Re: [rfc, PATCH v1 0/7] PCI: introduce p2sb helper

Andy Shevchenko
2021-06-10T10:16:22Z

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