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 14:32:16 +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 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.