Hi Linus,
Am Donnerstag, 24. Mai 2018, 10:28:44 CEST schrieb Linus Walleij:
> On Wed, May 23, 2018 at 5:12 PM, Heiko Stübner <heiko@xxxxxxxxx> wrote:
> > So the gpio controller should definitly also be a subnode.
> >
> > The gpio in question is called "mute", so I'd think the gpio-syscon driver
> > should just define a "rockchip,rk3328-gpio-mute" compatible and contain
> > all the register voodoo in the driver itself and not define it in the dt.
> >
> > So it should probably look like
> >
> > grf: syscon at ff100000 {
> >
> > compatible = "rockchip,rk3328-grf", "syscon", "simple-mfd";
> >
> > [all the other syscon sub-devices]
> >
> > gpio_mute: gpio-mute {
> >
> > compatible = "rockchip,rk3328-gpio-mute";
> > gpio-controller;
> > #gpio-cells = <2>;
> >
> > };
>
> I'm sceptic.
>
> That doesn't sound like "general purpose input output" at all.
>
> It sounds like special purpose, for a mute button.
>
> Does it use IRQ? I would recommend implementing
> drivers/input/keyboard/syscon-keys.c in the same vein
> as drivers/leds/leds-syscon.c so you can avoid indirection
> through GPIO for no good reason at all.
To quote Levin from the other mail:
--------
The "mute" pin is a output only GPIO, which is already supported by
setting flags in the gpio-syscon
driver. And yes, this pin has a defined function, but can also be used
for general purpose operation.
--------
So to summarize, the documentation calls it "mute", but it is usable as
a general pin, which is the reason Levin is working on it - because on his
board this pin is used to switch between two voltages (aka a gpio-regulator)
for the sdmmc controller [3.3V + 1.8V].
Available pin settings are output-enable + of course the high/low setting
and I think I remember there is even a pull setting for it in the GRF
somewhere - but my memory might be fuzzy here.
Heiko
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