ARM: dma-mapping: introduce the idea of buffer ownership

The DMA API has the notion of buffer ownership; make it explicit in the
ARM implementation of this API.  This gives us a set of hooks to allow
us to deal with CPU cache issues arising from non-cache coherent DMA.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-By: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-By: Jamie Iles <jamie@jamieiles.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 26325cb5d368..a316c9459526 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -573,8 +573,12 @@ void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
         int i;
 
         for_each_sg(sg, s, nents, i) {
-                dmabounce_sync_for_cpu(dev, sg_dma_address(s), 0,
-                                        sg_dma_len(s), dir);
+                if (!dmabounce_sync_for_cpu(dev, sg_dma_address(s), 0,
+                                            sg_dma_len(s), dir))
+                        continue;
+
+                __dma_page_dev_to_cpu(sg_page(s), s->offset,
+                                      s->length, dir);
         }
 }
 EXPORT_SYMBOL(dma_sync_sg_for_cpu);
@@ -597,9 +601,8 @@ void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
                                         sg_dma_len(s), dir))
                         continue;
 
-                if (!arch_is_coherent())
-                        dma_cache_maint_page(sg_page(s), s->offset,
-                                             s->length, dir);
+                __dma_page_cpu_to_dev(sg_page(s), s->offset,
+                                      s->length, dir);
         }
 }
 EXPORT_SYMBOL(dma_sync_sg_for_device);