linux-kernel - Re: [PATCH v1 1/5] PCI: PM: x86: Drop Intel MID PCI PM support

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Date:   Mon, 20 Sep 2021 12:57:27 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        x86 Maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH v1 1/5] PCI: PM: x86: Drop Intel MID PCI PM support

On Sun, Sep 19, 2021 at 10:32 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Sep 19, 2021 at 9:01 AM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> >
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Support for Intel MID platforms has mostly gone away with the SFI
> > support removal in commit 4590d98f5a4f ("sfi: Remove framework for
> > deprecated firmware"), but there are some pieces of it still in the
> > tree.  One of them is the MID PCI PM support code which gets in the
> > way of subsequent PCI PM simplifications and trying to update it is
> > rather pointless, so get rid of it completely along with the arch
> > code pieces that are only used by it.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >
> > I am going to post patches removing the rest of MID support from arch/x86/
> > and elsewhere, but that is still quite a bit of stuff and I don't want this
> > simple PCI PM series to depend on that work.
>
> This is still being used by MID with ACPI assisted (*) support.
> Hence, not ack.
>
> *) ACPI layer is provided by U-Boot and can't fulfill all possible
> features that ACPI may use in the Linux kernel.

OK, good to know.

I'm not sure how this PCI PM stuff works with ACPI.  It looks like
this relies on a specific ordering of arch_initcall() calls for
correctness which is sort of fragile.