power: supply: axp20x_usb_power: use IIO channels when available

The X-Powers AXP20X PMIC exposes the current current and voltage
measures via an internal ADC.

This adds the possibility to read IIO channels directly for processed
values rather than reading the registers and computing the value.

For backward compatibility purpose, if the IIO driver is not compiled,
this driver will fall back on previous behaviour which is direct
register readings.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/supply/axp20x_usb_power.c

@@ -22,6 +22,7 @@
 #include <linux/power_supply.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/iio/consumer.h>
 
 #define DRVNAME "axp20x-usb-power-supply"
 
@@ -49,6 +50,8 @@ struct axp20x_usb_power {
 	struct regmap *regmap;
 	struct power_supply *supply;
 	enum axp20x_variants axp20x_id;
+	struct iio_channel *vbus_v;
+	struct iio_channel *vbus_i;
 };
 
 static irqreturn_t axp20x_usb_power_irq(int irq, void *devid)
@@ -76,6 +79,20 @@ static int axp20x_usb_power_get_property(struct power_supply *psy,
 		val->intval = AXP20X_VBUS_VHOLD_uV(v);
 		return 0;
 	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		if (IS_ENABLED(CONFIG_AXP20X_ADC)) {
+			ret = iio_read_channel_processed(power->vbus_v,
+							 &val->intval);
+			if (ret)
+				return ret;
+
+			/*
+			 * IIO framework gives mV but Power Supply framework
+			 * gives uV.
+			 */
+			val->intval *= 1000;
+			return 0;
+		}
+
 		ret = axp20x_read_variable_width(power->regmap,
 						 AXP20X_VBUS_V_ADC_H, 12);
 		if (ret < 0)
@@ -107,6 +124,20 @@ static int axp20x_usb_power_get_property(struct power_supply *psy,
 		}
 		return 0;
 	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		if (IS_ENABLED(CONFIG_AXP20X_ADC)) {
+			ret = iio_read_channel_processed(power->vbus_i,
+							 &val->intval);
+			if (ret)
+				return ret;
+
+			/*
+			 * IIO framework gives mA but Power Supply framework
+			 * gives uA.
+			 */
+			val->intval *= 1000;
+			return 0;
+		}
+
 		ret = axp20x_read_variable_width(power->regmap,
 						 AXP20X_VBUS_I_ADC_H, 12);
 		if (ret < 0)
@@ -269,6 +300,36 @@ static const struct power_supply_desc axp22x_usb_power_desc = {
 	.set_property = axp20x_usb_power_set_property,
 };
 
+static int configure_iio_channels(struct platform_device *pdev,
+				  struct axp20x_usb_power *power)
+{
+	power->vbus_v = devm_iio_channel_get(&pdev->dev, "vbus_v");
+	if (IS_ERR(power->vbus_v)) {
+		if (PTR_ERR(power->vbus_v) == -ENODEV)
+			return -EPROBE_DEFER;
+		return PTR_ERR(power->vbus_v);
+	}
+
+	power->vbus_i = devm_iio_channel_get(&pdev->dev, "vbus_i");
+	if (IS_ERR(power->vbus_i)) {
+		if (PTR_ERR(power->vbus_i) == -ENODEV)
+			return -EPROBE_DEFER;
+		return PTR_ERR(power->vbus_i);
+	}
+
+	return 0;
+}
+
+static int configure_adc_registers(struct axp20x_usb_power *power)
+{
+	/* Enable vbus voltage and current measurement */
+	return regmap_update_bits(power->regmap, AXP20X_ADC_EN1,
+				  AXP20X_ADC_EN1_VBUS_CURR |
+				  AXP20X_ADC_EN1_VBUS_VOLT,
+				  AXP20X_ADC_EN1_VBUS_CURR |
+				  AXP20X_ADC_EN1_VBUS_VOLT);
+}
+
 static int axp20x_usb_power_probe(struct platform_device *pdev)
 {
 	struct axp20x_dev *axp20x = dev_get_drvdata(pdev->dev.parent);
@@ -308,10 +369,11 @@ static int axp20x_usb_power_probe(struct platform_device *pdev)
 		if (ret)
 			return ret;
 
-		/* Enable vbus voltage and current measurement */
+		if (IS_ENABLED(CONFIG_AXP20X_ADC))
-		ret = regmap_update_bits(power->regmap, AXP20X_ADC_EN1,
+			ret = configure_iio_channels(pdev, power);
-			AXP20X_ADC_EN1_VBUS_CURR | AXP20X_ADC_EN1_VBUS_VOLT,
+		else
-			AXP20X_ADC_EN1_VBUS_CURR | AXP20X_ADC_EN1_VBUS_VOLT);
+			ret = configure_adc_registers(power);
+
 		if (ret)
 			return ret;