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

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Date:   Wed, 5 Aug 2020 19:22:39 +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: Thursday, July 30, 2020 4:25 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
> 
> Hey Azhar,
> 
> On Thu, Jul 30, 2020 at 11:06:12PM +0000, Shaikh, Azhar wrote:
> > Hi Prashant,
> > >
> > > Since this was the last switch being configured, please maintain the
> > > same order and add this at the end of the function, after the if-else if
> block.
> > >
> >
> > Please correct if my understanding is not correct here:
> > Set the orientation , set the role, then configure the mux. Shouldn't this be
> the order?
> 
> 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.

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


> 
> Please keep in mind that each of these switches (orientation, data-role,
> mode-switch, or what is referred to here as "mux") can theoretically be
> different switches, controlled independently by distinct drivers and
> hardware.
> 
> We should not change what ordering is already present unless there is a
> requirement to do so. The existing ordering was orientation switch, "mux" or
> role switch, then the data-role switch, so let us stick to that.
> 
> Best regards,
> 
> >
> >
> > > Best regards,
> > >
> > > -Prashant

Regards,
Azhar