[PATCH][AWS-B] UBUNTU: SAUCE: arm64: Enable PCI write-combine resources under sysfs

[Kamal Mostafa]

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>
---
 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 8747f7c5e0e7..b4121784b4e8 100644
--- a/arch/arm64/include/asm/pci.h
+++ b/arch/arm64/include/asm/pci.h
@@ -23,6 +23,7 @@
  */
 #define PCI_DMA_BUS_IS_PHYS	(0)
 
+#define arch_can_pci_mmap_wc() 1
 #define ARCH_GENERIC_PCI_MMAP_RESOURCE	1
 
 extern int isa_dma_bridge_buggy;
-- 
2.17.1