[tip: x86/urgent] x86/Kconfig: Make CONFIG_PCI_CNB20LE_QUIRK depend on X86_32

["tip-bot2 for Mateusz Jończyk" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     d9f87802676bb23b9425aea8ad95c76ad9b50c6e
Gitweb:        https://git.kernel.org/tip/d9f87802676bb23b9425aea8ad95c76ad9b50c6e
Author:        Mateusz Jończyk <mat.jonczyk@o2.pl>
AuthorDate:    Fri, 21 Mar 2025 21:48:48 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 22 Mar 2025 08:08:57 +01:00

x86/Kconfig: Make CONFIG_PCI_CNB20LE_QUIRK depend on X86_32

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].

[1] Jim Studt, Re: Problem with ServerWorks CNB20LE and lost interrupts
    Linux Kernel Mailing List, https://lkml.org/lkml/2002/1/11/111

[2] RedHat Bug 665109 - e100 problems on old Compaq Proliant DL320
    https://bugzilla.redhat.com/show_bug.cgi?id=665109

[3] R. Hughes-Jones, S. Dallison, G. Fairey, Performance Measurements on
    Gigabit Ethernet NICs and Server Quality Motherboards,
    http://datatag.web.cern.ch/papers/pfldnet2003-rhj.doc

[4] "Hardware for Linux",
    Probe #d6b5151873 of Intel STL2-bd A28808-302 Desktop Computer (STL2)
    https://linux-hardware.org/?probe=d6b5151873

[5] "Hardware for Linux", Probe #0b5d843f10 of Compaq ProLiant DL380
    https://linux-hardware.org/?probe=0b5d843f10

[6] Ubuntu Forums, Dell Poweredge 2400 - Adaptec SCSI Bus AIC-7880
    https://ubuntuforums.org/showthread.php?t=1689552

[7] Ira W. Snyder, "BISECTED: 2.6.35 (and -git) fail to boot: APIC problems"
    https://lkml.org/lkml/2010/8/13/220

[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>
Signed-off-by: David Heideberg <david@ixit.cz>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250321-x86_x2apic-v3-6-b0cbaa6fa338@ixit.cz
---
 arch/x86/Kconfig | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a079ecf..1090eda 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2929,13 +2929,21 @@ 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.