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

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  [RESEND PATCH] dmaengine: bcm2835: Fix cyclic DMA period splitting Matthias Reichl <hias@horus.com> - 2017-02-20 20:10 +0100
    Re: [RESEND PATCH] dmaengine: bcm2835: Fix cyclic DMA period  splitting Vinod Koul <vinod.koul@intel.com> - 2017-02-22 03:50 +0100

#1584828 — [RESEND PATCH] dmaengine: bcm2835: Fix cyclic DMA period splitting

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(-)

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;
-- 
2.1.4

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#1585890 — Re: [RESEND PATCH] dmaengine: bcm2835: Fix cyclic DMA period splitting

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

-- 
~Vinod

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