arch/m68k: add option to skip DMA sync as a part of mapping

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/20161110113457.76501.77603.stgit@ahduyck-blue-test.jf.intel.com
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index 8cf97cb..0707006 100644 (file)
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -134,7 +134,9 @@ static dma_addr_t m68k_dma_map_page(struct device *dev, struct page *page,
 {
        dma_addr_t handle = page_to_phys(page) + offset;
 
-       dma_sync_single_for_device(dev, handle, size, dir);
+       if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+               dma_sync_single_for_device(dev, handle, size, dir);
+
        return handle;
 }
 
@@ -146,6 +148,10 @@ static int m68k_dma_map_sg(struct device *dev, struct scatterlist *sglist,
 
        for_each_sg(sglist, sg, nents, i) {
                sg->dma_address = sg_phys(sg);
+
+               if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
+                       continue;
+
                dma_sync_single_for_device(dev, sg->dma_address, sg->length,
                                           dir);
        }