linux-kernel - Re: [PATCH] PCI/ASPM: Should not report ASPM support to BIOS if FADT indicates ASPM is unsupported

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Date:   Fri, 15 Jul 2022 14:56:40 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Manyi Li <limanyi@...ontech.com>
Cc:     Matthew Garrett <mjg59@...f.ucam.org>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Saheed O. Bolarinwa" <refactormyself@...il.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rajat Jain <rajatja@...gle.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Vidya Sagar <vidyas@...dia.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] PCI/ASPM: Should not report ASPM support to BIOS if FADT
 indicates ASPM is unsupported

On Fri, Jul 15, 2022 at 2:32 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Fri, Jul 15, 2022 at 12:23 PM Manyi Li <limanyi@...ontech.com> wrote:
> >
> >
> >
> > On 2022/7/15 17:32, Matthew Garrett wrote:
> > > On Fri, Jul 15, 2022 at 05:19:25PM +0800, Manyi Li wrote:
> > >>
> > >>
> > >> On 2022/7/15 16:29, Matthew Garrett wrote:
> > >>> On Fri, Jul 15, 2022 at 03:40:36PM +0800, Manyi Li wrote:
> > >>>
> > >>>> Please see the details of this issus:
> > >>>> https://bugzilla.kernel.org/show_bug.cgi?id=216245
> > >>>
> > >>> Hmm. The only case where changing aspm_support_enabled to false should
> > >>> matter is in pcie_aspm_init_link_state(), where it looks like we'll
> > >>> potentially rewrite some registers even if aspm_disabled is true. I
> > >>> think in theory we shouldn't actually modify anything as a result, and
> > >>> the lspcis from the bug don't show any ASPM values having changed, but I
> > >>> don't trust Realtek hardware in the general case so maybe it gets upset
> > >>> here? If the proposed patch is to just set aspm_support_enabled to false
> > >>> when we see the FADT bit set then I think this is fine.
> > >>>
> > >>
> > >> "aspm_support_enabled" alse be used in calculate_support():
> > >> if (pcie_aspm_support_enabled())
> > >>      support |= OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT;
> > >> When set OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT, cause this AER
> > >> issue. I want don't set OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT when
> > >> we see the FADT bit set.
> > >
> > > Oh hm. Are you sure it's the OSC call that breaks it? I have some
> >
> > I don't sure.
> >
> > > recollection that I verified the behaviour of Windows here, but it's
> > > been over 10 years since I touched this so I could well be wrong. I can
> > > try to set up a test env to verify the behaviour of Windows when it
> > > comes to _OSC if the FADT says ASPM is unsupported.
> > >
> > but, I did a test，this modification also solves the problem:
> >
> > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > index d57cf8454b93..b3ea8e886d7c 100644
> > --- a/drivers/acpi/pci_root.c
> > +++ b/drivers/acpi/pci_root.c
> > @@ -494,8 +494,8 @@ static u32 calculate_support(void)
> >          support |= OSC_PCI_HPX_TYPE_3_SUPPORT;
> >       if (pci_ext_cfg_avail())
> >               support |= OSC_PCI_EXT_CONFIG_SUPPORT;
> > -    if (pcie_aspm_support_enabled())
> > -            support |= OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT;
> > +//  if (pcie_aspm_support_enabled())
> > +//          support |= OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT;
> >       if (pci_msi_enabled())
> >               support |= OSC_PCI_MSI_SUPPORT;
> >       if (IS_ENABLED(CONFIG_PCIE_EDR))
> >
> > This issue occur in the Notebook: ASUSTeK COMPUTER INC. X456UJ
> > (ASUS-NotebookSKU) Notebook
> >
> > log "AER: Corrected error received: 0000:00:1c.5" is in the device:
> > 00:1c.5 PCI bridge [0604]: Intel Corporation Sunrise Point-LP PCI
> > Express Root Port #6 [8086:9d15] (rev f1)
>
> So it looks like the BIOS sets ACPI_FADT_NO_ASPM and then happily
> grants control of ASPM via _OSC.  That's somewhat contradictory.
>
> I would rather look at adjusting pcie_aspm_sanity_check() to this case
> instead of wholesale changing the way _OSC is handled at the host
> bridge level.

Actually, if ACPI_FADT_NO_ASPM is set in the FADT, aspm_disabled
should be set already when negotiate_os_control() runs?

Can you please check if this is the case on the affected system?

In that case, negotiate_os_control() doesn't need to set *no_aspm,
because it only causes pcie_no_aspm() to be called, but it should have
been called already.