Message-ID: <9376817c-30f1-4ca1-afde-60ebdfd93f53@google.com>
Date: Wed, 28 May 2025 11:42:24 -0700
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: Rob Herring <robh@...nel.org>
Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Badhri Jagan Sridharan <badhri@...gle.com>,
 Sebastian Reichel <sre@...nel.org>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <len.brown@...el.com>,
 Pavel Machek <pavel@...nel.org>, Kyle Tso <kyletso@...gle.com>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
 tudor.ambarus@...aro.org, andre.draszik@...aro.org, peter.griffin@...aro.org
Subject: Re: [PATCH v2 1/5] dt-bindings: connector: extend ports property to
 model power connections

Hi,

On 5/20/25 1:10 PM, Amit Sunil Dhamne wrote:
> Hi Rob,
>
> Thanks for your response!
>
> On 5/14/25 12:42 PM, Rob Herring wrote:
>> On Wed, May 07, 2025 at 06:00:22PM -0700, Amit Sunil Dhamne wrote:
>>> Extend ports property to model power lines going between connector to
>>> charger or battery/batteries. As an example, connector VBUS can supply
>>> power in & out of the battery for a DRP.
>>>
>>> Additionally, add ports property to maxim,max33359 controller example.
>>>
>>> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
>>> ---
>>>  .../bindings/connector/usb-connector.yaml          | 20 +++++++++++------
>>>  .../devicetree/bindings/usb/maxim,max33359.yaml    | 25 ++++++++++++++++++++++
>>>  2 files changed, 38 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
>>> index 11e40d225b9f3a0d0aeea7bf764f1c00a719d615..706094f890026d324e6ece8b0c1e831d04d51eb7 100644
>>> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
>>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
>>> @@ -181,16 +181,16 @@ properties:
>>>  
>>>    port:
>>>      $ref: /schemas/graph.yaml#/properties/port
>>> -    description: OF graph bindings modeling a data bus to the connector, e.g.
>>> -      there is a single High Speed (HS) port present in this connector. If there
>>> -      is more than one bus (several port, with 'reg' property), they can be grouped
>>> -      under 'ports'.
>>> +    description: OF graph binding to model a logical connection between a device
>>> +      and connector. This connection may represent a data bus or power line. For
>>> +      e.g. a High Speed (HS) data port present in this connector or VBUS line.
>>> +      If there is more than one connection (several port, with 'reg' property),
>>> +      they can be grouped under 'ports'.
>> 'port' and 'port@0' are equivalent. So you can't be changing its 
>> definition.
> Noted!
>
>
>> I'm not sure showing a power connection with the graph is the right 
>> approach.
> I want to provide some more context and rationale behind using this design.
>
> From a hardware perspective:
>
> The max77759/max33359 IC has Type-C port controller, charger, fuel gauge
> (FG) ICs. The Vbus from the connector goes to/from the TCPC and connects
> with the charger IP via circuitry & from there on to the battery. The FG
> is connected to the battery in parallel. As it can be seen that while
> these IPs are interconnected, there's no direct connection of the fuel
> gauge & the connector.
>
> For this feature, I am interested in getting the reference to the FG. As
> per graph description: "...These common bindings do not contain any
> information about the direction or type of the connections, they just
> map their existence." This works for my case because I just want the
> connector to be aware of the Fuel gauge device without imposing a
> specific directionality in terms of power supplier/supplied. This is
> also the reason why I didn't use
> "/schemas/power/supply/power-supply.yaml#power-supplies" binding.
>
>> We have a binding for that already with the regulator binding.
> I haven't explored the option of using regulator bindings. But in my
> case I am interested in fuel gauge and unfortunately, they're modeled as
> power_supply devices.
>
>
>>  
>> Perhaps the connector needs to be a supply. It's already using that 
>> binding in the supplying power to the connector case.
> Want to clarify, in this case you mean
> /schemas/regulator/regulator.yaml#*-supply$ right?
>
> Adding to my response above, the reason I don't want to impose a
> directionality in terms of supplier/supplied is that in case of USB Dual
> Role Port they're dynamic i.e., when USB is source, the power is
> supplied out of the battery (battery/FG will be supplier) and in case
> USB is sink, battery is supplied power. Whether the connector port is in
> source or sink role is determined on a connection to connection basis.
> Also, the knowledge of the supply direction is of no consequence for
> this feature.
>
>
> Please let me know what you think.
>
> Thanks,
>
> Amit


I wanted to follow up on my previous responses. Please let me know if
you have any further questions or concerns.

Thanks,

Amit


>
>> Rob

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