[PATCH] [1/5] Only scan the root bus in early PCI quirks.

Andi Kleen
2009-01-04T23:36:31Z

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>

---
arch/x86/kernel/early-quirks.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)

Index: linux-2.6.28-test/arch/x86/kernel/early-quirks.c
===================================================================
--- linux-2.6.28-test.orig/arch/x86/kernel/early-quirks.c 2008-11-24 16:42:46.000000000 +0100
+++ linux-2.6.28-test/arch/x86/kernel/early-quirks.c 2008-12-29 05:25:09.000000000 +0100
@@ -200,6 +200,12 @@
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 },
@@ -266,17 +272,17 @@

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;
+ }
}