2016-12-02 10:50:26 +00:00
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From c9b92657b415bc1b855c394284efa0e33119ef61 Mon Sep 17 00:00:00 2001
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2016-01-17 10:42:23 +00:00
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From: Matthias Reichl <hias@horus.com>
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Date: Sun, 11 Oct 2015 12:28:30 +0200
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2016-09-10 12:54:26 +00:00
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Subject: [PATCH] bcm2835-dma: Limit cyclic transfers on lite channels to 32k
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2016-01-17 10:42:23 +00:00
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Transfers larger than 32k cause repeated clicking with I2S soundcards.
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The exact reason is yet unknown, so limit to 32k as bcm2708-dmaengine
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did as an intermediate fix.
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---
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drivers/dma/bcm2835-dma.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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--- a/drivers/dma/bcm2835-dma.c
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+++ b/drivers/dma/bcm2835-dma.c
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@@ -144,6 +144,12 @@ struct bcm2835_desc {
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*/
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#define MAX_LITE_TRANSFER (SZ_64K - 4)
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+/*
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+ * Transfers larger than 32k cause issues with the bcm2708-i2s driver,
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+ * so limit transfer size to 32k as bcm2708-dmaengine did.
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+ */
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+#define MAX_CYCLIC_LITE_TRANSFER SZ_32K
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+
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static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
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{
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return container_of(d, struct bcm2835_dmadev, ddev);
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@@ -412,7 +418,7 @@ static struct dma_async_tx_descriptor *b
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d->c = c;
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d->dir = direction;
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if (c->ch >= 8) /* LITE channel */
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- max_size = MAX_LITE_TRANSFER;
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+ max_size = MAX_CYCLIC_LITE_TRANSFER;
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else
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max_size = MAX_NORMAL_TRANSFER;
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period_len = min(period_len, max_size);
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