[PATCH 2/5] pwm: kona: Introduce Kona PWM controller support

[Tim Kryger]

On Tue, Nov 26, 2013 at 1:45 AM, Thierry Reding
<thierry.reding at gmail.com> wrote:
> On Mon, Nov 25, 2013 at 05:38:44PM -0800, Tim Kryger wrote:

> Okay, that's fine then. Do you have a pointer to that documentation?

Unfortunately the documentation is not publicly available at the moment.

>> The hardware is always enabled and at best can be be configured to
>> operate at zero duty.
>
> What good are the PWMOUT_ENABLE bits then? Is that really only used for
> triggering updates? That's what another comment suggests, but if so, can
> the comment in kona_pwmc_apply_settings() be extended to mention that?

The guidance from the documentation is to treat the enable bits as a trigger.

Sure I can expand the comment to try and make this more clear.

>> The settings in HW may have already been triggered and might not be
>> what you want.
>>
>> For example:
>>
>> /sys/class/pwm/pwmchip0/pwm1# echo 1 > enable
>> /sys/class/pwm/pwmchip0/pwm1# echo 5000 > period
>> /sys/class/pwm/pwmchip0/pwm1# echo 2000 > duty_cycle
>> /sys/class/pwm/pwmchip0/pwm1# echo 0 > enable
>> /sys/class/pwm/pwmchip0/pwm1# echo 1 > enable
>
> I'm not exactly sure what this is supposed to demonstrate.

The computation has to be performed for every operation except the disable.

> All of that said, I wasn't able to dig up a normative policy and either
> of your proposed alternatives do exist in the kernel, so I withdraw any
> objections regarding MODULE_AUTHOR. Take your pick.

Thanks