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x86: only scan the root bus in early PCI quirks 

We found a situation on Linus' machine that the Nvidia timer quirk hit on
a Intel chipset system.  The problem is that the system has a fancy Nvidia
card with an own PCI bridge, and the early-quirks code looking for any
NVidia bridge triggered on it incorrectly.  This didn't lead a boot
failure by luck, but the timer routing code selecting the wrong timer
first and some ugly messages.  It might lead to real problems on other
systems.

I checked all the devices which are currently checked for by early_quirks
and it turns out they are all located in the root bus zero.

So change the early-quirks loop to only scan bus 0.  This incidently also
saves quite some unnecessary scanning work, because early_quirks doesn't
go through all the non root busses.

The graphics card is not on bus 0, so it is not matched anymore.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andi Kleen 2009-01-09 12:17:39 -08:00 committed by Linus Torvalds
parent 4ce5f24193
commit 8659c406ad
1 changed files with 14 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
arch/x86/kernel/early-quirks.c
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@ -201,6 +201,12 @@ struct chipset {
void (*f)(int num, int slot, int func);
};
/*
* Only works for devices on the root bus. If you add any devices
* not on bus 0 readd another loop level in early_quirks(). But
* be careful because at least the Nvidia quirk here relies on
* only matching on bus 0.
*/
static struct chipset early_qrk[] __initdata = {
{ PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
PCI_CLASS_BRIDGE_PCI, PCI_ANY_ID, QFLAG_APPLY_ONCE, nvidia_bugs },
@ -267,17 +273,17 @@ static int __init check_dev_quirk(int num, int slot, int func)
void __init early_quirks(void)
{
int num, slot, func;
int slot, func;
if (!early_pci_allowed())
return;
/* Poor man's PCI discovery */
for (num = 0; num < 32; num++)
for (slot = 0; slot < 32; slot++)
for (func = 0; func < 8; func++) {
/* Only probe function 0 on single fn devices */
if (check_dev_quirk(num, slot, func))
break;
}
/* Only scan the root bus */
for (slot = 0; slot < 32; slot++)
for (func = 0; func < 8; func++) {
/* Only probe function 0 on single fn devices */
if (check_dev_quirk(0, slot, func))
break;
}
}