Re: [PATCH v5 2/7] pwm: pca9685: Support hardware readout

Uwe Kleine-König
2021-01-14T18:06:00Z

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Hello Clemens,

On Thu, Jan 14, 2021 at 06:16:22PM +0100, Clemens Gruber wrote:
> On Mon, Jan 11, 2021 at 09:35:32PM +0100, Uwe Kleine-König wrote:
> > My position here is: A consumer should disable a PWM before calling
> > pwm_put. The driver should however not enforce this and so should not
> > modify the hardware state in .free().
> >
> > Also .probe should not change the PWM configuration.
>
> I see. This would also allow PWMs initialized in the bootloader (e.g.
> backlights) to stay on between the bootloader and Linux and avoid
> flickering.
>
> If no one objects, I would then no longer reset period and duty cycles
> in the driver (and for our projects, reset them in the bootloader code
> to avoid leaving PWMs on after a kernel panic and watchdog reset, etc.)
>
> And if there is no pre-known state of the registers, we actually need
> the .get_state function fully implemented.

This sounds right.

Thanks
Uwe

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

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