Hi Robin

On 04/11/2018 05:14 PM, Robin Murphy wrote:

On 11/04/18 15:44, Pierre-Yves MORDRET wrote:

quoted

Both buffer Transfer Length (TLEN if any) and transfer size have to be
aligned on burst size (burst beats*bus width).

Signed-off-by: Pierre-Yves MORDRET <redacted>
---
   Version history:
     v1:
        * Initial
     v2:
---
---
  drivers/dma/stm32-mdma.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
index daa1602..fbcffa2 100644
--- a/drivers/dma/stm32-mdma.c
+++ b/drivers/dma/stm32-mdma.c

@@ -413,7 +413,7 @@ static u32 stm32_mdma_get_best_burst(u32 buf_len, u32 tlen, u32 max_burst,
  	u32 best_burst = max_burst;
  	u32 burst_len = best_burst * width;
  
-	while ((burst_len > 0) && (tlen % burst_len)) {
+	while ((burst_len > 0) && (((tlen | buf_len) & (burst_len - 1)) != 0)) {
  		best_burst = best_burst >> 1;
  		burst_len = best_burst * width;
  	}

FWIW, doesn't that whole loop come down to just:

	burst_len = min(ffs(tlen | buf_len), max_burst * width);

No sure it ends as expected. or I miss something or don't understand this statement
I tried with "relevant value" : i.e. best_burst = 32, Tlen=128(default) and
buf_len = 64, width= 4. This statements gets me something wrong output => 7
instead of 16 * 4.
I doubt :)

?

Robin.