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[RESEND] dmaengine: bcm2835: Fix cyclic DMA period splitting

Message ID 20170220190115.GB4170@camel2.lan (mailing list archive)
State Accepted
Headers show

Commit Message

Matthias Reichl Feb. 20, 2017, 7:01 p.m. UTC 
The code responsible for splitting periods into chunks that
can be handled by the DMA controller missed to update total_len,
the number of bytes processed in the current period, when there
are more chunks to follow.

Therefore total_len was stuck at 0 and the code didn't work at all.
This resulted in a wrong control block layout and audio issues because
the cyclic DMA callback wasn't executing on period boundaries.

Fix this by adding the missing total_len update.

Signed-off-by: Matthias Reichl <hias@horus.com>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Tested-by: Clive Messer <clive.messer@digitaldreamtime.co.uk>
Reviewed-by: Eric Anholt <eric@anholt.net>
---
 drivers/dma/bcm2835-dma.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Vinod Koul Feb. 22, 2017, 2:41 a.m. UTC | #1 
On Mon, Feb 20, 2017 at 08:01:16PM +0100, Matthias Reichl wrote:
> The code responsible for splitting periods into chunks that
> can be handled by the DMA controller missed to update total_len,
> the number of bytes processed in the current period, when there
> are more chunks to follow.
> 
> Therefore total_len was stuck at 0 and the code didn't work at all.
> This resulted in a wrong control block layout and audio issues because
> the cyclic DMA callback wasn't executing on period boundaries.
> 
> Fix this by adding the missing total_len update.

Applied, thanks
diff mbox

Patch

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 80d35f7..599c218 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -253,8 +253,11 @@  static void bcm2835_dma_create_cb_set_length(
 	 */
 
 	/* have we filled in period_length yet? */
-	if (*total_len + control_block->length < period_len)
+	if (*total_len + control_block->length < period_len) {
+		/* update number of bytes in this period so far */
+		*total_len += control_block->length;
 		return;
+	}
 
 	/* calculate the length that remains to reach period_length */
 	control_block->length = period_len - *total_len;