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Commit 59502295 authored by Takashi Sakamoto's avatar Takashi Sakamoto Committed by Takashi Iwai
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ALSA: firewire-lib: add PCM rules to obsolete PCM constraints based on LCM of SYT_INTERVAL 



In blocking mode of IEC 61883-1/6, when one isochronous packet includes
data for events, the data is for the same number of events as
SYT_INTERVAL decided according to sampling transmission frequency (SFC).

IEC 61883-1/6 engine of ALSA firewire stack applies constraints of
period and buffer size of PCM intermediate buffer of PCM substream.
At present, this constraint is designed to round the size up/down to
32 frames. This value comes from the least common multiple (LCM) of
SYT_INTERVAL. Although this looks to work well, in lower sampling
rate, applications are not allowed to set size of period quite near
period time constraint (at present 5 msec per period).

This commit adds PCM rules for period/buffer size and rate to obsoletes
the constraints based on LCM.

Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 96395e86

sound/firewire/amdtp-stream.c

+71 −7
Original line number Diff line number Diff line
@@ -140,6 +140,59 @@ const unsigned int amdtp_rate_table[CIP_SFC_COUNT] = { 
};

EXPORT_SYMBOL(amdtp_rate_table);



static int apply_constraint_to_size(struct snd_pcm_hw_params *params,

				    struct snd_pcm_hw_rule *rule)

{

	struct snd_interval *s = hw_param_interval(params, rule->var);

	const struct snd_interval *r =

		hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);

	struct snd_interval t = {

		.min = s->min, .max = s->max, .integer = 1,

	};

	int i;



	for (i = 0; i < CIP_SFC_COUNT; ++i) {

		unsigned int rate = amdtp_rate_table[i];

		unsigned int step = amdtp_syt_intervals[i];



		if (!snd_interval_test(r, rate))

			continue;



		t.min = roundup(t.min, step);

		t.max = rounddown(t.max, step);

	}



	if (snd_interval_checkempty(&t))

		return -EINVAL;



	return snd_interval_refine(s, &t);

}



static int apply_constraint_to_rate(struct snd_pcm_hw_params *params,

				    struct snd_pcm_hw_rule *rule)

{

	struct snd_interval *r =

			hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);

	const struct snd_interval *s = hw_param_interval_c(params, rule->deps[0]);

	struct snd_interval t = {

		.min = UINT_MAX, .max = 0, .integer = 1,

	};

	int i;



	for (i = 0; i < CIP_SFC_COUNT; ++i) {

		unsigned int step = amdtp_syt_intervals[i];

		unsigned int rate = amdtp_rate_table[i];



		if (s->min % step || s->max % step)

			continue;



		t.min = min(t.min, rate);

		t.max = max(t.max, rate);

	}



	return snd_interval_refine(r, &t);

}



/**

 * amdtp_stream_add_pcm_hw_constraints - add hw constraints for PCM substream

 * @s:		the AMDTP stream, which must be initialized.
@@ -194,16 +247,27 @@ int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s, 
	 * 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 align period/buffer sizes to current SYT_INTERVAL.

	 *

	 * TODO: These constraints can be improved with proper rules.

	 * Currently apply LCM of SYT_INTERVALs.

	 */

	err = snd_pcm_hw_constraint_step(runtime, 0,

					 SNDRV_PCM_HW_PARAM_PERIOD_SIZE, 32);

	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_SIZE,

				  apply_constraint_to_size, NULL,

				  SNDRV_PCM_HW_PARAM_RATE, -1);

	if (err < 0)

		goto end;

	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,

				  apply_constraint_to_rate, NULL,

				  SNDRV_PCM_HW_PARAM_PERIOD_SIZE, -1);

	if (err < 0)

		goto end;

	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_SIZE,

				  apply_constraint_to_size, NULL,

				  SNDRV_PCM_HW_PARAM_RATE, -1);

	if (err < 0)

		goto end;

	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,

				  apply_constraint_to_rate, NULL,

				  SNDRV_PCM_HW_PARAM_BUFFER_SIZE, -1);

	if (err < 0)

		goto end;

	err = snd_pcm_hw_constraint_step(runtime, 0,

					 SNDRV_PCM_HW_PARAM_BUFFER_SIZE, 32);

end:

	return err;

}