ARM: 6111/1: Implement read/write for ownership in the ARMv6 DMA cache ops

The Snoop Control Unit on the ARM11MPCore hardware does not detect the
cache operations and the dma_cache_maint*() functions may leave stale
cache entries on other CPUs. The solution implemented in this patch
performs a Read or Write For Ownership in the ARMv6 DMA cache
maintenance functions. These LDR/STR instructions change the cache line
state to shared or exclusive so that the cache maintenance operation has
the desired effect.

Tested-by: George G. Davis <gdavis@mvista.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 13 insertions, 4 deletions

diff --git a/arch/arm/mm/cache-v6.S b/arch/arm/mm/cache-v6.S
index 9d89c67a1cc3..e46ecd847138 100644
--- a/arch/arm/mm/cache-v6.S
+++ b/arch/arm/mm/cache-v6.S
@@ -211,6 +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
+#endif
 #ifdef HARVARD_CACHE
         mcr     p15, 0, r0, c7, c6, 1           @ invalidate D line
 #else
@@ -231,6 +234,9 @@ v6_dma_inv_range:
 v6_dma_clean_range:
         bic     r0, r0, #D_CACHE_LINE_SIZE - 1
 1:
+#ifdef CONFIG_SMP
+        ldr     r2, [r0]                        @ read for ownership
+#endif
 #ifdef HARVARD_CACHE
         mcr     p15, 0, r0, c7, c10, 1          @ clean D line
 #else
@@ -251,6 +257,10 @@ v6_dma_clean_range:
 ENTRY(v6_dma_flush_range)
         bic     r0, r0, #D_CACHE_LINE_SIZE - 1
 1:
+#ifdef CONFIG_SMP
+        ldr     r2, [r0]                        @ read for ownership
+        str     r2, [r0]                        @ write for ownership
+#endif
 #ifdef HARVARD_CACHE
         mcr     p15, 0, r0, c7, c14, 1          @ clean & invalidate D line
 #else
@@ -273,7 +283,9 @@ ENTRY(v6_dma_map_area)
         add     r1, r1, r0
         teq     r2, #DMA_FROM_DEVICE
         beq     v6_dma_inv_range
-        b       v6_dma_clean_range
+        teq     r2, #DMA_TO_DEVICE
+        beq     v6_dma_clean_range
+        b       v6_dma_flush_range
 ENDPROC(v6_dma_map_area)
 
 /*
@@ -283,9 +295,6 @@ ENDPROC(v6_dma_map_area)
  *      - dir   - DMA direction
  */
 ENTRY(v6_dma_unmap_area)
-        add     r1, r1, r0
-        teq     r2, #DMA_TO_DEVICE
-        bne     v6_dma_inv_range
         mov     pc, lr
 ENDPROC(v6_dma_unmap_area)