Re: [PATCH v10 3/4] pwm: add microchip soft ip corePWM driver

Uwe Kleine-König
2022-09-30T09:13:37Z

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On Mon, Sep 19, 2022 at 03:29:19PM +0100, Conor Dooley wrote:
> Hey Uwe,
>
> On Mon, Sep 19, 2022 at 03:50:08PM +0200, Uwe Kleine-König wrote:
> > On Mon, Sep 19, 2022 at 01:53:56PM +0100, Conor Dooley wrote:
> > > Because I was running into conflicts between the reporting here and some
> > > of the checks that I have added to prevent the PWM being put into an
> > > invalid state. On boot both negedge and posedge will be zero & this was
> > > preventing me from setting the period at all.
> >
> > I don't understood that.
>
> On startup, (negedge == posedge) is true as both are zero, but the reset
> values for prescale and period are actually 0x8. If on reset I try to
> set a small period, say "echo 1000 > period" apply() returns -EINVAL
> because of a check in the pwm core in pwm_apply_state() as I am
> attempting to set the period to lower than the out-of-reset duty cycle.

You're supposed to keep the period for pwm#1 untouched while configuring
pwm#0 only if pwm#1 already has a consumer. So if pwm#1 isn't requested,
you can change the period for pwm#0.

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |

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