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[MIPS] Fix for pci config_access on alchemy au1x000

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I've encountered a serious problem with PCI config space access on Au1x000
platforms with recent 2.6.x-kernel. With 2.4.31 the same hardware works fine.
So I was looking for the differences:

Symptoms:
- no PCI-device is seen on bootup though two or three cards are present
- lspci output is empty
- OR: lspci shows 20 times the same device
(- OR: in some slot-configurations it worked anyhow)

System(s):
1. platform with Au1500 and three PCI-devices (actually a mycable XXS1500
    with backplane for three PCI-devices)
2. platform with Au1550 and two PCI-devices (custom board)

Debugging:
I digged down to the config_access() of the au1xxx-processors in
arch/mips/pci/ops-au1000.c and switched on DEBUG.

The code of config_access() seems to be almost the same as of the
2.4.x-kernel. But the "pci_cfg_vm->addr" returned by get_vm_area(0x2000, 0)
once on booting is different. That's of course not forbidden. But the
alignment seems to be wrong. In my case, I received:

2.4.31: pci_cfg_vm->addr = c0000000
2.6.18-rc5: pci_cfg_vm->addr = c0101000

To make it short: With 2.6.x it fails on the first config-access with:
"PCI ERR detected: status 83a00356".

Fixup:
My fix is now, to use the VM_IOREMAP-flag in the get_vm_area call. This flag
seems to be introduced in mm/vmalloc.c a long time ago (in 2.6.7-bk13, I
found in gitweb).
Now, the returned address is pci_cfg_vm->addr = c0104000 and everything works
fine.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Alexander Bigga 2006-08-29 16:48:34 +02:00 committed by Ralf Baechle
parent 898d229107
commit 32136568a9
1 changed files with 1 additions and 1 deletions
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2
arch/mips/pci/ops-au1000.c
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@ -110,7 +110,7 @@ static int config_access(unsigned char access_type, struct pci_bus *bus,
if (first_cfg) {
/* reserve a wired entry for pci config accesses */
first_cfg = 0;
pci_cfg_vm = get_vm_area(0x2000, 0);
pci_cfg_vm = get_vm_area(0x2000, VM_IOREMAP);
if (!pci_cfg_vm)
panic (KERN_ERR "PCI unable to get vm area\n");
pci_cfg_wired_entry = read_c0_wired();