[alsa-devel] [PATCH 1/3] ASoC: es8316: judge PCM rate at later timing

[Katsuhiro Suzuki]

This patch change the judge timing about playing/capturing PCM rate.

Original code set constraints list of PCM rate limits at set_sysclk.
This strategy works well if system is using fixed rate clock.

But some boards and SoC (such as RockPro64 and RockChip I2S) has
connected SoC MCLK out to ES8316 MCLK in. In this case, SoC side I2S
will choose suitable frequency of MCLK such as fs * mclk-fs when
user starts playing or capturing.

Bad scenario as follows (mclk-fs = 256):
  - Initialize sysclk by correct value (Ex. 12.288MHz)
    - ES8316 set constraints of PCM rate by sysclk
      48kHz (1/256), 32kHz (1/384), 30.720kHz (1/400),
      24kHz (1/512), 16kHz (1/768), 12kHz (1/1024)
  - Play 48kHz sound, it's acceptable
  - Sysclk is not changed

  - Play 32kHz sound, it's acceptable
  - Set sysclk by 8.192MHz (= fs * mclk-fs = 32k * 256)
    - ES8316 set constraints of PCM rate by sysclk
      32kHz (1/256), 21.33kHz (1/384), 20.48kHz (1/400),
      16kHz (1/512), 10.66kHz (1/768), 8kHz (1/1024)

  - Play 48kHz again, but it's NOT acceptable because constraints
    list does not allow 48kHz

Root cause of this strange behavior is changing constraints list at
set_sysclk timing. It seems that is too early to determine. So this
patch does not use constraints list and check PCM rate limit more
later timing at hw_params.

Signed-off-by: Katsuhiro Suzuki <katsuhiro at katsuster.net>
---
 sound/soc/codecs/es8316.c | 37 +++++++++++++++----------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/sound/soc/codecs/es8316.c b/sound/soc/codecs/es8316.c
index ed2959dbe1fb..229808fa627c 100644
--- a/sound/soc/codecs/es8316.c
+++ b/sound/soc/codecs/es8316.c
@@ -363,27 +363,12 @@ static int es8316_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 {
 	struct snd_soc_component *component = codec_dai->component;
 	struct es8316_priv *es8316 = snd_soc_component_get_drvdata(component);
-	int i;
-	int count = 0;
 
 	es8316->sysclk = freq;
 
 	if (freq == 0)
 		return 0;
 
-	/* Limit supported sample rates to ones that can be autodetected
-	 * by the codec running in slave mode.
-	 */
-	for (i = 0; i < NR_SUPPORTED_MCLK_LRCK_RATIOS; i++) {
-		const unsigned int ratio = supported_mclk_lrck_ratios[i];
-
-		if (freq % ratio == 0)
-			es8316->allowed_rates[count++] = freq / ratio;
-	}
-
-	es8316->sysclk_constraints.list = es8316->allowed_rates;
-	es8316->sysclk_constraints.count = count;
-
 	return 0;
 }
 
@@ -449,13 +434,6 @@ static int es8316_pcm_startup(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
-	/* The set of sample rates that can be supported depends on the
-	 * MCLK supplied to the CODEC.
-	 */
-	snd_pcm_hw_constraint_list(substream->runtime, 0,
-				   SNDRV_PCM_HW_PARAM_RATE,
-				   &es8316->sysclk_constraints);
-
 	return 0;
 }
 
@@ -466,12 +444,27 @@ static int es8316_pcm_hw_params(struct snd_pcm_substream *substream,
 	struct snd_soc_component *component = dai->component;
 	struct es8316_priv *es8316 = snd_soc_component_get_drvdata(component);
 	u8 wordlen = 0;
+	int i;
 
 	if (!es8316->sysclk) {
 		dev_err(component->dev, "No MCLK configured\n");
 		return -EINVAL;
 	}
 
+	/* Limit supported sample rates to ones that can be autodetected
+	 * by the codec running in slave mode.
+	 */
+	for (i = 0; i < NR_SUPPORTED_MCLK_LRCK_RATIOS; i++) {
+		const unsigned int ratio = supported_mclk_lrck_ratios[i];
+
+		if (es8316->sysclk % ratio != 0)
+			continue;
+		if (es8316->sysclk / ratio == params_rate(params))
+			break;
+	}
+	if (i == NR_SUPPORTED_MCLK_LRCK_RATIOS)
+		return -EINVAL;
+
 	switch (params_format(params)) {
 	case SNDRV_PCM_FORMAT_S16_LE:
 		wordlen = ES8316_SERDATA2_LEN_16;
-- 
2.23.0.rc1