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authorVladimir Murzin <vladimir.murzin@arm.com>2017-05-24 11:24:30 +0100
committerChristoph Hellwig <hch@lst.de>2017-06-30 10:03:09 -0700
commit1c51c429f30ea10428337f3a33c12059ba59f668 (patch)
tree0f0b3526eb11716d25230ab653d8d050a7d504b6 /arch/arm/Kconfig
parent07c75d7a6b9eae24ab72c6eb2fbd39963775b0bf (diff)
downloadlinux-1c51c429f30ea10428337f3a33c12059ba59f668.tar.bz2
ARM: NOMMU: Introduce dma operations for noMMU
R/M classes of cpus can have memory covered by MPU which in turn might configure RAM as Normal i.e. bufferable and cacheable. It breaks dma_alloc_coherent() and friends, since data can stuck in caches now or be buffered. This patch factors out DMA support for NOMMU configuration into separate entity which provides dedicated dma_ops. We have to handle there several cases: - configurations with MMU/MPU setup - configurations without MMU/MPU setup - special case for M-class, since caches and MPU there are optional In general we rely on default DMA area for coherent allocations or/and per-device memory reserves suitable for coherent DMA, so if such regions are set coherent allocations go from there. In case MMU/MPU was not setup we fallback to normal page allocator for DMA memory allocation. In case we run M-class cpus, for configuration without cache support (like Cortex-M3/M4) dma operations are forced to be coherent and wired with dma-noop (such decision is made based on cacheid global variable); however, if caches are detected there and no DMA coherent region is given (either default or per-device), dma is disallowed even MPU is not set - it is because M-class implement system memory map which defines part of address space as Normal memory. Reported-by: Alexandre Torgue <alexandre.torgue@st.com> Reported-by: Andras Szemzo <sza@esh.hu> 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: Arnd Bergmann <arnd@arndb.de> Acked-by: Russell King <rmk+kernel@armlinux.org.uk> [hch: removed the dma_supported() implementation that isn't required anymore] Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'arch/arm/Kconfig')
-rw-r--r--arch/arm/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c1a35f15838..8a94f2c7606c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -22,6 +22,7 @@ config ARM
select CLONE_BACKWARDS
select CPU_PM if (SUSPEND || CPU_IDLE)
select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
+ select DMA_NOOP_OPS if !MMU
select EDAC_SUPPORT
select EDAC_ATOMIC_SCRUB
select GENERIC_ALLOCATOR