From 1b11d39e6a6864a9dfb64e2c3ac03090e3b34399 Mon Sep 17 00:00:00 2001 From: Vladimir Murzin Date: Wed, 24 May 2017 11:24:31 +0100 Subject: 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 Tested-by: Andras Szemzo Tested-by: Alexandre TORGUE Reviewed-by: Robin Murphy Signed-off-by: Vladimir Murzin Acked-by: Russell King Signed-off-by: Christoph Hellwig --- arch/arm/mm/Kconfig | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'arch/arm/mm') 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 -- cgit