>From the PCIe 6.0 base spec: "Generally only 64-bit BARs are good candidates, since only Legacy Endpoints are permitted to set the Prefetchable bit in 32-bit BARs, and most scalable platforms map all 32-bit Memory BARs into non-prefetchable Memory Space regardless of the Prefetchable bit value." "For a PCI Express Endpoint, 64-bit addressing must be supported for all BARs that have the Prefetchable bit Set. 32-bit addressing is permitted for all BARs that do not have the Prefetchable bit Set." "Any device that has a range that behaves like normal memory should mark the range as prefetchable. A linear frame buffer in a graphics device is an example of a range that should be marked prefetchable." The PCIe spec tells us that we should have the prefetchable bit set for 64-bit BARs backed by "normal memory". The backing memory that we allocate for a 64-bit BAR using pci_epf_alloc_space() (which calls dma_alloc_coherent()) is obviously "normal memory". Thus, set the prefetchable bit when allocating backing memory for a 64-bit BAR. Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx> --- drivers/pci/endpoint/pci-epf-core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c index e7dbbeb1f0de..20d2bde0747c 100644 --- a/drivers/pci/endpoint/pci-epf-core.c +++ b/drivers/pci/endpoint/pci-epf-core.c @@ -309,6 +309,9 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar, else epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_32; + if (epf_bar[bar].flags & PCI_BASE_ADDRESS_MEM_TYPE_64) + epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_PREFETCH; + return space; } EXPORT_SYMBOL_GPL(pci_epf_alloc_space); -- 2.44.0
