Re: [PATCH 1/2] pinctrl: sunxi: Add support for interrupt debouncing

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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Hi Linus,

On Thu, Oct 20, 2016 at 03:04:46PM +0200, Linus Walleij wrote:
> On Wed, Oct 19, 2016 at 11:15 AM, Maxime Ripard
> <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> 
> > The pin controller found in the Allwinner SoCs has support for interrupts
> > debouncing.
> >
> > However, this is not done per-pin, preventing us from using the generic
> > pinconf binding for that,
> 
> How typical.
> 
> > but per irq bank, which, depending on the SoC,
> > ranges from one to five.
> >
> > Introduce a device-wide property to deal with this using a nanosecond
> > resolution.
> >
> > Signed-off-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> (...)
> > +Note: For backward compatibility reasons, the hosc and losc clocks are
> > +only required if you need to use the optional
> > +allwinner,debounce-time-ns property. Any new device tree should set them.
> > +
> > +Optional properties:
> > +  - allwinner,debounce-time-ns: Array of debouncing periods in
> > +    nanoseconds. One period per irq bank found in the controller
> 
> Do you really *need* to specify this with nanosecond resolution?
>
> Else I would suggest to use microsecond resolution and just use
> the generic binding (input-debounce) but on the device node instead
> of the specific handler.

Theorically, the debouncing clock can be set at 24MHz, which means a
42ns resolution.

I've seen that the other bindings usually use microseconds, but in our
case, we can really go lower than that.

I don't really know if it makes sense though.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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