[PATCH 6/6] arm64: defconfig: Enable Renesas DA9062 defconfig

[Geert Uytterhoeven]

Hi Biju,

On Mon, Dec 11, 2023 at 9:32 AM Biju Das <biju.das.jz at bp.renesas.com> wrote:
> > -----Original Message-----
> > From: Geert Uytterhoeven <geert at linux-m68k.org>
> > Sent: Monday, December 11, 2023 8:20 AM
> > Subject: Re: [PATCH 6/6] arm64: defconfig: Enable Renesas DA9062 defconfig
> >
> > On Sun, Dec 10, 2023 at 10:50 AM Biju Das <biju.das.jz at bp.renesas.com>
> > wrote:
> > > > -----Original Message-----
> > > > From: Geert Uytterhoeven <geert at linux-m68k.org>
> > > > Sent: Friday, December 1, 2023 3:42 PM
> > > > Subject: Re: [PATCH 6/6] arm64: defconfig: Enable Renesas DA9062
> > > > defconfig
> > > >
> > > > On Fri, Dec 1, 2023 at 4:02 PM Biju Das <biju.das.jz at bp.renesas.com>
> > > > wrote:
> > > > > > From: Geert Uytterhoeven <geert at linux-m68k.org> On Fri, Dec 1,
> > > > > > 2023 at 12:09 PM Biju Das <biju.das.jz at bp.renesas.com>
> > > > > > wrote:
> > > > > > > Enable the config for the Renesas DA9062 PMIC and RTC, as it
> > > > > > > is populated on RZ/G2UL SMARC EVK.
> > > > > > >
> > > > > > > Signed-off-by: Biju Das <biju.das.jz at bp.renesas.com>
> > > > > >
> > > > > > Thanks for your patch!
> > > > > >
> > > > > > LGTM, but I would have expected (at least)
> > > > > >
> > > > > >     CONFIG_INPUT_DA9063_ONKEY=m
> > > > > >
> > > > > > too, cfr. my comments on patch 5/6.
> > > > >
> > > > > I have tested this, but I get "da9063-onkey da9062-onkey: error -
> > ENXIO:
> > > > IRQ ONKEY not found"
> > > > > So, I won't be able to test onkey events. So plaaning to disable
> > > > > this
> > > > node.
> > > >
> > > > Indeed, currently drivers/input/misc/da9063_onkey.c requires an
> > > > interrupt to function.  I wonder if it can be made to work using a
> > > > timer and pure polling...
> > >
> > > Yes, that is possible by either adding a debugfs to enable polling for
> > testing.
> > >
> > > Or
> > >
> > > a device tree property for adding poll delay, so that one can have
> > polling support to test onkey driver.
> >
> > I would go for the latter, cfr. poll-interval in
> > Documentation/devicetree/bindings/input/gpio-keys.yaml.
> >
> > > Basically, on a production system we should avoid polling as it
> > unnecessarily wakeup the system.
> >
> > Wouldn't polling (by Linux) only happen when the system is already awake?
>
> IIUC, That is an overhead. If there is no load, system goes to suspend mode and
> the timer for the polling (SCAN keys) will wakeup the system and same
> process repeats. If we have a PMIC IRQ, this won't happen.

Ah, you mean idle. Yes, that does incur a (small) overhead (I guess
there are other timers running, too).
I don't think any timer runs when the system is suspended.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds