From: Patrick Rudolph Date: Wed, 26 Feb 2025 13:56:42 +0000 (+0100) Subject: pci_auto: Downgrade prefetch if necessary X-Git-Tag: v2025.07-rc1~18^2~54^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=699baa63ddcabe141adf3305d61f7b2a0d2de5db;p=pandora-u-boot.git pci_auto: Downgrade prefetch if necessary 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 --- 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;