linux-kernel - [PATCH] arm64: Enable PCI write-combine resources under sysfs

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Message-ID: <20200821155154.umharcbew46hkhuq@amazon.com>
Date:   Fri, 21 Aug 2020 15:51:54 +0000
From:   Clint Sbisa <csbisa@...zon.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
CC:     Clint Sbisa <csbisa@...zon.com>,
        Benjamin Herrenschmidt <benh@...zon.com>,
        Ali Saidi <alisaidi@...zon.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        "Guy Tzalik" <gtzalik@...zon.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] arm64: Enable PCI write-combine resources under sysfs

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@...zon.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() \
 	(pci_has_flag(PCI_REASSIGN_ALL_BUS))
 
+#define arch_can_pci_mmap_wc() 1
 #define ARCH_GENERIC_PCI_MMAP_RESOURCE	1
 
 extern int isa_dma_bridge_buggy;
-- 
2.23.3