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ARM: Optionally allow ARMv6 to use 'normal, bufferable' memory for DMA

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Provide a configuration option to allow the ARMv6 to use normal
bufferable memory for coherent DMA.  This option is forced to 'y'
for ARMv7, and offered as a configuration option on ARMv6.

Enabling this option requires drivers to have the necessary barriers
to ensure that data in DMA coherent memory is visible prior to the
DMA operation commencing.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King
2010-05-15 11:02:43 +01:00
parent 8c0b742ca7
commit 47ab0dee66
3 changed files with 21 additions and 2 deletions
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2
arch/arm/include/asm/pgtable.h
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@@ -314,7 +314,7 @@ static inline pte_t pte_mkspecial(pte_t pte) { return pte; }
__pgprot_modify(prot, L_PTE_MT_MASK, L_PTE_MT_UNCACHED)
#define pgprot_writecombine(prot) \
__pgprot_modify(prot, L_PTE_MT_MASK, L_PTE_MT_BUFFERABLE)
#if __LINUX_ARM_ARCH__ >= 7
#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
#define pgprot_dmacoherent(prot) \
__pgprot_modify(prot, L_PTE_MT_MASK|L_PTE_EXEC, L_PTE_MT_BUFFERABLE)
#else