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- From c9b92657b415bc1b855c394284efa0e33119ef61 Mon Sep 17 00:00:00 2001
- From: Matthias Reichl <hias@horus.com>
- Date: Sun, 11 Oct 2015 12:28:30 +0200
- Subject: [PATCH] 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);
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