Delaunay <amelie.delaunay@...com> 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 <amelie.delaunay@...com>
please add my:
Acked-by: Martin Blumenstingl <martin.blumenstingl@...glemail.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/