linux-kernel - Re: [PATCH 1/5] dt-bindings: connector: add optional properties for Type-B

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Date:   Tue, 12 Mar 2019 10:18:33 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Hans de Goede <hdegoede@...hat.com>, Jun Li <jun.li@....com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Li Jun <jun.li@....com>,
        "Badhri Jagan Sridharan" <badhri@...gle.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Min Guo <min.guo@...iatek.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH 1/5] dt-bindings: connector: add optional properties for
 Type-B

Hi Jun,

   Please pay attention to Hans' comments for your patch

On Mon, 2019-03-11 at 12:04 +0100, Hans de Goede wrote:
> Hi,
> 
> On 11-03-19 12:00, Hans de Goede wrote:
> > Hi,
> > 
> > On 11-03-19 09:06, Hans de Goede wrote:
> >> Hi,
> >>
> >> On 11-03-19 06:33, Chunfeng Yun wrote:
> >>> Hi,
> >>>
> >>> On Fri, 2019-03-08 at 13:07 +0100, Hans de Goede wrote:
> >>>> Hi,
> >>>>
> >>>> On 08-03-19 07:13, Chunfeng Yun wrote:
> >>>>> Add id-gpios, vbus-gpios, vbus-supply and pinctrl properties for
> >>>>> usb-b-connector
> >>>>>
> >>>>> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> >>>>> ---
> >>>>>    .../devicetree/bindings/connector/usb-connector.txt    | 10 ++++++++++
> >>>>>    1 file changed, 10 insertions(+)
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.txt b/Documentation/devicetree/bindings/connector/usb-connector.txt
> >>>>> index a9a2f2fc44f2..7a07b0f4f973 100644
> >>>>> --- a/Documentation/devicetree/bindings/connector/usb-connector.txt
> >>>>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.txt
> >>>>> @@ -17,6 +17,16 @@ Optional properties:
> >>>>>    - self-powered: Set this property if the usb device that has its own power
> >>>>>      source.
> >>>>> +Optional properties for usb-b-connector:
> >>>>> +- id-gpios: gpio for USB ID pin.
> >>>>
> >>>> What about boards where the ID pin is *not* connected to a GPIO,
> >>>> but e.g. to a special pin on the PMIC which can also detect
> >>>> an ACA adapter ? Currently this case is handled by extcon
> >>>> drivers, but we have no way to set e.g. vbus-supply for the
> >>>> connector. Maybe in this case the usb-connector node should
> >>>> be a child of the PMIC node ?
> >>> Yes, it would be, PMIC is in charger of detecting the status of ID pin
> >>
> >> Ok, then I think this should be documented too.
> >>
> >>>> And in many cases there also is a mux to switch the datalines
> >>>> between the host and device(gadget) controllers, how should
> >>>> that be described in this model?  See the new usb-role-switch
> >>>> code under drivers/usb/roles
> >>>>
> >>>> In some cases the mux is controlled through a gpio, so we
> >>>> may want to add a "mux-gpios" here in which case we also
> >>>> need to define what 0/1 means.
> >>> I'm not sure, the mux seems not belong to this connector,
> >>> and may need another driver to register usb-role-switch,
> >>> similar to:
> >>>
> >>> [v2,2/2] usb: typec: add typec switch via GPIO control
> >>> https://patchwork.kernel.org/patch/10834327/
> >>
> >> Right the mux/role-switch will need a driver, but the "owner"
> >> of the usb_connector, e.g. the PMIC or the owner of the
> >> id GPIO pin needs to know which device is the role-switch so
> >> that it can set the role correctly based on the id-pin.
> >>
> >> Your binding already contains Vbus info, allowing the owner
> >> of the usb_connector to enable/disable Vbus based on the id-pin,
> >> but the owner will also be responsible for setting the role-switch.
> >>
> >> Note we cannot simply assume there will be only one role-switch,
> >> we really need some link from the usb_connector to the role-switch
> >> (or if it is a GPIO driven role-switch simply a role-switch-gpios
> >> member in the usb_connector).
> > 
> > I see now in your "[PATCH v3 1/2] dt-bindings: usb: add documentation for
> > typec switch via GPIO" that you plan to use a
> > Documentation/devicetree/bindings/graph.txt style binding for this,
> > adding a remote-endpoint to the orientation-switch (in that patch), or
> > to the role-switch.
> > 
> > But a Type-C port can have both an orientation-switch and a role-switch
> > (and a mux if it supports e.g. DP-altmode), how is the driver driving
> > the device which has the actual usb_c_connecter child-node to which
> > the remote-endpoints for both the orientation- and the role-switch points
> > supposed to figure out which is which ?
> > 
> > Also it feels the wrong-way around to me to have the orientation-switch
> > point to the usb_c_connector, to me it would make more sense to have
> > the usb_c_connector point to a port on the orientation-switch.
> 
> I just noticed you put an "orientation-switch" bool property in the device
> which has the orientation-switch property, if we do something similar for
> the role-switch then that should solve this.
> 
> Regards,
> 
> Hans