openwrt/target/linux/brcm2708/patches-4.4/0024-bcm2835-dma-Limit-cyclic-transfers-on-lite-channels-.patch
Felix Fietkau 4224b52c3a brcm2708: add linux 4.4 support
- random-bcm2708 and spi-bcm2708 have been removed.
- sound-soc-bcm2708-i2s has been upstreamed as sound-soc-bcm2835-i2s.

Let's keep linux 4.1 for a while, since linux 4.4 appears to have some issues
with multicast traffic on RPi ethernet:
https://gist.github.com/Noltari/5b1cfdecce5ed4bc08fd

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

SVN-Revision: 48266
2016-01-17 10:42:23 +00:00

38 lines
1.2 KiB
Diff

From c7e464c38d38ad59899c94dfad6c3455c18f7d76 Mon Sep 17 00:00:00 2001
From: Matthias Reichl <hias@horus.com>
Date: Sun, 11 Oct 2015 12:28:30 +0200
Subject: [PATCH 024/127] bcm2835-dma: Limit cyclic transfers on lite channels
to 32k
Transfers larger than 32k cause repeated clicking with I2S soundcards.
The exact reason is yet unknown, so limit to 32k as bcm2708-dmaengine
did as an intermediate fix.
---
drivers/dma/bcm2835-dma.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -144,6 +144,12 @@ struct bcm2835_desc {
*/
#define MAX_LITE_TRANSFER (SZ_64K - 4)
+/*
+ * Transfers larger than 32k cause issues with the bcm2708-i2s driver,
+ * so limit transfer size to 32k as bcm2708-dmaengine did.
+ */
+#define MAX_CYCLIC_LITE_TRANSFER SZ_32K
+
static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
{
return container_of(d, struct bcm2835_dmadev, ddev);
@@ -412,7 +418,7 @@ static struct dma_async_tx_descriptor *b
d->c = c;
d->dir = direction;
if (c->ch >= 8) /* LITE channel */
- max_size = MAX_LITE_TRANSFER;
+ max_size = MAX_CYCLIC_LITE_TRANSFER;
else
max_size = MAX_NORMAL_TRANSFER;
period_len = min(period_len, max_size);