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

[Maxime Ripard <maxime.ripard@free-electrons.com>]

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Hi Linus,

On Thu, Oct 20, 2016 at 03:56:25PM +0200, Maxime Ripard wrote:
> 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@free-electrons.com> 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@free-electrons.com>
> > (...)
> > > +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.

Any comments on this?

Thanks,
Maxime

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

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