Re: [PATCH v3 4/5] pwm: omap-dmtimer: Do not disable pwm before changing period/duty_cycle

From: Richard Cochran
Date: Thu Mar 12 2020 - 10:21:31 EST


On Thu, Mar 12, 2020 at 04:14:34PM +0530, Lokesh Vutla wrote:
> But the problem here is that inactive breaks between two periods is not desired.
> Because the pwm is used to generate a 1PPS signal and is continuously
> synchronized with PTP clock.

The 1-PPS case is the "easy" one. If the PWM is adjustable on the
fly, then people will use it with higher frequency signals.

> I am up if this can be solved generically. But updating period is very specific
> to hardware implementation. Not sure what generic solution can be brought out of
> this. Please correct me if I am wrong.

What happens today when the PWM frequency or duty cycle are changed
while the signal is enabled?

Do different PWM devices/drivers behave the same way?

Does this series change the behavior of the am335x and friends?

Thanks,
Richard