Re: [PATCH RESEND 2/2] gpio: mvebu: Allow to use non-default PWM counter

From: Aditya Prayoga
Date: Wed Aug 08 2018 - 07:40:23 EST

On Mon, Aug 6, 2018 at 8:53 PM Andrew Lunn <andrew@xxxxxxx> wrote:
> On Mon, Aug 06, 2018 at 10:29:16AM +0800, Aditya Prayoga wrote:
> > On multiple PWM lines, if the other PWM counter is unused, allocate it
> > to next PWM request. The priority would be:
> > 1. Default counter assigned to the bank
> > 2. Unused counter that is assigned to other bank
> > 3. Fallback to default counter
> >
> > For example on second bank there are three PWM request, first one would
> > use default counter (counter B), second one would try to use counter A,
> > and the third one would use counter B.
> Hi Aditya
> There are only two PWM counters for all the GPIO lines. So you cannot
> support 3 PWM requests. You have to enforce a maximum of two PWMs.
> When i implemented this PWM code, i only needed one PWM. So it took
> the easy option. GPIO bank 0 uses counter A, GPIO bank1 uses counter
> B. For the hardware you have, this is not sufficient, so you need to
> generalise this. Any PWM can use any counter, whatever is available
> when the PWM is requested.

Hi Andrew

Understood. I will change it in next version.

> Rather than have a linked list of PWM, i think it would be better to
> have a static array of two mvebu_pwm structures. Index 0 uses counter
> A, index 1 uses counter B. You can then keep with the concept of
> pwm->pgiod != NULL means the counter is in use. The request() call can
> then find an unused PWM, set pwm->gpiod, and point mvchip->mvpwm to
> one of the two static instances.

That was my initial idea to use static array but then I thought maybe
I could generalise it for future device by using linked list.


> Andrew