Messages in this thread | | | From | Andy Shevchenko <> | Date | Fri, 5 Jun 2020 12:33:01 +0300 | Subject | Re: [PATCH v4 05/11] pwm: add support for sl28cpld PWM controller |
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On Fri, Jun 5, 2020 at 11:51 AM Lee Jones <lee.jones@linaro.org> wrote: > On Thu, 04 Jun 2020, Michael Walle wrote:
...
> > + cycle = state->duty_cycle * config->max_duty_cycle; > > + do_div(cycle, state->period); > > Forgive my ignorance (I'm new here!), but what are these 2 lines > doing? Here we are multiplying the current duty_cycle with the > maximum value, then dividing by the period. > > So in the case of PWM_MODE_1KHZ with a 50% duty cycle, you'd have: > > (500000 * 0x20[16]) / 1000000 = [0x10]16 > > Thus, the above gives as a proportional representation of the maximum > valid value for placement into the cycle control register(s), right? > > Either way (whether I'm correct or not), I think it would be nice to > mention this in a comment. Maybe even clarify with a simple example.
IIRC PWM has a helper for that (to calc period based on PWM state and new duty cycle %).
-- With Best Regards, Andy Shevchenko
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