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

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Message-ID: <e5eed281-ee9b-6e1c-caea-1372329316be@redhat.com>
Date:   Mon, 11 Mar 2019 12:04:03 +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 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