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

[Amelie DELAUNAY <amelie.delaunay@st.com>]

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 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

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 ??
> 

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? 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