3 files changed, 42 insertions, 13 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 e46ecd847138..86aa689ef1aa 100644
--- a/arch/arm/mm/cache-v6.S
+++ b/arch/arm/mm/cache-v6.S
@@ -211,8 +211,9 @@ v6_dma_inv_range:
         mcrne   p15, 0, r1, c7, c15, 1          @ clean & invalidate unified line
 #endif
 1:
-#ifdef CONFIG_SMP
-        str     r0, [r0]                        @ write for ownership
+#ifdef CONFIG_DMA_CACHE_RWFO
+        ldr     r2, [r0]                        @ read for ownership
+        str     r2, [r0]                        @ write for ownership
 #endif
 #ifdef HARVARD_CACHE
         mcr     p15, 0, r0, c7, c6, 1           @ invalidate D line
@@ -234,7 +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
@@ -257,7 +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
@@ -283,9 +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)
 
 /*
@@ -295,6 +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)
 
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 13fa536d82e6..9e7742f0a102 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -24,15 +24,6 @@
 #include <asm/tlbflush.h>
 #include <asm/sizes.h>
 
-/* Sanity check size */
-#if (CONSISTENT_DMA_SIZE % SZ_2M)
-#error "CONSISTENT_DMA_SIZE must be multiple of 2MiB"
-#endif
-
-#define CONSISTENT_OFFSET(x)    (((unsigned long)(x) - CONSISTENT_BASE) >> PAGE_SHIFT)
-#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - CONSISTENT_BASE) >> PGDIR_SHIFT)
-#define NUM_CONSISTENT_PTES (CONSISTENT_DMA_SIZE >> PGDIR_SHIFT)
-
 static u64 get_coherent_dma_mask(struct device *dev)
 {
         u64 mask = ISA_DMA_THRESHOLD;
@@ -123,6 +114,15 @@ static void __dma_free_buffer(struct page *page, size_t size)
 }
 
 #ifdef CONFIG_MMU
+/* Sanity check size */
+#if (CONSISTENT_DMA_SIZE % SZ_2M)
+#error "CONSISTENT_DMA_SIZE must be multiple of 2MiB"
+#endif
+
+#define CONSISTENT_OFFSET(x)    (((unsigned long)(x) - CONSISTENT_BASE) >> PAGE_SHIFT)
+#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - CONSISTENT_BASE) >> PGDIR_SHIFT)
+#define NUM_CONSISTENT_PTES (CONSISTENT_DMA_SIZE >> PGDIR_SHIFT)
+
 /*
  * These are the page tables (2MB each) covering uncached, DMA consistent allocations
  */