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| author | Catalin Marinas <catalin.marinas@arm.com> | 2010-06-21 16:10:07 +0200 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2010-07-01 11:12:31 +0200 |
| commit | ad642d9f58f1af6e96efccb5f84e52c6d01db5c4 (patch) | |
| tree | 4319ed1e81f50c7035457cc0fa1cf4bcdf760abb /arch/arm/mm | |
| parent | ARM: 6187/1: The v6_dma_inv_range() function must preserve data on SMP (diff) | |
| download | linux-ad642d9f58f1af6e96efccb5f84e52c6d01db5c4.tar.xz linux-ad642d9f58f1af6e96efccb5f84e52c6d01db5c4.zip | |
ARM: 6188/1: Add a config option for the ARM11MPCore DMA cache maintenance workaround
Commit f4d6477f introduced a workaround for the lack of hardware
broadcasting of the cache maintenance operations on ARM11MPCore.
However, the workaround is only valid on CPUs that do not do speculative
loads into the D-cache.
This patch adds a Kconfig option with the corresponding help to make the
above clear. When the DMA_CACHE_RWFO option is disabled, the kernel
behaviour is that prior to the f4d6477f commit. This also allows ARMv6
UP processors with speculative loads to work correctly.
For other processors, a different workaround may be needed.
Cc: Ronen Shitrit <rshitrit@marvell.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mm')
| -rw-r--r-- | arch/arm/mm/Kconfig | 19 | ||||
| -rw-r--r-- | arch/arm/mm/cache-v6.S | 15 |
2 files changed, 31 insertions, 3 deletions
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 346ae14824a5..fc1b2fa59429 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -735,6 +735,25 @@ config NEEDS_SYSCALL_FOR_CMPXCHG Forget about fast user space cmpxchg support. It is just not possible. +config DMA_CACHE_RWFO + bool "Enable read/write for ownership DMA cache maintenance" + depends on CPU_V6 && SMP + default y + help + The Snoop Control Unit on ARM11MPCore does not detect the + cache maintenance operations and the dma_{map,unmap}_area() + functions may leave stale cache entries on other CPUs. By + enabling this option, Read or Write For Ownership in the ARMv6 + DMA cache maintenance functions is performed. These LDR/STR + instructions change the cache line state to shared or modified + so that the cache operation has the desired effect. + + Note that the workaround is only valid on processors that do + not perform speculative loads into the D-cache. For such + processors, if cache maintenance operations are not broadcast + in hardware, other workarounds are needed (e.g. cache + maintenance broadcasting in software via FIQ). + config OUTER_CACHE bool diff --git a/arch/arm/mm/cache-v6.S b/arch/arm/mm/cache-v6.S index 332b48c6d4ff..86aa689ef1aa 100644 --- a/arch/arm/mm/cache-v6.S +++ b/arch/arm/mm/cache-v6.S @@ -211,7 +211,7 @@ v6_dma_inv_range: mcrne p15, 0, r1, c7, c15, 1 @ clean & invalidate unified line #endif 1: -#ifdef CONFIG_SMP +#ifdef CONFIG_DMA_CACHE_RWFO ldr r2, [r0] @ read for ownership str r2, [r0] @ write for ownership #endif @@ -235,7 +235,7 @@ v6_dma_inv_range: v6_dma_clean_range: bic r0, r0, #D_CACHE_LINE_SIZE - 1 1: -#ifdef CONFIG_SMP +#ifdef CONFIG_DMA_CACHE_RWFO ldr r2, [r0] @ read for ownership #endif #ifdef HARVARD_CACHE @@ -258,7 +258,7 @@ v6_dma_clean_range: ENTRY(v6_dma_flush_range) bic r0, r0, #D_CACHE_LINE_SIZE - 1 1: -#ifdef CONFIG_SMP +#ifdef CONFIG_DMA_CACHE_RWFO ldr r2, [r0] @ read for ownership str r2, [r0] @ write for ownership #endif @@ -284,9 +284,13 @@ ENTRY(v6_dma_map_area) add r1, r1, r0 teq r2, #DMA_FROM_DEVICE beq v6_dma_inv_range +#ifndef CONFIG_DMA_CACHE_RWFO + b v6_dma_clean_range +#else teq r2, #DMA_TO_DEVICE beq v6_dma_clean_range b v6_dma_flush_range +#endif ENDPROC(v6_dma_map_area) /* @@ -296,6 +300,11 @@ ENDPROC(v6_dma_map_area) * - dir - DMA direction */ ENTRY(v6_dma_unmap_area) +#ifndef CONFIG_DMA_CACHE_RWFO + add r1, r1, r0 + teq r2, #DMA_TO_DEVICE + bne v6_dma_inv_range +#endif mov pc, lr ENDPROC(v6_dma_unmap_area) |