[PATCH v8 3/6] dt-bindings: pwm: airoha: Add EN7581 pwm

[Benjamin Larsson]

On 22/10/2024 23:17, Rob Herring wrote:
> So how is the PWM involved? I'm going to need a picture.
>
> If this external shift register chip can be attached to any PWM and
> clock providers, then perhaps it needs to be its own node with a 'pwms'
> property and clock source.
>
> I would suggest you go back to the version without these properties
> and that I already reviewed, then discuss adding them separately.
>
> Rob

Hi, to answer your question. The shift register is not attached to any 
PWM output, there is a specific pin function (mux) that the shift 
register needs to be connected to for the (pwm capable) gpio hardware to 
be able to drive it. If that is done the shift register pins can output 
pwm signals. So if you are low on gpio pins for leds you can connect a 
shift register and serialize the state of leds connected to the shift 
register.

You can even connect several shift registers chips in a chain with a 
total of 17 outputs. The kernel already has support to drive shift 
register leds but with pwm you can do fancy stuff like dimming and color 
mixing.

MvH

Benjamin Larsson