fade_led sample doesn't work with pwm_nrfx driver

[JoeHut]

I tried to change the fade_led sample to support the pwm_nrfx driver introduced in v1.13. This results in a fail to set the pwm period.
Reason: The default in the pwm_nrfx driver for prescalers is 0, which means that a 16MHz clock is applied. The sample therefore sets a period of 320,000 cycles but the driver only supports max 32,768 cycles, so the clock has to be reduced to a frequency of 1MHz to make the sample work. This seems to be odd since the software based pwm driver supports 50us as period with a 16MHz clock.

My question basically is just, whether this is intended and the prescaler should be adjusted if support for the pwm_nrfx driver is added to the samples or if there is something wrong.

[nashif]

@carlescufi can you please assign?

[carlescufi]

Added @pdunaj as well since we have similar functionality downstream

[anangl]

This 32,767 cycles limit is no longer present in the pwm_nrfx driver. Since commit 2d5ea10, the PWM prescaler is modified accordingly to find a fit for the requested period length, precisely this part of code does this.
I think this issue can be closed as resolved by #11726.

[anangl]

Fixed by #11726.