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ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus

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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>
This commit is contained in:
Vladimir Murzin 2017-05-24 11:24:31 +01:00 committed by Christoph Hellwig
parent 1c51c429f3
commit 1b11d39e6a
1 changed files with 6 additions and 2 deletions
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8
arch/arm/mm/Kconfig
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@ -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