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

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Date:   Mon, 16 Aug 2021 16:35:38 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
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 Mon, Aug 16, 2021 at 03:25:13PM +0200, Rafael J. Wysocki wrote:
> 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.

Thanks for review, my answers below.

> > +# 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.

I guess so.

> > +       help
> > +         Maximum number of GPIOs in the system.
> > +
> > +         If unsure, leave the default value.

Btw, what do you think. do we need comment above and help text here? I copied
these from ARM, but I'm not sure it would be useful on x86 as much.


-- 
With Best Regards,
Andy Shevchenko