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bcm2835-i2s: Reduce the TX DREQ threshold

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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>
This commit is contained in:
Phil Elwell
2016-04-21 15:44:14 +01:00
committed by popcornmix
parent c6e9367e26
commit 622a56dbcb
1 changed files with 14 additions and 7 deletions
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13
sound/soc/bcm/bcm2835-i2s.c
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@@ -555,15 +555,22 @@ static int bcm2835_i2s_hw_params(struct snd_pcm_substream *substream,
/* Setup the DMA parameters */
regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_CS_A_REG,
BCM2835_I2S_RXTHR(3)
| BCM2835_I2S_TXTHR(3)
| BCM2835_I2S_DMAEN,
BCM2835_I2S_RXTHR(1)
| BCM2835_I2S_TXTHR(1)
| BCM2835_I2S_DMAEN, 0xffffffff);
| BCM2835_I2S_DMAEN);
regmap_update_bits(dev->i2s_regmap, BCM2835_I2S_DREQ_A_REG,
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(0x30)
| BCM2835_I2S_RX(0x20), 0xffffffff);
| BCM2835_I2S_TX(0x20)
| BCM2835_I2S_RX(0x20));
/* Clear FIFOs */
bcm2835_i2s_clear_fifos(dev, true, true);