Re: [PATCH v5 2/2] pwm: Add clock based PWM output driver

[Uwe Kleine-König]

Hello,

On Sat, Feb 19, 2022 at 11:46:31AM +0500, Nikita Travkin wrote:
> Uwe Kleine-König писал(а) 14.02.2022 23:43:
> > On Sat, Feb 12, 2022 at 09:23:42PM +0500, Nikita Travkin wrote:
> >> + * Limitations:
> >> + * - Glitches are possible when new pwm state is applied.
> >> + * - Due to the fact that exact behavior depends on the underlying
> >> + *   clock driver, various limitations are possible.
> >> + * - Period depends on the clock and, in general, not guaranteed.
> > 
> > This sentence is broken.
> > 
> 
> Here what I mean is that the clock driver might e.g. have a lookup table
> for some rates and will only set one close to the requested ones.
> (Extreme scenario is that only one rate is allowed in the lookup table,
> which is a real possibility for some platforms that I think this driver
> will be used with, the lookup may need to be changed for those clocks)
> 
> I will reword this like:
> 
>   Some clock drivers may only pick the closest available rate
>   and not the exact requested one. Because of this, exact period
>   is not guaranteed.

That there is no exact match is quite normal also for dedicated PWM
HW blocks. So I think the second item in your list is good enough to
cover the non-existing guaranteed for period and glitches.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
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