[PATCH v3 2/3] dw_dmac: max_mem_width limits value for SRC/DST_TR_WID register

[Hein Tibosch <hein_tibosch@yahoo.es>]

The dw_dmac driver was earlier adapted to do 64-bit transfers on the memory
side (see https://lkml.org/lkml/2012/1/18/52)
This works on ARM platforms but for AVR32 (AP700x) the maximum allowed transfer
size is 32-bits.
This patch allows the arch code to set a new slave property max_mem_width to
limit the size.

Allowable values are:

#define	DW_MEM_WIDTH_64		0	/* default */
#define	DW_MEM_WIDTH_32		1	/* e.g. for avr32 */

Signed-off-by: Hein Tibosch <hein_tibosch@yahoo.es>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/dma/dw_dmac.c   |   10 +++++++---
 include/linux/dw_dmac.h |    3 +++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 7212961..11f8542 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -618,6 +618,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 		size_t len, unsigned long flags)
 {
 	struct dw_dma_chan	*dwc = to_dw_dma_chan(chan);
+	struct dw_dma_slave	*dws = chan->private;
 	struct dw_desc		*desc;
 	struct dw_desc		*first;
 	struct dw_desc		*prev;
@@ -639,7 +640,8 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 	 * We can be a lot more clever here, but this should take care
 	 * of the most common optimization.
 	 */
-	if (!((src | dest  | len) & 7))
+	if (dws->max_mem_width == DW_MEM_WIDTH_64 &&
+		!((src | dest  | len) & 7))
 		src_width = dst_width = 3;
 	else if (!((src | dest  | len) & 3))
 		src_width = dst_width = 2;
@@ -746,7 +748,8 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			if (!((mem | len) & 7))
+			if (dws->max_mem_width == DW_MEM_WIDTH_64 &&
+				!((mem | len) & 7))
 				mem_width = 3;
 			else if (!((mem | len) & 3))
 				mem_width = 2;
@@ -813,7 +816,8 @@ slave_sg_todev_fill_desc:
 			mem = sg_dma_address(sg);
 			len = sg_dma_len(sg);
 
-			if (!((mem | len) & 7))
+			if (dws->max_mem_width == DW_MEM_WIDTH_64 &&
+				!((mem | len) & 7))
 				mem_width = 3;
 			else if (!((mem | len) & 3))
 				mem_width = 2;
diff --git a/include/linux/dw_dmac.h b/include/linux/dw_dmac.h
index 2412e02..330afb2 100644
--- a/include/linux/dw_dmac.h
+++ b/include/linux/dw_dmac.h
@@ -58,6 +58,9 @@ struct dw_dma_slave {
 	u32			cfg_lo;
 	u8			src_master;
 	u8			dst_master;
+#define	DW_MEM_WIDTH_64		0
+#define	DW_MEM_WIDTH_32		1	/* e.g. for avr32 */
+	u8			max_mem_width;
 };
 
 /* Platform-configurable bits in CFG_HI */
-- 
1.7.8.0