async_xor: dma_map destination DMA_BIDIRECTIONAL
Mapping the destination multiple times is a misuse of the dma-api.
Since the destination may be reused as a source, ensure that it is only
mapped once and that it is mapped bidirectionally. This appears to add
ugliness on the unmap side in that it always reads back the destination
address from the descriptor, but gcc can determine that dma_unmap is a
nop and not emit the code that calculates its arguments.
Cc: <stable@kernel.org>
Cc: Saeed Bishara <saeed@marvell.com>
Acked-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/dma/mv_xor.c b/drivers/dma/mv_xor.c
index 0328da0..bcda174 100644
--- a/drivers/dma/mv_xor.c
+++ b/drivers/dma/mv_xor.c
@@ -311,17 +311,26 @@
enum dma_ctrl_flags flags = desc->async_tx.flags;
u32 src_cnt;
dma_addr_t addr;
+ dma_addr_t dest;
+ src_cnt = unmap->unmap_src_cnt;
+ dest = mv_desc_get_dest_addr(unmap);
if (!(flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
- addr = mv_desc_get_dest_addr(unmap);
- dma_unmap_page(dev, addr, len, DMA_FROM_DEVICE);
+ enum dma_data_direction dir;
+
+ if (src_cnt > 1) /* is xor ? */
+ dir = DMA_BIDIRECTIONAL;
+ else
+ dir = DMA_FROM_DEVICE;
+ dma_unmap_page(dev, dest, len, dir);
}
if (!(flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
- src_cnt = unmap->unmap_src_cnt;
while (src_cnt--) {
addr = mv_desc_get_src_addr(unmap,
src_cnt);
+ if (addr == dest)
+ continue;
dma_unmap_page(dev, addr, len,
DMA_TO_DEVICE);
}