Commit 2201ac61 authored Feb 20, 2017 by Matthias Reichl Committed by Vinod Koul Mar 06, 2017

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>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

parent c1ae3cfa

drivers/dma/bcm2835-dma.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -251,8 +251,11 @@ 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;