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authorVladimir Murzin <vladimir.murzin@arm.com>2017-05-24 11:24:31 +0100
committerChristoph Hellwig <hch@lst.de>2017-06-30 10:03:10 -0700
commit1b11d39e6a6864a9dfb64e2c3ac03090e3b34399 (patch)
tree0cc05ea30843b0a613eb1e1b2d7a6078c88e815c
parent1c51c429f30ea10428337f3a33c12059ba59f668 (diff)
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ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus
Now, we have dedicated non-cacheable region for consistent DMA operations. However, that region can still be marked as bufferable by MPU, so it'd be safer to have barriers by default. M-class machines that didn't need it until now also likely won't need it in the future, therefore, we offer this as an option. Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org> Tested-by: Andras Szemzo <sza@esh.hu> Tested-by: Alexandre TORGUE <alexandre.torgue@st.com> Reviewed-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> Acked-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: Christoph Hellwig <hch@lst.de>
-rw-r--r--arch/arm/mm/Kconfig8
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index c6c4c9c8824b..877a0e3fd17d 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1045,8 +1045,8 @@ config ARM_L1_CACHE_SHIFT
default 5
config ARM_DMA_MEM_BUFFERABLE
- bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
- default y if CPU_V6 || CPU_V6K || CPU_V7
+ bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K || CPU_V7M) && !CPU_V7
+ default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
help
Historically, the kernel has used strongly ordered mappings to
provide DMA coherent memory. With the advent of ARMv7, mapping
@@ -1061,6 +1061,10 @@ config ARM_DMA_MEM_BUFFERABLE
and therefore turning this on may result in unpredictable driver
behaviour. Therefore, we offer this as an option.
+ On some of the beefier ARMv7-M machines (with DMA and write
+ buffers) you likely want this enabled, while those that
+ didn't need it until now also won't need it in the future.
+
You are recommended say 'Y' here and debug any affected drivers.
config ARM_HEAVY_MB
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