linux-kernel - Re: [PATCH 2/2] pinctrl: renesas: rzg2l: Enable noise filter for GPIO interrupt input

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Date:   Wed, 20 Sep 2023 14:20:26 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-gpio@...r.kernel.org,
        Biju Das <biju.das.au@...il.com>
Subject: Re: [PATCH 2/2] pinctrl: renesas: rzg2l: Enable noise filter for GPIO
 interrupt input

On Mon, Sep 18, 2023 at 2:34 PM Biju Das <biju.das.jz@...renesas.com> wrote:

> As per RZ/G2L hardware manual Rev.1.30 section 8.7.3 GPIO Interrupt (TINT)
> and 41.4.1 Operation for GPIO function, we need to set digital noise
> filter for GPIO interrupt.
>
> This patch enables noise filter for GPIO interrupt in
> rzg2l_gpio_irq_enable() and disable it in rzg2l_gpio_irq_disable().
>
> Fixes: db2e5f21a48e ("pinctrl: renesas: pinctrl-rzg2l: Add IRQ domain to handle GPIO interrupt")
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> Tested-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Why is this called "digital noise filter" when the rest of the world calls
it "debounce"? It is a bit confusing to have differing terminology in the
kernel.

(There might be a good reason, such that the noise in question is very
different from mechanical button bounce noise.)

Is this only applicable to interrupt lines or also to GPIO lines in
general? Because I just want to ascertain that in that case
the existing binding for @PIN_CONFIG_INPUT_DEBOUNCE
and the corresponding backend call from gpio_chip() maps
to the same feature as well.

It seems hard-coded for some pins in the Renesas driver right
now but the day you make this configurable from DT please
call it debounce, if the usecase is similar.

Yours,
Linus Walleij