[alsa-devel] [PATCH 1/4] ALSA: hda: Make sure DMA is stopped by reading back the RUN bit

[Sriram Periyasamy]

From: Pardha Saradhi K <pardha.saradhi.kesapragada at intel.com>

As per HW recommendation, after clearing the RUN bit,
software must read a 0 from the RUN bit, before modifying
related control registers or re-starting the DMA engine.

Signed-off-by: Pardha Saradhi K <pardha.saradhi.kesapragada at intel.com>
Signed-off-by: Sriram Periyasamy <sriramx.periyasamy at intel.com>
---
 sound/hda/hdac_stream.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
index e1472c7ab6c1..2000ea6f48fa 100644
--- a/sound/hda/hdac_stream.c
+++ b/sound/hda/hdac_stream.c
@@ -70,8 +70,23 @@ EXPORT_SYMBOL_GPL(snd_hdac_stream_start);
  */
 void snd_hdac_stream_clear(struct hdac_stream *azx_dev)
 {
+	int timeout = 300;
+	unsigned char val;
+
 	snd_hdac_stream_updateb(azx_dev, SD_CTL,
 				SD_CTL_DMA_START | SD_INT_MASK, 0);
+
+	do {
+		udelay(3);
+		val = snd_hdac_stream_readb(azx_dev, SD_CTL) &
+				SD_CTL_DMA_START;
+		if (!val)
+			break;
+	} while (--timeout);
+
+	if (!timeout)
+		dev_err(azx_dev->bus->dev, "unable to stop the stream\n");
+
 	snd_hdac_stream_writeb(azx_dev, SD_STS, SD_INT_MASK); /* to be sure */
 	azx_dev->running = false;
 }
-- 
2.7.4