linux-kernel - Re: [PATCH 1/5] dt-bindings: connector: add fixed-batteries property

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Message-ID: <85c6de6a-f8b4-4e4e-8fa2-da53816abc89@google.com>
Date: Fri, 14 Mar 2025 17:56:37 -0700
From: Amit Sunil Dhamne <amitsd@...gle.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Rob Herring <robh@...nel.org>, 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>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-pm@...r.kernel.org, RD Babiera <rdbabiera@...gle.com>,
 Kyle Tso <kyletso@...gle.com>
Subject: Re: [PATCH 1/5] dt-bindings: connector: add fixed-batteries property

Hi Krzysztof,

On 3/13/25 1:48 AM, Krzysztof Kozlowski wrote:
> On Wed, Mar 12, 2025 at 04:42:01PM -0700, Amit Sunil Dhamne wrote:
>> Add a new "fixed-batteries" DT property to connector class. This
>> property is populated with nodes associated with battery type power
>> supplies powering the USB PD connector. This is needed by the Type-C
>> Port Manager (TCPM) to query psy properties which are used to feed
> What is "psy" in terms of bindings?
In terms of bindings this should be a phandle to a device that 
owns/manages the battery (whose driver will eventually call 
devm_power_supply_register to register the battery). This could be a 
fuel-guage ("sprd,sc2731-fgu", say), charger ("ti,bq24190") or a 
platform device ("cw2015") containing "monitored-battery" property to 
manage the simple battery.
>> Battery_Status & Battery_Capacity AMS.
>>
>> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
>> ---
>>   Documentation/devicetree/bindings/connector/usb-connector.yaml | 8 ++++++++
>>   Documentation/devicetree/bindings/usb/maxim,max33359.yaml      | 1 +
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
>> index 11e40d225b9f3a0d0aeea7bf764f1c00a719d615..5e15bc060f5a2cfce842f83de738f1e8bae3ce2d 100644
>> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
>> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
>> @@ -300,6 +300,14 @@ properties:
>>       $ref: /schemas/types.yaml#/definitions/uint8-array
>>       maxItems: 4
>>   
>> +  fixed-batteries:
>> +    description: Contains references to nodes associated with battery type power
>> +      supplies powering the USB PD device. These batteries are fixed type and
> What is a "battery type power supply"? If you just link here batteries,
> then we have type for it - monitored-battery - but I doubt connector has
> direct connection to the battery.
Regarding "nodes associated with battery type power supplies", I meant 
something like a fuel guage or a charger OR platform device with 
"monitored-battery" that will manage the battery lifecycle. If I use 
monitored-battery for this, I will be restricted to only querying 1 
simple battery. Also, I don't mean PD connector device to be a fuel 
guage or charger that manages a specific battery. It should just be able 
to query any FG/Chg for the battery status to relay that info to the 
connector's port partner.

The intent of the patchset & this change is for the USB Type C protocol 
manager module (that consumes these bindings) to be able to get info 
(such as State of charge, design capacity, etc) from drivers that manage 
the battery/batteries in the system. In order for such info to propagate 
I need to hook up the references of these battery manager devices (fuel 
guages, etc.) to connector.

I have addressed the connector <-> battery question in the cover letter.


> If you mean chargers, the OF graph is already there for this and no need
> for this patch.

No I don't mean just chargers in this case. Also, I didn't follow you on 
the OF graph. Please can you explain further?


>
>> +      not hot swappable.
>> +    minItems: 1
>> +    maxItems: 4
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +
>>   dependencies:
>>     sink-vdos-v1: [ sink-vdos ]
>>     sink-vdos: [ sink-vdos-v1 ]
>> diff --git a/Documentation/devicetree/bindings/usb/maxim,max33359.yaml b/Documentation/devicetree/bindings/usb/maxim,max33359.yaml
>> index 3de4dc40b79192b60443421b557bd2fb18683bf7..66c99f0131f074f1c08e31d7481f555647e3b2f8 100644
>> --- a/Documentation/devicetree/bindings/usb/maxim,max33359.yaml
>> +++ b/Documentation/devicetree/bindings/usb/maxim,max33359.yaml
>> @@ -75,6 +75,7 @@ examples:
>>                                          PDO_FIXED(9000, 2000, 0)>;
>>                   sink-bc12-completion-time-ms = <500>;
>>                   pd-revision = /bits/ 8 <0x03 0x01 0x01 0x08>;
>> +                fixed-batteries = <&batt1 &batt2>;
> Two phandles, so two <>.

Ack. Will fix it in the next revision.

Thanks,

Amit

> Best regards,
> Krzysztof
>