Re: [v6 1/4] dt-bindings: pwm: Add ASPEED PWM Control documentation
From: Krzysztof Kozlowski <hidden>
Date: 2023-06-08 09:26:14
Also in:
linux-aspeed, linux-devicetree, linux-doc, linux-hwmon, linux-pwm, lkml
On 08/06/2023 10:57, Billy Tsai wrote:
On 08/06/2023 10:21, Billy Tsai wrote:
>> On 08/06/2023 09:47, Billy Tsai wrote:
>> >>
>> >> >> +
>> >> >> +allOf:
>> >> >> + - $ref: pwm.yaml#
>> >> >> +
>> >> >> +properties:
>> >> >> + compatible:
>> >> >> + enum:
>> >> >> + - aspeed,ast2600-pwm
>> >> >> +
>> >> >> + "#pwm-cells":
>> >> >> + const: 3
>> >>
>> >> > 3 cells? For one PWM? What are they?
>> >>
>> >> channel, period and polarity.
>>
>> > Don't cut my responses. You wrote you have one PWM output, so only one
>> > channel. What do you put then in the channel?
>>
>> You need to put 0 in the cell of the channel, the example of the dts usage will like following:
> If you always put 0 isn't this a proof that it's wrong?
No, if your PWM controller only has one pwm output, then it should only be configured as 0.
This is the usage of the pwm-cells property.
https://github.com/torvalds/linux/blob/master/drivers/pwm/core.c#L129-L158This is only when you use generic of_xlate. You do not have to use generic of_xlate if it does not suite you. Again you speak about the drivers, but we talk about bindings: https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/pwm/pwm.txt#L13 "controller specific"
https://github.com/torvalds/linux/blob/master/include/linux/pwm.h#LL299C20-L299C20 All of the pwm driver with npwm = 1 will has the same usage.
So it seems many simplified their drivers... Best regards, Krzysztof _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel