arch/c6x: add option to skip sync on DMA map and unmap

This change allows us to pass DMA_ATTR_SKIP_CPU_SYNC which allows us to
avoid invoking cache line invalidation if the driver will just handle it
later via a sync_for_cpu or sync_for_device call.

Link: http://lkml.kernel.org/r/20161110113442.76501.7673.stgit@ahduyck-blue-test.jf.intel.com
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/c6x/kernel/dma.c b/arch/c6x/kernel/dma.c
index db4a6a301f5e..6752df32ef06 100644
--- a/arch/c6x/kernel/dma.c
+++ b/arch/c6x/kernel/dma.c
@@ -42,14 +42,17 @@ static dma_addr_t c6x_dma_map_page(struct device *dev, struct page *page,
 {
         dma_addr_t handle = virt_to_phys(page_address(page) + offset);
 
-        c6x_dma_sync(handle, size, dir);
+        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+                c6x_dma_sync(handle, size, dir);
+
         return handle;
 }
 
 static void c6x_dma_unmap_page(struct device *dev, dma_addr_t handle,
                 size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-        c6x_dma_sync(handle, size, dir);
+        if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+                c6x_dma_sync(handle, size, dir);
 }
 
 static int c6x_dma_map_sg(struct device *dev, struct scatterlist *sglist,
@@ -60,7 +63,8 @@ static int c6x_dma_map_sg(struct device *dev, struct scatterlist *sglist,
 
         for_each_sg(sglist, sg, nents, i) {
                 sg->dma_address = sg_phys(sg);
-                c6x_dma_sync(sg->dma_address, sg->length, dir);
+                if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+                        c6x_dma_sync(sg->dma_address, sg->length, dir);
         }
 
         return nents;
@@ -72,9 +76,11 @@ static void c6x_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
         struct scatterlist *sg;
         int i;
 
+        if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+                return;
+
         for_each_sg(sglist, sg, nents, i)
                 c6x_dma_sync(sg_dma_address(sg), sg->length, dir);
-
 }
 
 static void c6x_dma_sync_single_for_cpu(struct device *dev, dma_addr_t handle,