openwrtv4/target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-cyclic-DMA-period-splitting.patch
Álvaro Fernández Rojas 20402106a3 brcm2708: update linux 4.4 patches to latest version
As usual these patches were extracted and rebased from the raspberry pi repo:
https://github.com/raspberrypi/linux/tree/rpi-4.4.y

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
2016-07-09 16:29:18 +02:00

38 lines
1.4 KiB
Diff

From 74d0d3161d711b51be692cf1750b6eb60719f782 Mon Sep 17 00:00:00 2001
From: Matthias Reichl <hias@horus.com>
Date: Tue, 7 Jun 2016 19:37:10 +0200
Subject: [PATCH 406/423] 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>
---
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
@@ -252,8 +252,11 @@ 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;