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authorAidan MacDonald <aidanmacdonald.0x0@gmail.com>2022-04-11 16:36:18 +0100
committerVinod Koul <vkoul@kernel.org>2022-04-20 17:13:22 +0530
commit2128565a8d3055623f651712b7faa3d66ce4f02c (patch)
treeb1f6f22d834ee8912dcab05b2addc6f6b6b0b0d8 /drivers/dma/dma-jz4780.c
parentd965068259d13fde49487b45064106d3d0c57a74 (diff)
dmaengine: jz4780: set DMA maximum segment size
Set the maximum segment size, since the hardware can do transfers larger than the default 64 KiB returned by dma_get_max_seg_size(). The maximum segment size is limited by the 24-bit transfer count field in DMA descriptors. The number of bytes is equal to the transfer count times the transfer size unit, which is selected by the driver based on the DMA buffer address and length of the transfer. The size unit can be as small as 1 byte, so set the maximum segment size to 2^24-1 bytes to ensure the transfer count will not overflow regardless of the size unit selected by the driver. Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com> Link: https://lore.kernel.org/r/20220411153618.49876-1-aidanmacdonald.0x0@gmail.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma/dma-jz4780.c')
-rw-r--r--drivers/dma/dma-jz4780.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index fc513eb2b289..e2ec540e6519 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -8,6 +8,7 @@
#include <linux/clk.h>
#include <linux/dmapool.h>
+#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
@@ -911,6 +912,14 @@ static int jz4780_dma_probe(struct platform_device *pdev)
dd = &jzdma->dma_device;
+ /*
+ * The real segment size limit is dependent on the size unit selected
+ * for the transfer. Because the size unit is selected automatically
+ * and may be as small as 1 byte, use a safe limit of 2^24-1 bytes to
+ * ensure the 24-bit transfer count in the descriptor cannot overflow.
+ */
+ dma_set_max_seg_size(dev, 0xffffff);
+
dma_cap_set(DMA_MEMCPY, dd->cap_mask);
dma_cap_set(DMA_SLAVE, dd->cap_mask);
dma_cap_set(DMA_CYCLIC, dd->cap_mask);