ALSA: firewire-lib: add PCM rules to obsolete PCM constraints based on LCM of SYT_INT...

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>

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index cb9acfe..fcd965f 100644 (file)
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -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;
 }