linux-kernel - [PATCH 1/1] ASoC: dwc: fix dma stop transferring issue

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Date:	Mon, 28 Sep 2015 14:36:16 +0800
From:	"yitian" <yitian.bu@...gramtek.com>
To:	<lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
	<tiwai@...e.com>, <Andrew.Jackson@....com>, <wsa@...-dreams.de>
Cc:	<alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH 1/1] ASoC: dwc: fix dma stop transferring issue

Designware I2S uses tx empty and rx available signals as the DMA
handshaking signals. during music playing, if XRUN occurs,
i2s_stop() function will be executed and both tx and rx irq are
masked, when music contintes to be played, i2s_start() is executed
but both tx and rx irq are not unmasked which cause I2S stop
sending DMA handshaking signal to DMA controller, and it finally
cause music playing will be stopped once XRUN occurs for the first
time.

Signed-off-by: Yitian Bu <yitian.bu@...gramtek.com>
---
 sound/soc/dwc/designware_i2s.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/sound/soc/dwc/designware_i2s.c b/sound/soc/dwc/designware_i2s.c
index a3e97b4..4d3e1d3 100644
--- a/sound/soc/dwc/designware_i2s.c
+++ b/sound/soc/dwc/designware_i2s.c
@@ -144,10 +144,19 @@ static void i2s_start(struct dw_i2s_dev *dev,
 
 	i2s_write_reg(dev->i2s_base, IER, 1);
 
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		for (i = 0; i < 4; i++) {
+			irq = i2s_read_reg(dev->i2s_base, IMR(i));
+			i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x30);
+		}
 		i2s_write_reg(dev->i2s_base, ITER, 1);
-	else
+	} else {
+		for (i = 0; i < 4; i++) {
+			irq = i2s_read_reg(dev->i2s_base, IMR(i));
+			i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x03);
+		}
 		i2s_write_reg(dev->i2s_base, IRER, 1);
+	}
 
 	i2s_write_reg(dev->i2s_base, CER, 1);
 }
-- 
1.7.12.4

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