ASoC: cs4270: allow passing freq=0 in set_dai_sysclk()

For setups with variable MCLKs, the current logic of limiting the
available sampling rates at startup time is not sufficient. We need to
be able to change the setting at a later point, and so the codec must
offer all possible rates until the hw_params are given.

This patches allows that by passing 0 as 'freq' argument to
cs4270_set_dai_sysclk().
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/cs4270.c

@@ -200,6 +200,11 @@ static struct cs4270_mode_ratios cs4270_mode_ratios[] = {
  * This function must be called by the machine driver's 'startup' function,
  * otherwise the list of supported sample rates will not be available in
  * time for ALSA.
+ *
+ * For setups with variable MCLKs, pass 0 as 'freq' argument. This will cause
+ * theoretically possible sample rates to be enabled. Call it again with a
+ * proper value set one the external clock is set (most probably you would do
+ * that from a machine's driver 'hw_param' hook.
  */
 static int cs4270_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 				 int clk_id, unsigned int freq, int dir)
@@ -213,20 +218,27 @@ static int cs4270_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 
 	cs4270->mclk = freq;
 
-	for (i = 0; i < NUM_MCLK_RATIOS; i++) {
-		unsigned int rate = freq / cs4270_mode_ratios[i].ratio;
-		rates |= snd_pcm_rate_to_rate_bit(rate);
-		if (rate < rate_min)
-			rate_min = rate;
-		if (rate > rate_max)
-			rate_max = rate;
-	}
-	/* FIXME: soc should support a rate list */
-	rates &= ~SNDRV_PCM_RATE_KNOT;
+	if (cs4270->mclk) {
+		for (i = 0; i < NUM_MCLK_RATIOS; i++) {
+			unsigned int rate = freq / cs4270_mode_ratios[i].ratio;
+			rates |= snd_pcm_rate_to_rate_bit(rate);
+			if (rate < rate_min)
+				rate_min = rate;
+			if (rate > rate_max)
+				rate_max = rate;
+		}
+		/* FIXME: soc should support a rate list */
+		rates &= ~SNDRV_PCM_RATE_KNOT;
 
-	if (!rates) {
-		dev_err(codec->dev, "could not find a valid sample rate\n");
-		return -EINVAL;
+		if (!rates) {
+			dev_err(codec->dev, "could not find a valid sample rate\n");
+			return -EINVAL;
+		}
+	} else {
+		/* enable all possible rates */
+		rates = SNDRV_PCM_RATE_8000_192000;
+		rate_min = 8000;
+		rate_max = 192000;
 	}
 
 	codec_dai->playback.rates = rates;