Re: [PATCH 2/3] ALSA: hda: Add behaviour flag for dma stop delay

[Takashi Iwai <tiwai@suse.de>]

On Wed, 05 Aug 2020 11:11:15 +0200,
Mohan Kumar wrote:
> 
> Behaviour flag dma_stop_delay is added as a new member in hdac_bus
> structure to avoid memory decode error incase DMA RUN bit is not
> disabled in the given timeout from snd_hdac_stream_sync function and
> followed by stream reset which results in memory decode error between
> reset set and clear operation.

The new field looks like not only a flag but also contains the actual
delay time in usec.  Please give a short comment at the struct field.


thanks,

Takashi

> 
> Signed-off-by: Mohan Kumar <mkumard@nvidia.com>
> ---
>  include/sound/hdaudio.h | 2 ++
>  sound/hda/hdac_stream.c | 7 +++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
> index c1f78d9a6e47..cf77c6b83016 100644
> --- a/include/sound/hdaudio.h
> +++ b/include/sound/hdaudio.h
> @@ -347,6 +347,8 @@ struct hdac_bus {
>  
>  	int bdl_pos_adj;		/* BDL position adjustment */
>  
> +	unsigned int dma_stop_delay;
> +
>  	/* locks */
>  	spinlock_t reg_lock;
>  	struct mutex cmd_mutex;
> diff --git a/sound/hda/hdac_stream.c b/sound/hda/hdac_stream.c
> index a38a2af1654f..abe7a1b16fe1 100644
> --- a/sound/hda/hdac_stream.c
> +++ b/sound/hda/hdac_stream.c
> @@ -150,9 +150,12 @@ void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
>  {
>  	unsigned char val;
>  	int timeout;
> +	int dma_run_state;
>  
>  	snd_hdac_stream_clear(azx_dev);
>  
> +	dma_run_state = snd_hdac_stream_readb(azx_dev, SD_CTL) & SD_CTL_DMA_START;
> +
>  	snd_hdac_stream_updateb(azx_dev, SD_CTL, 0, SD_CTL_STREAM_RESET);
>  	udelay(3);
>  	timeout = 300;
> @@ -162,6 +165,10 @@ void snd_hdac_stream_reset(struct hdac_stream *azx_dev)
>  		if (val)
>  			break;
>  	} while (--timeout);
> +
> +	if (azx_dev->bus->dma_stop_delay && dma_run_state)
> +		udelay(azx_dev->bus->dma_stop_delay);
> +
>  	val &= ~SD_CTL_STREAM_RESET;
>  	snd_hdac_stream_writeb(azx_dev, SD_CTL, val);
>  	udelay(3);
> -- 
> 2.17.1
>