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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: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Sakamoto 2018-10-01 04:11:49 +09:00 committed by Takashi Iwai
parent 96395e86e3
commit 5950229582
1 changed files with 71 additions and 7 deletions
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78
sound/firewire/amdtp-stream.c
View File

@ -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;
}