On 2017年01月11日 08:57, Shawn Guo wrote:
On Tue, Jan 10, 2017 at 05:23:40PM +0800, Jun Nie wrote:
Fix build warning that related to PAGE_SIZE. The maximum DMA
length has nothing to do with PAGE_SIZE, just use a fix number
for the definition.
drivers/dma/zx_dma.c: In function 'zx_dma_prep_memcpy':
drivers/dma/zx_dma.c:523:8: warning: division by zero [-Wdiv-by-zero]
drivers/dma/zx_dma.c: In function 'zx_dma_prep_slave_sg':
drivers/dma/zx_dma.c:567:11: warning: division by zero [-Wdiv-by-zero]
Signed-off-by: Jun Nie <jun.nie@xxxxxxxxxx>
HDMI audio works fine with the change, so:
Tested-by: Shawn Guo <shawn.guo@xxxxxxxxxx>
But out of curiosity ...
---
drivers/dma/zx_dma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/zx_dma.c b/drivers/dma/zx_dma.c
index 42ff3e6..2bb6953 100644
--- a/drivers/dma/zx_dma.c
+++ b/drivers/dma/zx_dma.c
@@ -26,7 +26,7 @@
#define DRIVER_NAME "zx-dma"
#define DMA_ALIGN 4
-#define DMA_MAX_SIZE (0x10000 - PAGE_SIZE)
+#define DMA_MAX_SIZE (0x10000 - 512)
Why do we need to minus some amount of bytes from 64KiB size for
DMA_MAX_SIZE at all?
For better alignment of DMA transfer size. Maximum size 0xFFFF minus 32
or 64 shall be OK, but I prefer to 512 for better performance and safe.
#define LLI_BLOCK_SIZE (4 * PAGE_SIZE)
Why do we need to have LLI_BLOCK_SIZE vary with PAGE_SIZE?
It is a trade off for dmam_pool size. 4 pages size does introduce
pressure to memory management and allocation, and size is enough for
most of DMA descriptor usage.
Shawn
#define REG_ZX_SRC_ADDR 0x00
--
1.9.1
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