brcm2708: add linux 4.4 support

[openwrt.git] / target / linux / brcm2708 / patches-4.4 / 0024-bcm2835-dma-Limit-cyclic-transfers-on-lite-channels-.patch

diff --git a/target/linux/brcm2708/patches-4.4/0024-bcm2835-dma-Limit-cyclic-transfers-on-lite-channels-.patch b/target/linux/brcm2708/patches-4.4/0024-bcm2835-dma-Limit-cyclic-transfers-on-lite-channels-.patch
new file mode 100644 (file)
index 0000000..4461fec
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.4/0024-bcm2835-dma-Limit-cyclic-transfers-on-lite-channels-.patch
@@ -0,0 +1,37 @@
+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);