1 From f0f4368b3497d129c0c4ca0565f5b6656faed474 Mon Sep 17 00:00:00 2001
2 From: Matthias Reichl <hias@horus.com>
3 Date: Sun, 11 Oct 2015 12:28:30 +0200
4 Subject: [PATCH] bcm2835-dma: Limit cyclic transfers on lite channels to 32k
6 Transfers larger than 32k cause repeated clicking with I2S soundcards.
7 The exact reason is yet unknown, so limit to 32k as bcm2708-dmaengine
8 did as an intermediate fix.
10 drivers/dma/bcm2835-dma.c | 8 +++++++-
11 1 file changed, 7 insertions(+), 1 deletion(-)
13 --- a/drivers/dma/bcm2835-dma.c
14 +++ b/drivers/dma/bcm2835-dma.c
15 @@ -144,6 +144,12 @@ struct bcm2835_desc {
17 #define MAX_LITE_TRANSFER (SZ_64K - 4)
20 + * Transfers larger than 32k cause issues with the bcm2708-i2s driver,
21 + * so limit transfer size to 32k as bcm2708-dmaengine did.
23 +#define MAX_CYCLIC_LITE_TRANSFER SZ_32K
25 static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
27 return container_of(d, struct bcm2835_dmadev, ddev);
28 @@ -412,7 +418,7 @@ static struct dma_async_tx_descriptor *b
31 if (c->ch >= 8) /* LITE channel */
32 - max_size = MAX_LITE_TRANSFER;
33 + max_size = MAX_CYCLIC_LITE_TRANSFER;
35 max_size = MAX_NORMAL_TRANSFER;
36 period_len = min(period_len, max_size);