Legacy PCI devices, like qemu's Bochs VGA device, are allowed to have
prefetchable 32-bit BARs, while PCIe devices are not allowed to have
32-bit prefetchable BARs. Typically prefetchable BARs are 64-bit and
typically the prefetch MMIO window is also 64-bit and placed above
4GiB, as it's the case on qemu sbsa-ref.
Currently the U-Boot code assumes that prefetchable BARs are
64-bit BARs and always tries to assign them into the prefetch
MMIO window.
When a 32-bit BAR is marked as prefetch, but the prefetch area is
not within the first 4GiB of the address space, then downgrade the
BAR and place it in the non-prefetch MMIO window.
For prefetch BARs there's no downside on being placed in non prefetch
MMIO areas, besides the possible slower performance when a driver tries
to map it Write-Combine.
TEST: Fixes pci_auto on QEMU sbsa-ref fails to autoconfigure BAR0.
Signed-off-by: Patrick Rudolph <patrick.rudo...@9elements.com>
---
drivers/pci/pci_auto.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/pci_auto.c b/drivers/pci/pci_auto.c
index 90f81886445..e68e31a8227 100644
--- a/drivers/pci/pci_auto.c
+++ b/drivers/pci/pci_auto.c
@@ -107,7 +107,8 @@ static void dm_pciauto_setup_device(struct udevice *dev,
}
if (prefetch &&
- (bar_response & PCI_BASE_ADDRESS_MEM_PREFETCH))
+ (bar_response & PCI_BASE_ADDRESS_MEM_PREFETCH) &&
+ (found_mem64 || prefetch->bus_lower <
0x100000000ULL))
bar_res = prefetch;
else
bar_res = mem;
--
2.48.1
