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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 10 Jun 2021 13:14:49 +0300
Message-ID: <CAHp75VeYy0tyP-OLZX5dbYFZM1C_K5eALo64_nb4rSvH7-93FA@mail.gmail.com>
Subject: Re: [rfc, PATCH v1 0/7] PCI: introduce p2sb helper
To:     Henning Schild <henning.schild@siemens.com>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Jean Delvare <jdelvare@suse.de>,
        Lee Jones <lee.jones@linaro.org>,
        Tan Jui Nee <jui.nee.tan@intel.com>,
        Jim Quinlan <james.quinlan@broadcom.com>,
        Jonathan Yong <jonathan.yong@intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-i2c <linux-i2c@vger.kernel.org>,
        linux-pci <linux-pci@vger.kernel.org>,
        Jean Delvare <jdelvare@suse.com>,
        Peter Tyser <ptyser@xes-inc.com>,
        Hans de Goede <hdegoede@redhat.com>
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On Thu, Jun 10, 2021 at 12:14 PM Henning Schild
<henning.schild@siemens.com> wrote:
>
> Am Mon, 8 Mar 2021 14:20:13 +0200
> schrieb Andy Shevchenko <andriy.shevchenko@linux.intel.com>:
>
> > There are a few users and even at least one more is coming
> > that would like to utilize p2sb mechanisms like hide/unhide
> > a device from PCI configuration space.
> >
> > Here is the series to deduplicate existing users and provide
> > a generic way for new comers.
> >
> > It also includes a patch to enable GPIO controllers on Apollo Lake
> > when it's used with ABL bootloader w/o ACPI support.
>
> That bit is especially interesting. Making pinctl*lake initialize when
> ACPI IDs are missing and p2sb is hidden.
>
> However i have seen pinctl-broxton get confused because it was trying
> to come up twice on a system that has the ACPI entries. Once as
> "INT3452" and second as "apollolake-pinctrl". They should probably
> mutually exclude each other. And the two different names for "the
> same"? thing make it impossible to write a driver using those GPIOs.

Then it's clearly told that BIOS provides confusing data, it exposes
the ACPI device and hides it in p2sb, how is it even supposed to work?

I consider only these are valid:
 - ACPI device is provided and it's enabled (status = 15) => work with
ACPI enumeration
 - no ACPI device provided and it's hidden or not by p2sb => work via board file
 - no ACPI device provided and no device needed / present => no driver is needed

> Unless it would try and look up both variants or not looking up with
> gpiochip.label.
>
> I would also need that "enable GPIO w/o ACPI" for skylake.

Not a problem to add a platform driver name there or actually for all
of the Intel pin control drivers (depends what suits better to the
current design).

>  I think it
> would be generally useful if the GPIO controllers would be enabled not
> depending on ACPI, and coming up with only one "label" to build on top.

I didn't get what 'label' means here...

> > Please, comment on the approach and individual patches.
> >
> > (Since it's cross subsystem, the PCI seems like a main one and
> >  I think it makes sense to route it thru it with immutable tag
> >  or branch provided for the others).


-- 
With Best Regards,
Andy Shevchenko