linux-kernel - Re: [PATCH] PCI/APCI: Move acpi_pci_osc_support() check to negotiation phase

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Message-ID: <CAJZ5v0iR-iar8BGwM7QgFEkqeRkZ=qn1PrKW0yxrERjDViUjaA@mail.gmail.com>
Date:   Mon, 7 Jun 2021 16:18:35 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI/APCI: Move acpi_pci_osc_support() check to
 negotiation phase

On Mon, Jun 7, 2021 at 4:14 PM Joerg Roedel <jroedel@...e.de> wrote:
>
> On Mon, Jun 07, 2021 at 02:56:24PM +0200, Rafael J. Wysocki wrote:
> > On Fri, Jun 4, 2021 at 7:09 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > >  If either "pcie_ports_disabled" or Linux doesn't support everything in
> > > ACPI_PCIE_REQ_SUPPORT, we will never evaluate _OSC at all, so
> > > the platform won't know that Linux has OSC_PCI_SEGMENT_GROUPS_SUPPORT,
> > > OSC_PCI_HPX_TYPE_3_SUPPORT, OSC_PCI_EXT_CONFIG_SUPPORT, etc.
> >
> > Right.
>
> Thanks Bjorn and Rafael. So I think the important thing to do is to
> issue at least one _OSC call even when Linux is not trying to take
> control of anything.
>
> I look into a clean way to do this and get the kernel messages right.
> One thing to change is probably only calculating 'control' if
> !pcie_ports_disabled in negotiate_os_control().

Please also see
https://lore.kernel.org/linux-acpi/93d783c4-4468-023b-193e-3fc6eca35445@redhat.com/
for possible clashes etc.