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From c2dd47a309d6eee486191ef7805ba3f544ff3dae Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Thu, 21 Apr 2016 15:44:14 +0100
Subject: [PATCH 299/423] bcm2835-i2s: Reduce the TX DREQ threshold
TX FIFO overrun is thought to be the cause of channel swapping, so
reducing the DREQ threshold seems reasonable and appears to be
effective.
See: https://github.com/raspberrypi/linux/issues/1417
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
sound/soc/bcm/bcm2835-i2s.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
--- a/sound/soc/bcm/bcm2835-i2s.c
+++ b/sound/soc/bcm/bcm2835-i2s.c
@@ -555,15 +555,22 @@ static int bcm2835_i2s_hw_params(struct
/* Setup the DMA parameters */
regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
- BCM2835_I2S_RXTHR(1)
- | BCM2835_I2S_TXTHR(1)
- | BCM2835_I2S_DMAEN, 0xffffffff);
+ BCM2835_I2S_RXTHR(3)
+ | BCM2835_I2S_TXTHR(3)
+ | BCM2835_I2S_DMAEN,
+ BCM2835_I2S_RXTHR(1)
+ | BCM2835_I2S_TXTHR(1)
+ | BCM2835_I2S_DMAEN);
regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_DREQ_A_REG,
- BCM2835_I2S_TX_PANIC(0x10)
- | BCM2835_I2S_RX_PANIC(0x30)
- | BCM2835_I2S_TX(0x30)
- | BCM2835_I2S_RX(0x20), 0xffffffff);
+ BCM2835_I2S_TX_PANIC(0x7f)
+ | BCM2835_I2S_RX_PANIC(0x7f)
+ | BCM2835_I2S_TX(0x7f)
+ | BCM2835_I2S_RX(0x7f),
+ BCM2835_I2S_TX_PANIC(0x10)
+ | BCM2835_I2S_RX_PANIC(0x30)
+ | BCM2835_I2S_TX(0x20)
+ | BCM2835_I2S_RX(0x20));
/* Clear FIFOs */
bcm2835_i2s_clear_fifos(dev, true, true);
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