diff options
| -rw-r--r-- | arch/arm/include/asm/pgtable.h | 2 | ||||
| -rw-r--r-- | arch/arm/include/asm/system.h | 2 | ||||
| -rw-r--r-- | arch/arm/mm/Kconfig | 19 |
3 files changed, 21 insertions, 2 deletions
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h index 11397687f42..ab68cf1ef80 100644 --- a/arch/arm/include/asm/pgtable.h +++ b/arch/arm/include/asm/pgtable.h @@ -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 diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h index ca88e6a8470..02f5d99adbc 100644 --- a/arch/arm/include/asm/system.h +++ b/arch/arm/include/asm/system.h @@ -137,7 +137,7 @@ extern unsigned int user_debug; #define dmb() __asm__ __volatile__ ("" : : : "memory") #endif -#if __LINUX_ARM_ARCH__ >= 7 || defined(CONFIG_SMP) +#if defined(CONFIG_ARM_DMA_MEM_BUFFERABLE) || defined(CONFIG_SMP) #define mb() dmb() #define rmb() dmb() #define wmb() dmb() diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index c4ed9f93f64..573528d9c6d 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -781,3 +781,22 @@ config ARM_L1_CACHE_SHIFT int default 6 if ARM_L1_CACHE_SHIFT_6 default 5 + +config ARM_DMA_MEM_BUFFERABLE + bool "Use non-cacheable memory for DMA" if CPU_V6 && !CPU_V7 + default y if CPU_V6 || CPU_V7 + help + Historically, the kernel has used strongly ordered mappings to + provide DMA coherent memory. With the advent of ARMv7, mapping + memory with differing types results in unpredictable behaviour, + so on these CPUs, this option is forced on. + + Multiple mappings with differing attributes is also unpredictable + on ARMv6 CPUs, but since they do not have aggressive speculative + prefetch, no harm appears to occur. + + However, drivers may be missing the necessary barriers for ARMv6, + and therefore turning this on may result in unpredictable driver + behaviour. Therefore, we offer this as an option. + + You are recommended say 'Y' here and debug any affected drivers. |