ASoC: dmic: add regulator support

Merge series from Olivier Moysan <olivier.moysan@foss.st.com>:

Digital microphones may be supplied by a regulator. Add regulator
support in dmic codec, to allow power management of the regulator
through the ASoC DAPM widgets.

Author: broonie

Documentation/devicetree/bindings/sound/dmic-codec.yaml

@@ -19,6 +19,9 @@ properties:
   '#sound-dai-cells':
     const: 0
 
+  vref-supply:
+    description: Phandle to the digital microphone reference supply
+
   dmicen-gpios:
     description: GPIO specifier for DMIC to control start and stop
     maxItems: 1

sound/soc/codecs/dmic.c

@@ -9,6 +9,7 @@
 #include <linux/gpio.h>
 #include <linux/gpio/consumer.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <sound/core.h>
@@ -25,6 +26,7 @@ module_param(wakeup_delay, uint, 0644);
 
 struct dmic {
 	struct gpio_desc *gpio_en;
+	struct regulator *vref;
 	int wakeup_delay;
 	/* Delay after DMIC mode switch */
 	int modeswitch_delay;
@@ -55,22 +57,33 @@ static int dmic_aif_event(struct snd_soc_dapm_widget *w,
 			  struct snd_kcontrol *kcontrol, int event) {
 	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
 	struct dmic *dmic = snd_soc_component_get_drvdata(component);
+	int ret = 0;
 
 	switch (event) {
 	case SND_SOC_DAPM_POST_PMU:
 		if (dmic->gpio_en)
 			gpiod_set_value_cansleep(dmic->gpio_en, 1);
 
+		if (dmic->vref) {
+			ret = regulator_enable(dmic->vref);
+			if (ret)
+				return ret;
+		}
+
 		if (dmic->wakeup_delay)
 			msleep(dmic->wakeup_delay);
 		break;
 	case SND_SOC_DAPM_POST_PMD:
 		if (dmic->gpio_en)
 			gpiod_set_value_cansleep(dmic->gpio_en, 0);
+
+		if (dmic->vref)
+			ret = regulator_disable(dmic->vref);
+
 		break;
 	}
 
-	return 0;
+	return ret;
 }
 
 static struct snd_soc_dai_driver dmic_dai = {
@@ -100,6 +113,10 @@ static int dmic_component_probe(struct snd_soc_component *component)
 	if (!dmic)
 		return -ENOMEM;
 
+	dmic->vref = devm_regulator_get_optional(component->dev, "vref");
+	if (IS_ERR(dmic->vref) && PTR_ERR(dmic->vref) != -ENODEV)
+		return dev_err_probe(component->dev, PTR_ERR(dmic->vref), "Failed to get vref\n");
+
 	dmic->gpio_en = devm_gpiod_get_optional(component->dev,
 						"dmicen", GPIOD_OUT_LOW);
 	if (IS_ERR(dmic->gpio_en))