[ARM] dma: don't touch cache on dma_*_for_cpu()

As per the dma_unmap_* calls, we don't touch the cache when a DMA
buffer transitions from device to CPU ownership.  Presently, no
problems have been identified with speculative cache prefetching
which in itself is a new feature in later architectures.  We may
have to revisit the DMA API later for these architectures anyway.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 3 insertions, 11 deletions

diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index 2544a087c213..ad62020763f1 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -376,11 +376,7 @@ static inline void dma_sync_single_range_for_cpu(struct device *dev,
 {
         BUG_ON(!valid_dma_direction(dir));
 
-        if (!dmabounce_sync_for_cpu(dev, handle, offset, size, dir))
-                return;
-
-        if (!arch_is_coherent())
-                dma_cache_maint(dma_to_virt(dev, handle) + offset, size, dir);
+        dmabounce_sync_for_cpu(dev, handle, offset, size, dir);
 }
 
 static inline void dma_sync_single_range_for_device(struct device *dev,
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 0e28cf33f7dd..67960017dc8f 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -585,12 +585,8 @@ void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
         int i;
 
         for_each_sg(sg, s, nents, i) {
-                if (!dmabounce_sync_for_cpu(dev, sg_dma_address(s), 0,
-                                        sg_dma_len(s), dir))
-                        continue;
-
-                if (!arch_is_coherent())
-                        dma_cache_maint(sg_virt(s), s->length, dir);
+                dmabounce_sync_for_cpu(dev, sg_dma_address(s), 0,
+                                        sg_dma_len(s), dir);
         }
 }
 EXPORT_SYMBOL(dma_sync_sg_for_cpu);