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

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Message-ID: <MWHPR11MB151843C494EAFDAD0DE6BA81914B0@MWHPR11MB1518.namprd11.prod.outlook.com>
Date:   Wed, 5 Aug 2020 20:28:22 +0000
From:   "Shaikh, Azhar" <azhar.shaikh@...el.com>
To:     Prashant Malani <pmalani@...omium.org>
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 Prashant,


> -----Original Message-----
> From: Prashant Malani <pmalani@...omium.org>
> Sent: Wednesday, August 5, 2020 12:37 PM
> To: Shaikh, Azhar <azhar.shaikh@...el.com>
> Cc: bleung@...omium.org; enric.balletbo@...labora.com;
> groeck@...omium.org; linux-kernel@...r.kernel.org;
> 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?

That is the section I was referring to.

> 
> 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