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

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

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On Mon, Nov 07, 2016 at 10:40:04AM +0100, Linus Walleij wrote:
> On Wed, Nov 2, 2016 at 8:51 PM, Maxime Ripard
> <maxime.ripard@free-electrons.com> wrote:
> > On Thu, Oct 20, 2016 at 03:56:25PM +0200, Maxime Ripard wrote:
> >> 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?
> 
> My first thought: can you atleast support both?
> 
> My preference would be to add the standard binding and use that,
> and the day you realize that "howli mackarowli, this thingofabob
> actually needs to specify with nanosecond precision" then we
> could add the nanosecond granularity binding?

That works for me. I'll resend the patch.

Thanks!
Maxime

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

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