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

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Message-ID: <c8084259-74d3-c85f-1275-854826c935a0@redhat.com>
Date:   Mon, 11 Mar 2019 09:06:36 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.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,

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).

Regards,

Hans