[alsa-devel] [PATCH 11/49] firewire-lib/dice/speakers: Add common PCM constraints for AMDTP streams

[Takashi Iwai]

At Fri, 25 Apr 2014 22:44:52 +0900,
Takashi Sakamoto wrote:
> 
> This commit adds common PCM constraints according to current firewire-lib
> implementation.
> 
> 1.Maximum width for each sample is limited by 24.
> AM824 in IEC 61883-6 can deliver 24bit data.
> 
> 2. Minimum time for period is 5msec.
> Apply the old value. For shorter latency, further works are needed.
> 
> 3. In blocking mode, frames per period/buffer is aligned to 32.
> Each packet can include some frames depending on its sampling rate. In
> blocking mode, the number equals to SYT_INTERVAL. Currently firewire-lib
> can schedule snd_pcm_period_elapsed() for each packet. So, for accurate
> PCM interrupt, the number of frames per period/buffer should be aligned
> to SYT_INTERVAL.
> Currently firewire-lib is lack of better rules to achieve this. So LCM of
> each value of SYT_INTERVALs (=32) is applied. This can be improved for
> further work.
> 
> Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
> ---
>  sound/firewire/amdtp.c    | 56 +++++++++++++++++++++++++++++++++++++++++++++++
>  sound/firewire/amdtp.h    |  3 +++
>  sound/firewire/dice.c     | 17 +-------------
>  sound/firewire/speakers.c |  8 +------
>  4 files changed, 61 insertions(+), 23 deletions(-)
> 
> diff --git a/sound/firewire/amdtp.c b/sound/firewire/amdtp.c
> index 3475b76..ac8c358 100644
> --- a/sound/firewire/amdtp.c
> +++ b/sound/firewire/amdtp.c
> @@ -13,6 +13,7 @@
>  #include <linux/slab.h>
>  #include <linux/sched.h>
>  #include <sound/pcm.h>
> +#include <sound/pcm_params.h>
>  #include <sound/rawmidi.h>
>  #include "amdtp.h"
>  
> @@ -105,6 +106,61 @@ const unsigned int amdtp_syt_intervals[CIP_SFC_COUNT] = {
>  EXPORT_SYMBOL(amdtp_syt_intervals);
>  
>  /**
> + * amdtp_stream_add_pcm_hw_constraints - add hw constraints for PCM substream
> + * @s:		the AMDTP stream, which must be initialized.
> + * @runtime:	the PCM substream runtime
> + */
> +int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s,
> +					struct snd_pcm_runtime *runtime)
> +{
> +	int err;
> +
> +	/* AM824 in IEC 61883-6 can deliver 24bit data */
> +	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
> +	if (err < 0)
> +		goto end;
> +
> +	/*
> +	 * Currently firewire-lib processes 16 packets in one software
> +	 * interrupt callback. This equals to 2msec but actually the
> +	 * interval of the interrupts has a jitter.
> +	 * Additionally, even if adding a constraint to fit period size to
> +	 * 2msec, actual calculated frames per period doesn't equal to 2msec,
> +	 * depending on sampling rate.
> +	 * Anyway, the interval to call snd_pcm_period_elapsed() cannot 2msec.
> +	 * Here let us use 5msec for safe period interrupt.
> +	 */
> +	err = snd_pcm_hw_constraint_minmax(runtime,
> +					   SNDRV_PCM_HW_PARAM_PERIOD_TIME,
> +					   5000, UINT_MAX);
> +	if (err < 0)
> +		goto end;
> +
> +	/* Non-Blocking stream has no more constraints */
> +	if (!(s->flags & CIP_BLOCKING))
> +		goto end;
> +
> +	/*
> +	 * One AMDTP packet can include some frames. In blocking mode, the
> +	 * number equals to SYT_INTERVAL. So the number is 8, 16 or 32,
> +	 * depending on its sampling rate. For accurate period interrupt, it's
> +	 * preferrable to aligh period/buffer sizes to current SYT_INTERVAL.
> +	 *
> +	 * TODO: These constraints can be improved with propper rules.
> +	 * Currently apply LCM of SYT_INTEVALs.
> +	 */
> +	err = snd_pcm_hw_constraint_step(runtime, 0,
> +					 SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 32);
> +	if (err < 0)
> +		goto end;
> +	err = snd_pcm_hw_constraint_step(runtime, 0,
> +					 SNDRV_PCM_HW_PARAM_BUFFER_SIZE, 32);
> +end:
> +	return err;
> +}
> +EXPORT_SYMBOL(amdtp_stream_add_pcm_hw_constraints);
> +
> +/**
>   * amdtp_stream_set_parameters - set stream parameters
>   * @s: the AMDTP stream to configure
>   * @rate: the sample rate
> diff --git a/sound/firewire/amdtp.h b/sound/firewire/amdtp.h
> index db60425..d6bb7eb 100644
> --- a/sound/firewire/amdtp.h
> +++ b/sound/firewire/amdtp.h
> @@ -64,6 +64,7 @@ enum cip_sfc {
>  struct fw_unit;
>  struct fw_iso_context;
>  struct snd_pcm_substream;
> +struct snd_pcm_runtime;
>  struct snd_rawmidi_substream;
>  
>  enum amdtp_stream_direction {
> @@ -130,6 +131,8 @@ int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed);
>  void amdtp_stream_update(struct amdtp_stream *s);
>  void amdtp_stream_stop(struct amdtp_stream *s);
>  
> +int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s,
> +					struct snd_pcm_runtime *runtime);
>  void amdtp_stream_set_pcm_format(struct amdtp_stream *s,
>  				 snd_pcm_format_t format);
>  void amdtp_stream_pcm_prepare(struct amdtp_stream *s);
> diff --git a/sound/firewire/dice.c b/sound/firewire/dice.c
> index cd4c6b6..a9a30c0 100644
> --- a/sound/firewire/dice.c
> +++ b/sound/firewire/dice.c
> @@ -420,22 +420,7 @@ static int dice_open(struct snd_pcm_substream *substream)
>  	if (err < 0)
>  		goto err_lock;
>  
> -	err = snd_pcm_hw_constraint_step(runtime, 0,
> -					 SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 32);
> -	if (err < 0)
> -		goto err_lock;
> -	err = snd_pcm_hw_constraint_step(runtime, 0,
> -					 SNDRV_PCM_HW_PARAM_BUFFER_SIZE, 32);
> -	if (err < 0)
> -		goto err_lock;
> -
> -	err = snd_pcm_hw_constraint_minmax(runtime,
> -					   SNDRV_PCM_HW_PARAM_PERIOD_TIME,
> -					   5000, UINT_MAX);
> -	if (err < 0)
> -		goto err_lock;
> -
> -	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
> +	err = amdtp_stream_add_pcm_hw_constraints(&dice->stream, runtime);
>  	if (err < 0)
>  		goto err_lock;
>  
> diff --git a/sound/firewire/speakers.c b/sound/firewire/speakers.c
> index c07e7cd..3427527 100644
> --- a/sound/firewire/speakers.c
> +++ b/sound/firewire/speakers.c
> @@ -167,13 +167,7 @@ static int fwspk_open(struct snd_pcm_substream *substream)
>  	if (err < 0)
>  		return err;
>  
> -	err = snd_pcm_hw_constraint_minmax(runtime,
> -					   SNDRV_PCM_HW_PARAM_PERIOD_TIME,
> -					   5000, UINT_MAX);
> -	if (err < 0)
> -		return err;
> -
> -	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
> +	err = amdtp_stream_add_pcm_hw_constraints(fwspk->stream, runtime);

"&" is missing here.  I applied the patch with the fix.


Takashi