Re: [PATCH] usb: typec: don't disable sink or source on initialization

[Guenter Roeck]

On 09/09/2018 07:36 AM, Angus Ainslie wrote:
> On 2018-09-09 08:20, Guenter Roeck wrote:
> > On 09/09/2018 07:08 AM, Angus Ainslie wrote:
> > > Hi Guenter
> > >
> > > On 2018-09-07 06:55, Guenter Roeck wrote:
> > > > On 09/07/2018 03:34 AM, Heikki Krogerus wrote:
> > > > > +Guenter
> > > > >
> > > > > On Thu, Sep 06, 2018 at 01:26:44PM -0600, Angus Ainslie (Purism) wrote:
> > > > > > If the board is being powered by USB disabling the source and sink
> > > > > > can remove power from the board. Default to source and sink enabled.
> > > >
> > > > Seems to me that might violate the specification, and cause trouble for systems
> > > > where vbus has to be off initially. It may be better to provide this kind of
> > > > information as configuration parameter instead of imposing it on everyone.
> > >
> > > It felt like it would not be the correct thing to do either. I've tried re-arranging the code in tcpci.c to enable the sink before disabling the source but the only way I found to not disable the power was by setting both of those to true.
> > >
> > > What about adding some device tree entries for the initial vbus state and default to false if they are not present ?
> > >
> > > init-vbus-source and init-vbus-charge ?
> >
> > Yes, I think we should do something along that line. Another question is
> > if we could or should optionally pull the current state from the low level
> > driver, but that may be secondary.
>
> I thought of trying to do that but from reading the "PTN5110N PD PHY application programming guide" there didn't seem to be a direct way to read those parameters.

Let's put that on the backburner (maybe it works for some other chips)
and go with the devicetree property for now.

Guenter


> > Thanks,
> > Guenter
> >
> > > Angus
> > >
> > > > Guenter
> > > >
> > > > > > Signed-off-by: Angus Ainslie (Purism) <angus@xxxxxxxx>
> > > > > > ---
> > > > > > Â drivers/usb/typec/tcpm.c | 8 +++++---
> > > > > > Â 1 file changed, 5 insertions(+), 3 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
> > > > > > index ca7bedb46f7f..a1b819cf31da 100644
> > > > > > --- a/drivers/usb/typec/tcpm.c
> > > > > > +++ b/drivers/usb/typec/tcpm.c
> > > > > > @@ -2462,9 +2462,11 @@ static int tcpm_init_vbus(struct tcpm_port *port)
> > > > > > Â {
> > > > > > ÂÂÂÂÂ int ret;
> > > > > > Â -ÂÂÂ ret = port->tcpc->set_vbus(port->tcpc, false, false);
> > > > > > -ÂÂÂ port->vbus_source = false;
> > > > > > -ÂÂÂ port->vbus_charge = false;
> > > > > > +ÂÂÂ /* default to source and sink enabled in case USB is our only power
> > > > > > +ÂÂÂÂ * source */
> > > >
> > > > I am personally in favor of standard multi-line comments.
> > > >
> > > > > > +ÂÂÂ ret = port->tcpc->set_vbus(port->tcpc, true, true);
> > > > > > +ÂÂÂ port->vbus_source = true;
> > > > > > +ÂÂÂ port->vbus_charge = true;
> > > > > > ÂÂÂÂÂ return ret;
> > > > > > Â }