ASoC: da7218: Improve driver efficiency with regards to MCLK usage

Currently MCLK remains enabled during bias STANDBY state, and this
is not necessary. This patch updates the code to handle enabling
and disabling of MCLK, if provided, when moving between STANDBY
and PREPARE states, therefore saving power when no active streams
present.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/da7218.c

@@ -2583,20 +2583,22 @@ static int da7218_set_bias_level(struct snd_soc_codec *codec,
 
 	switch (level) {
 	case SND_SOC_BIAS_ON:
-	case SND_SOC_BIAS_PREPARE:
 		break;
-	case SND_SOC_BIAS_STANDBY:
-		if (snd_soc_codec_get_bias_level(codec) == SND_SOC_BIAS_OFF) {
-			/* MCLK */
+	case SND_SOC_BIAS_PREPARE:
+		/* Enable MCLK for transition to ON state */
+		if (snd_soc_codec_get_bias_level(codec) == SND_SOC_BIAS_STANDBY) {
 			if (da7218->mclk) {
 				ret = clk_prepare_enable(da7218->mclk);
 				if (ret) {
-					dev_err(codec->dev,
-						"Failed to enable mclk\n");
+					dev_err(codec->dev, "Failed to enable mclk\n");
 					return ret;
 				}
 			}
+		}
 
+		break;
+	case SND_SOC_BIAS_STANDBY:
+		if (snd_soc_codec_get_bias_level(codec) == SND_SOC_BIAS_OFF) {
 			/* Master bias */
 			snd_soc_update_bits(codec, DA7218_REFERENCES,
 					    DA7218_BIAS_EN_MASK,
@@ -2606,6 +2608,10 @@ static int da7218_set_bias_level(struct snd_soc_codec *codec,
 			snd_soc_update_bits(codec, DA7218_LDO_CTRL,
 					    DA7218_LDO_EN_MASK,
 					    DA7218_LDO_EN_MASK);
+		} else {
+			/* Remove MCLK */
+			if (da7218->mclk)
+				clk_disable_unprepare(da7218->mclk);
 		}
 		break;
 	case SND_SOC_BIAS_OFF:
@@ -2619,10 +2625,6 @@ static int da7218_set_bias_level(struct snd_soc_codec *codec,
 			snd_soc_update_bits(codec, DA7218_REFERENCES,
 					    DA7218_BIAS_EN_MASK, 0);
 		}
-
-		/* MCLK */
-		if (da7218->mclk)
-			clk_disable_unprepare(da7218->mclk);
 		break;
 	}