linux-kernel - Re: [PATCH v1 1/1] x86/platform: Increase maximum GPIO number for X86

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Date:   Mon, 16 Aug 2021 15:25:13 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v1 1/1] x86/platform: Increase maximum GPIO number for X86_64

On Fri, Aug 6, 2021 at 4:44 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> By default the 512 GPIOs is a maximum on any x86 platform.
> With, for example, Intel Tiger Lake-H the SoC based controller
> occupies up to 480 pins. This leaves only 32 available for
> GPIO expanders or other drivers, like PMIC. Hence, bump the
> maximum GPIO number to 1024 for X86_64 and leave 512 for X86_32.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  arch/x86/Kconfig | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 45962aaf2b2c..495ed6229b52 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -340,6 +340,19 @@ config NEED_PER_CPU_PAGE_FIRST_CHUNK
>  config ARCH_HIBERNATION_POSSIBLE
>         def_bool y
>
> +# The GPIO number here must be sorted by descending number. In case of
> +# a multiplatform kernel, we just want the highest value required by the
> +# selected platforms.
> +config ARCH_NR_GPIO
> +       int
> +       default 1024 if X86_64
> +       default 512 if X86_32
> +       default 0

Wouldn't

default 1024 if X86_64
default 512

be sufficient?

It's either X86_64 or X86_32 anyway AFAICS.

> +       help
> +         Maximum number of GPIOs in the system.
> +
> +         If unsure, leave the default value.
> +
>  config ARCH_SUSPEND_POSSIBLE
>         def_bool y
>
> --