[PATCHv2][AWS-{F, G}] UBUNTU: SAUCE: arm64: Enable PCI write-combine resources under sysfs

Kamal Mostafa kamal at canonical.com
Wed Oct 7 20:11:20 UTC 2020

From: Clint Sbisa <csbisa at amazon.com>

BugLink: https://bugs.launchpad.net/bugs/1893817

Using write-combine is crucial for performance of PCI devices where
significant amounts of transactions go over PCI BARs.

arm64 supports write-combine PCI mappings, so the appropriate define
has been added which will expose write-combine mappings under sysfs
for prefetchable PCI resources.

Signed-off-by: Clint Sbisa <csbisa at amazon.com>
Reference: https://lore.kernel.org/linux-pci/20200831151827.pumm2p54fyj7fz5s@amazon.com/
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>                             
Acked-by: Andrea Righi <andrea.righi at canonical.com>                             
 arch/arm64/include/asm/pci.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h
index 70b323cf8300..b33ca260e3c9 100644
--- a/arch/arm64/include/asm/pci.h
+++ b/arch/arm64/include/asm/pci.h
@@ -17,6 +17,7 @@
 #define pcibios_assign_all_busses() \
+#define arch_can_pci_mmap_wc() 1
 extern int isa_dma_bridge_buggy;

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