linux-kernel - Re: [PATCH 1/2] dt-bindings: power: supply: Add Richtek RT9471 battery charger

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Message-ID: <40261b95-637a-1304-2e06-8c8ff7fc377b@linaro.org>
Date:   Fri, 12 Aug 2022 09:54:11 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     ChiYuan Huang <u0084500@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        游子馨 <alina_yu@...htek.com>,
        cy_huang <cy_huang@...htek.com>, alinayu829@...il.com,
        Linux PM <linux-pm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: power: supply: Add Richtek RT9471
 battery charger

On 12/08/2022 04:32, ChiYuan Huang wrote:
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> 於 2022年8月11日 週四 晚上10:12寫道：
>>
>> On 11/08/2022 16:41, cy_huang wrote:
>>> From: ChiYuan Huang <cy_huang@...htek.com>
>>>
>>> Add bindings for the Richtek RT9471 I2C controlled battery charger.
>>>
>>
>> Thank you for your patch. There is something to discuss/improve.
>>
>>> +properties:
>>> +  compatible:
>>> +    const: richtek,rt9471
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  ceb-gpios:
>>> +    maxItems: 1
>>
>> This looks not standard, so please provide a description.
> It's the external 'charge enable' pin that's used to control battery charging.
> The priority is higher than the register 'CHG_EN' control.
> In the word, 'b' means it's reverse logic, low to allow charging, high
> to force disable charging.

Isn't this standard enable-gpios property?

> 
> description:
>   External charge enable pin that can force control not to charge the battery.
>   Low to allow charging, high to disable charging.
> 
>>
>>> +
>>> +  wakeup-source: true
>>> +
>>> +  interrupts:
>>> +    maxItems: 1
>>> +
>>> +  interrupt-controller: true
>>> +
>>> +  "#interrupt-cells":
>>> +    const: 1
>>
>> Why a charger driver is a interrupt-controller?
> There're 32 nested IRQs from RT9471.
> The original thought is to make the user easy to bind the interrupt
> into their driver.

Bindings are not related to the driver but to hardware...

> 
> For charger driver, does it mean legacy IRQ handler is more preferred?

Who is the consumer of these interrupts? Can you show the DTS with the
interrupt consumer?

>>
>>> +
>>> +  usb-otg-vbus-regulator:
>>> +    type: object
>>> +    unevaluatedProperties: false
>>> +    $ref: /schemas/regulator/regulator.yaml#
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +  - wakeup-source
>>> +  - interrupts
>>> +  - interrupt-controller
>>> +  - "#interrupt-cells"
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    #include <dt-bindings/interrupt-controller/irq.h>
>>> +    i2c {
>>> +      #address-cells = <1>;
>>> +      #size-cells = <0>;
>>> +
>>> +      charger@53 {
>>> +        compatible = "richtek,rt9471";
>>> +        reg = <0x53>;
>>> +        ceb-gpios = <&gpio26 1 0>;
>>
>> Isn't the last value a GPIO flag? If yes, use appropriate define.
> I already specify GPIOD_OUT_LOW in the gpiod_request flag.

It is not related to the DTS. Anyway writing "low" for a meaning of high
is not correct usually...

> Do I need to convert the gpio request code to GPIOD_OUT_HIGH,
> and specify here as GPIO_ACTIVE_LOW?

You need to properly describe the hardware. The polarity of logical
signal is defined by DTS, not by driver. It does not make sense to do it
in driver. What if on some board the signal is inverted?

Best regards,
Krzysztof