Patch "dmaengine: bcm2835: Fix cyclic DMA period splitting" has been added to the 4.9-stable tree

Patch "dmaengine: bcm2835: Fix cyclic DMA period splitting" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    dmaengine: bcm2835: Fix cyclic DMA period splitting

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dmaengine-bcm2835-fix-cyclic-dma-period-splitting.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 2201ac6129fa162ac24da089a034bb0971648ebb Mon Sep 17 00:00:00 2001
From: Matthias Reichl <hias@horus.com>
Date: Mon, 20 Feb 2017 20:01:16 +0100
Subject: dmaengine: bcm2835: Fix cyclic DMA period splitting

From: Matthias Reichl <hias@horus.com>

commit 2201ac6129fa162ac24da089a034bb0971648ebb upstream.

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>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/dma/bcm2835-dma.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -251,8 +251,11 @@ static void bcm2835_dma_create_cb_set_le
 	 */
 
 	/* 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;


Patches currently in stable-queue which might be from hias@horus.com are

queue-4.9/dmaengine-bcm2835-fix-cyclic-dma-period-splitting.patch