Re: [v2 2/2] pwm: Add Aspeed ast2600 PWM support

From: Uwe Kleine-König
Date: Mon May 03 2021 - 02:24:01 EST


your second reply is nearly identical to the first. It would be helpful
to only write new stuff in new mail. I think there is only a single new
paragraph that I will reply to here.

On Mon, May 03, 2021 at 05:57:23AM +0000, Billy Tsai wrote:
> On 2021/4/27, 4:44 AM,Uwe Kleine-Königwrote:
> > Also please round down in the division to never provide a duty_cycle
> > bigger than the requested vaule. Also you have to use the actually used
> > period as divider, not state->period.
> I don’t think that I should use the actually used period as divider.
> The state->duty_cycle is relative with state->period, not the actual period
> if I use the actual period the precision of the duty cycle may lose.

The strategy you should implement in .apply() is: Pick the biggest
period that is not bigger than the requested period. With that period
pick the biggest duty_cycle that is not bigger than the requested

As the actual period might be smaller than state->period, dividing by
the latter yields a result that might be too small.

See commit 8035e6c66a5e98f098edf7441667de74affb4e78 (currently in next)
for a similar example.

Best regards

Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | |

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