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Commit 7b2d99fa authored by Takashi Sakamoto's avatar Takashi Sakamoto Committed by Takashi Iwai
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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: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 10550bea

sound/firewire/amdtp.c

+56 −0
Original line number Diff line number Diff line
@@ -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

sound/firewire/amdtp.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

sound/firewire/dice.c

+1 −16
Original line number Diff line number Diff line
@@ -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;

sound/firewire/speakers.c

+1 −7
Original line number Diff line number Diff line
@@ -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;