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ALSA: firewire-lib/dice/speakers: Add common PCM constraints for AMDTP streams 

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.

[Fixed the compile error due to the missing "&" by tiwai]

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Sakamoto 2014-04-25 22:44:52 +09:00 committed by Takashi Iwai
parent 10550bea44
commit 7b2d99fa6b
4 changed files with 61 additions and 23 deletions
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56
sound/firewire/amdtp.c
View File

@ -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"
@ -104,6 +105,61 @@ 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

3
sound/firewire/amdtp.h
View File

@ -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);

17
sound/firewire/dice.c
View File

@ -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;

8
sound/firewire/speakers.c
View File

@ -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);
if (err < 0)
return err;