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

Hello,

On Sat, Feb 19, 2022 at 11:46:31AM +0500, Nikita Travkin wrote:

Uwe Kleine-König писал(а) 14.02.2022 23:43:

quoted

On Sat, Feb 12, 2022 at 09:23:42PM +0500, Nikita Travkin wrote:

quoted

+ * 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

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