diff mbox

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

Message ID 1526366456-20470-2-git-send-email-sriramx.periyasamy@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Sriram Periyasamy May 15, 2018, 6:40 a.m. UTC 
From: Pardha Saradhi K <pardha.saradhi.kesapragada@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@intel.com>
Signed-off-by: Sriram Periyasamy <sriramx.periyasamy@intel.com>
---
 sound/hda/hdac_stream.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Comments

Takashi Iwai May 15, 2018, 7:34 a.m. UTC | #1 
On Tue, 15 May 2018 08:40:53 +0200,
Sriram Periyasamy wrote:
> 
> From: Pardha Saradhi K <pardha.saradhi.kesapragada@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.

This is already done in snd_hdac_stream_sync().

Doing this in snd_hdac_stream_clear() may delay the sync'ed operations
unnecessarily.


thanks,

Takashi

> 
> Signed-off-by: Pardha Saradhi K <pardha.saradhi.kesapragada@intel.com>
> Signed-off-by: Sriram Periyasamy <sriramx.periyasamy@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
>
diff mbox

Patch

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;
 }