Re: [RESEND PATCH v3 1/4] dt-bindings: connector: add power-opmode optional property to usb-connector

[Jun Li <lijun.kernel@gmail.com>]

Amelie DELAUNAY <amelie.delaunay@st.com> 于2020年11月5日周四 下午7:36写道：
>
> On 11/4/20 10:08 PM, Rob Herring wrote:
> > On Fri, Oct 30, 2020 at 04:27:14PM +0100, Amelie DELAUNAY wrote:
> >>
> >>
> >> On 10/30/20 3:29 PM, Rob Herring wrote:
> >>> On Thu, Oct 29, 2020 at 11:49 AM Amelie DELAUNAY <amelie.delaunay@st.com> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On 10/29/20 4:40 PM, Rob Herring wrote:
> >>>>> On Thu, Oct 29, 2020 at 10:58:03AM +0100, Amelie Delaunay wrote:
> >>>>>> Power operation mode may depends on hardware design, so, add the optional
> >>>>>> property power-opmode for usb-c connector to select the power operation
> >>>>>> mode capability.
> >>>>>>
> >>>>>> Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
> >>>>>> ---
> >>>>>>     .../bindings/connector/usb-connector.yaml      | 18 ++++++++++++++++++
> >>>>>>     1 file changed, 18 insertions(+)
> >>>>>>
> >>>>>> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> >>>>>> index 728f82db073d..200d19c60fd5 100644
> >>>>>> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> >>>>>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> >>>>>> @@ -93,6 +93,24 @@ properties:
> >>>>>>           - device
> >>>>>>           - dual
> >>>>>>
> >>>>>> +  power-opmode:
> >>>>>
> >>>>> I've acked this version:
> >>>>>
> >>>>> https://lore.kernel.org/r/20201020093627.256885-2-badhri@google.com
> >>>>>
> >>>>
> >>>> frs is used for Fast Role Swap defined in USB PD spec.
> >>>> I understand it allows to get the same information but I'm wondering why
> >>>> the property name is limited to -frs- in this case. What about a
> >>>> non-power delivery USB-C connector ?
> >>>
> >>> I've got no idea. The folks that know USB-C and PD details need to get
> >>> together and work all this out. To me, it looks like the same thing...
> >>>
> >>
> >> It looks but...
> >>
> >> The purpose of power-opmode property is to configure the USB-C controllers,
> >> especially the non-PD USB-C controllers to determine the power operation
> >> mode that the Type C connector will support and will advertise through CC
> >> pins when it has no power delivery support, whatever the power role: Sink,
> >> Source or Dual
> >> The management of the property is the same that data-role and power-role
> >> properties, and done by USB Type-C Connector Class.
> >>
> >> new-source-frs-typec-current specifies initial current capability of the new
> >> source when vSafe5V is applied during PD3.0 Fast Role Swap. So here, this
> >> property is not applied at usb-c controller configuration level, but during
> >> PD Fast Role Swap, so when the Sink become the Source.
> >> Moreover, the related driver code says FRS can only be supported by DRP
> >> ports. So new-source-frs-typec-current property, in addition to being
> >> specific to PD, is also dedicated to DRP usb-c controller.
> >> The property is managed by Type-C Port Controller Manager for PD.
> >
> > But it's the same set of possible values, right? So we can align the
> > values at least.
> >
>
> USB Power Delivery FRS values are defined in
> include/dt-bindings/usb/pd.h

I think this can be changed if both can be aligned.

>to fit with drivers/usb/typec/tcpm/tcpm.c
> frs_typec_current enum.
>
> USB-C power operation mode values are defined in
> include/linux/usb/typec.h with typec_pwr_opmode enum and matching with
> string values of typec_pwr_opmodes tab.
>
> USB PD requires USB-C.
> USB-C doesn't requires USB PD.
>
> drivers/usb/typec/tcpm/tcpm.c already used typec_pwr_opmode values.
>
> USB PD specification Table 6-14 Fixed Supply PDO says:
> Fast Role Swap required USB Type-C Current (see also [USB Type-C 2.0]):
> Value | Description
>   00b  | Fast Swap not supported (default)
>   01b  | Default USB Power
>   10b  | 1.5A @ 5V
>   11b  | 3.0A @ 5V

This is the value in PDO of sink, the FRS property value(or after translated)
actually is used to compare with above value.

So I think both properties can share the same "value", maybe string
like below

  10 static const char * const typec_pwr_opmodes[] = {
  11         [TYPEC_PWR_MODE_USB]    = "default",
  12         [TYPEC_PWR_MODE_1_5A]   = "1.5A",
  13         [TYPEC_PWR_MODE_3_0A]   = "3.0A",

>
> Note the *see also USB Type-C 2.0*.
>
> USB Type-C specification 4.6.2.1 USB Type-C Current says:
> The USB Type-C connector uses CC pins for configuration including an
> ability for a Source to advertise to its port partner (Sink) the amount
> of current it shall supply:
> • Default is the as-configured for high-power operation current value as
> defined by the USB Specification (500 mA for USB 2.0 ports; 900 mA or
> 1,500 mA for USB 3.2 ports in single-lane or dual-lane operation,
> respectively)
> • 1.5 A
> • 3.0 A
>
> > Can we align the names in some way? power-opmode and frs-source-opmode
> > or ??

how about typec-power-opmode and frs-new-source-opmode

> >
>
> I let USB PD specialists answer.
>
> *frs* property fits with USB PD specification, so with USB PD protocol.
> *power-opmode fits with USB Type-C specification, so with USB-C hardware
> support.
>
> > Are these 2 properties mutually exclusive?

I think yes.

thanks
Li Jun
>> If so, that should be
> > captured.
>
> FRS is specific to products with Power Delivery Support.
>
> power-opmode is dedicated to products with USB-C connector support.
>
> Regards,
> Amelie