ARM: 6188/1: Add a config option for the ARM11MPCore DMA cache maintenance workaround

[net-next-2.6.git] / arch / arm / mm / Kconfig

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 346ae14824a5ea96365f6e9b66fa8f78cd8cd4bc..fc1b2fa594293b5f8946229fd0db62db0ef67283 100644 (file)
--- 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