The dw_dmac driver was earlier adapted to do 64-bit transfers
on the memory side (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 to set a new slave property
max_mem_width to limit the size.
Allowable values for dw_dma_slave::max_mem_width are:
0 : leave it up to dw_dmac (64 bits)
1 : 16-bits
2 : 32-bits
Signed-off-by: Hein Tibosch <hein_tibo...@yahoo.es>
---
drivers/dma/dw_dmac.c | 8 ++++++++
include/linux/dw_dmac.h | 3 +++
2 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 7212961..a4bdf1d 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -754,6 +754,10 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct
scatterlist *sgl,
mem_width = 1;
else
mem_width = 0;
+ /* Some controllers don't support 64-bits mem access */
+ if (dws->max_mem_width &&
+ mem_width > dws->max_mem_width)
+ mem_width = dws->max_mem_width;
slave_sg_todev_fill_desc:
desc = dwc_desc_get(dwc);
@@ -821,6 +825,10 @@ slave_sg_todev_fill_desc:
mem_width = 1;
else
mem_width = 0;
+ /* Some controllers don't support 64-bits mem access */
+ if (dws->max_mem_width &&
+ mem_width > dws->max_mem_width)
+ mem_width = dws->max_mem_width;
slave_sg_fromdev_fill_desc:
desc = dwc_desc_get(dwc);
diff --git a/include/linux/dw_dmac.h b/include/linux/dw_dmac.h
index 2412e02..60b01c3 100644
--- a/include/linux/dw_dmac.h
+++ b/include/linux/dw_dmac.h
@@ -51,6 +51,8 @@ enum dw_dma_msize {
* @cfg_lo: Platform-specific initializer for the CFG_LO register
* @src_master: src master for transfers on allocated channel.
* @dst_master: dest master for transfers on allocated channel.
+ * @max_mem_width: max value for SRC/DST_TR_WIDTH register
+ * default 0 means: leave it up to driver
*/
struct dw_dma_slave {
struct device *dma_dev;
@@ -58,6 +60,7 @@ struct dw_dma_slave {
u32 cfg_lo;
u8 src_master;
u8 dst_master;
+ u8 max_mem_width;
};
/* Platform-configurable bits in CFG_HI */
--
1.7.8.0
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