From fc5bc111e65b27883284591aec9db5a290665ac9 Mon Sep 17 00:00:00 2001 From: Matthias Reichl 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);