2002-10-03 17:09:54

by Ivan Kokshaysky

[permalink] [raw]
Subject: [patch 2.5.40] PCI: probing read-only BARs

Some pci devices may have base address registers locked with non-zero values.
- AGP aperture BAR of AMD-7xx host bridges: if the AGP window disabled,
this BAR is read-only and read as 0x00000008;
- BAR0-4 of ALi IDE controllers can be non-zero and read-only.
Obviously, we can't calculate correct size of the respective region in
this case (for AMD AGP window we'll get 4 GB resource - ouch).
So I think that we should ignore r/o BARs (let the device specific
fixups deal with them if needed).
Patch appended (note that extra write(0)/read-back pair is required,
as the BAR might be programmed with all 1s).


--- 2.5.40/drivers/pci/probe.c Sat Sep 28 01:49:10 2002
+++ linux/drivers/pci/probe.c Thu Oct 3 13:26:41 2002
@@ -46,7 +46,7 @@ static u32 pci_size(u32 base, unsigned l
static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
unsigned int pos, reg, next;
- u32 l, sz;
+ u32 l, l0, sz;
struct resource *res;

for(pos=0; pos<howmany; pos = next) {
@@ -55,10 +55,12 @@ static void pci_read_bases(struct pci_de
res->name = dev->name;
reg = PCI_BASE_ADDRESS_0 + (pos << 2);
pci_read_config_dword(dev, reg, &l);
+ pci_write_config_dword(dev, reg, 0);
+ pci_read_config_dword(dev, reg, &l0);
pci_write_config_dword(dev, reg, ~0);
pci_read_config_dword(dev, reg, &sz);
pci_write_config_dword(dev, reg, l);
- if (!sz || sz == 0xffffffff)
+ if (!sz || sz == 0xffffffff || sz == l0)
if (l == 0xffffffff)
l = 0;