linux-kernel - Re: [PATCH v2 2/2] platform/chrome: cros_ec_typec: Avoid setting usb role during disconnect

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Message-ID: <CACeCKaf6WuW6XbFBQoVEW55w=OHfaVmmDn1xepiYYeRyMzZFrA@mail.gmail.com>
Date:   Wed, 5 Aug 2020 12:37:14 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     "Shaikh, Azhar" <azhar.shaikh@...el.com>
Cc:     "bleung@...omium.org" <bleung@...omium.org>,
        "enric.balletbo@...labora.com" <enric.balletbo@...labora.com>,
        "groeck@...omium.org" <groeck@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        "Patel, Utkarsh H" <utkarsh.h.patel@...el.com>,
        "Bowman, Casey G" <casey.g.bowman@...el.com>,
        "Mani, Rajmohan" <rajmohan.mani@...el.com>
Subject: Re: [PATCH v2 2/2] platform/chrome: cros_ec_typec: Avoid setting usb
 role during disconnect

Hi Azhar,


On Wed, Aug 5, 2020 at 12:22 PM Shaikh, Azhar <azhar.shaikh@...el.com> wrote:
>
> Hi Prashant,
>
> > Is this documented anywhere? Kindly provide the links to that if so. I wasn't
> > aware of any ordering requirements (but I may be missing something).
>
> The configuration of the connector should always happen in the order defined in the
> USB Type-C specification. Check ch. 2.3 (USB Type-C Spec R2.0). So that will basically give you:
>
> 1. orientation
> 2. role(s)
> 3. the rest.

Thanks for the link. Are you referring to Section 2.3 (Configuration
Process) ? I couldn't find anything there which
implied any required ordering (I'm reading Release 2.0, Aug 2019, so I
don't know if something has been added since).
Could you kindly point me to the appropriate subsection?

Additionally, I think any ordering requirements there are already
handled by the TCPM in the Chrome OS EC.

>
> Also I see in USB Type-C Port Manager driver the above mentioned sequence being followed
> https://elixir.bootlin.com/linux/latest/source/drivers/usb/typec/tcpm/tcpm.c#L664

In addition to the above, note that this is a TCPM implementation (on
Chrome OS the TCPM implementation is in the EC), so what is
done there doesn't necessarily apply to cros-ec-typec.

Best regards,

-Prashant

>
>
> > > > -Prashant
>
> Regards,
> Azhar