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    SubjectRe: [PATCH v2 08/10] x86/Kconfig: make CONFIG_PCI_CNB20LE_QUIRK depend on X86_32
    On Sun, Sep 11, 2022 at 10:47:09AM +0200, Mateusz Jończyk wrote:
    > I was unable to find a good description of the ServerWorks CNB20LE
    > chipset. However, it was probably exclusively used with the Pentium III
    > processor (this CPU model was used in all references to it that I
    > found where the CPU model was provided: dmesgs in [1] and [2];
    > [3] page 2; [4]-[7]).
    >
    > As is widely known, the Pentium III processor did not support the 64-bit
    > mode, support for which was introduced by Intel a couple of years later.
    > So it is safe to assume that no systems with the CNB20LE chipset have
    > amd64 and the CONFIG_PCI_CNB20LE_QUIRK may now depend on X86_32.
    >
    > Additionally, I have determined that most computers with the CNB20LE
    > chipset did have ACPI support and this driver was inactive on them.
    > I have submitted a patch to remove this driver, but it was met with
    > resistance [8].

    Only because removing the driver appeared to have no demonstrated
    benefit and risked breaking old machines.

    Making this depend on X86_32 seems plausible to me.

    > [8] Bjorn Helgaas, "Re: [PATCH] x86/pci: drop ServerWorks / Broadcom
    > CNB20LE PCI host bridge driver"
    > https://lore.kernel.org/lkml/20220318165535.GA840063@bhelgaas/T/
    >
    > Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: Borislav Petkov <bp@alien8.de>
    > Cc: Dave Hansen <dave.hansen@linux.intel.com>
    > Cc: x86@kernel.org
    > Cc: "H. Peter Anvin" <hpa@zytor.com>
    > Cc: Ira W. Snyder <ira.snyder@gmail.com>
    > Cc: Bjorn Helgaas <helgaas@kernel.org>
    > ---
    > v2: make CONFIG_PCI_CNB20LE_QUIRK depend on X86_32
    > (previously only help text and description were changed)
    > upgrade short description.
    >
    > arch/x86/Kconfig | 12 ++++++++++--
    > 1 file changed, 10 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    > index fdfe8b7e895a..31f778b0cd0b 100644
    > --- a/arch/x86/Kconfig
    > +++ b/arch/x86/Kconfig
    > @@ -2739,13 +2739,21 @@ config MMCONF_FAM10H
    > depends on X86_64 && PCI_MMCONFIG && ACPI
    >
    > config PCI_CNB20LE_QUIRK
    > - bool "Read CNB20LE Host Bridge Windows" if EXPERT
    > - depends on PCI
    > + bool "Read PCI host bridge windows from the CNB20LE chipset" if EXPERT
    > + depends on X86_32 && PCI
    > help
    > Read the PCI windows out of the CNB20LE host bridge. This allows
    > PCI hotplug to work on systems with the CNB20LE chipset which do
    > not have ACPI.
    >
    > + The ServerWorks (later Broadcom) CNB20LE was a chipset designed
    > + most probably only for Pentium III.
    > +
    > + To find out if you have such a chipset, search for a PCI device with
    > + 1166:0009 PCI IDs, for example by executing
    > + lspci -nn | grep '1166:0009'
    > + The code is inactive if there is none.
    > +
    > There's no public spec for this chipset, and this functionality
    > is known to be incomplete.
    >
    > --
    > 2.25.1
    >

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