[PATCH v2 2/4] iio/adc: (max1363) Add support for external reference voltage

[Guenter Roeck]

Implement external reference voltage as regulator named "vref".

Signed-off-by: Guenter Roeck <linux at roeck-us.net>
---
v2: Use regulator API to specify vref instead of creating new devicetree
    bindings.
    Keep reference voltage internally in uV, as this is the scale provided
    by the regulator subsystem. We need the value in uV anyway, so that does
    make some sense.

 drivers/iio/adc/max1363.c |   52 +++++++++++++++++++++++++++++++++------------
 1 file changed, 39 insertions(+), 13 deletions(-)

diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
index 1353fda..cac73d7 100644
--- a/drivers/iio/adc/max1363.c
+++ b/drivers/iio/adc/max1363.c
@@ -163,6 +163,8 @@ struct max1363_chip_info {
  * @mask_low:		bitmask for enabled low thresholds
  * @thresh_high:	high threshold values
  * @thresh_low:		low threshold values
+ * @vref:		Reference voltage regulator
+ * @vref_uv:		Actual (external or internal) reference voltage
  */
 struct max1363_state {
 	struct i2c_client		*client;
@@ -182,6 +184,8 @@ struct max1363_state {
 	/* 4x unipolar first then the fours bipolar ones */
 	s16				thresh_high[8];
 	s16				thresh_low[8];
+	struct regulator		*vref;
+	u32				vref_uv;
 };
 
 #define MAX1363_MODE_SINGLE(_num, _mask) {				\
@@ -393,6 +397,8 @@ static int max1363_read_raw(struct iio_dev *indio_dev,
 {
 	struct max1363_state *st = iio_priv(indio_dev);
 	int ret;
+	unsigned long scale_uv;
+
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
 		ret = max1363_read_single_chan(indio_dev, chan, val, m);
@@ -400,16 +406,10 @@ static int max1363_read_raw(struct iio_dev *indio_dev,
 			return ret;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
-		if ((1 << (st->chip_info->bits + 1)) >
-		    st->chip_info->int_vref_mv) {
-			*val = 0;
-			*val2 = 500000;
-			return IIO_VAL_INT_PLUS_MICRO;
-		} else {
-			*val = (st->chip_info->int_vref_mv)
-				>> st->chip_info->bits;
-			return IIO_VAL_INT;
-		}
+		scale_uv = st->vref_uv >> st->chip_info->bits;
+		*val = scale_uv / 1000;
+		*val2 = (scale_uv % 1000) * 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
 	default:
 		return -EINVAL;
 	}
@@ -1390,12 +1390,16 @@ static const struct max1363_chip_info max1363_chip_info_tbl[] = {
 
 static int max1363_initial_setup(struct max1363_state *st)
 {
-	st->setupbyte = MAX1363_SETUP_AIN3_IS_AIN3_REF_IS_VDD
-		| MAX1363_SETUP_POWER_UP_INT_REF
-		| MAX1363_SETUP_INT_CLOCK
+	st->setupbyte = MAX1363_SETUP_INT_CLOCK
 		| MAX1363_SETUP_UNIPOLAR
 		| MAX1363_SETUP_NORESET;
 
+	if (st->vref)
+		st->setupbyte |= MAX1363_SETUP_AIN3_IS_REF_EXT_TO_REF;
+	else
+		st->setupbyte |= MAX1363_SETUP_POWER_UP_INT_REF
+		  | MAX1363_SETUP_AIN3_IS_AIN3_REF_IS_INT;
+
 	/* Set scan mode writes the config anyway so wait until then */
 	st->setupbyte = MAX1363_SETUP_BYTE(st->setupbyte);
 	st->current_mode = &max1363_mode_table[st->chip_info->default_mode];
@@ -1533,6 +1537,7 @@ static int max1363_probe(struct i2c_client *client,
 	int ret;
 	struct max1363_state *st;
 	struct iio_dev *indio_dev;
+	struct regulator *vref;
 
 	indio_dev = iio_device_alloc(sizeof(struct max1363_state));
 	if (indio_dev == NULL) {
@@ -1563,6 +1568,23 @@ static int max1363_probe(struct i2c_client *client,
 	st->chip_info = &max1363_chip_info_tbl[id->driver_data];
 	st->client = client;
 
+	st->vref_uv = st->chip_info->int_vref_mv * 1000;
+	vref = devm_regulator_get(&client->dev, "vref");
+	if (!IS_ERR(vref)) {
+		int vref_uv;
+
+		ret = regulator_enable(vref);
+		if (ret)
+			goto error_disable_reg;
+		st->vref = vref;
+		vref_uv = regulator_get_voltage(vref);
+		if (vref_uv <= 0) {
+			ret = -EINVAL;
+			goto error_disable_reg;
+		}
+		st->vref_uv = vref_uv;
+	}
+
 	ret = max1363_alloc_scan_masks(indio_dev);
 	if (ret)
 		goto error_disable_reg;
@@ -1604,6 +1626,8 @@ static int max1363_probe(struct i2c_client *client,
 error_uninit_buffer:
 	iio_triggered_buffer_cleanup(indio_dev);
 error_disable_reg:
+	if (st->vref)
+		regulator_disable(st->vref);
 	regulator_disable(st->reg);
 error_unregister_map:
 	iio_map_array_unregister(indio_dev);
@@ -1620,6 +1644,8 @@ static int max1363_remove(struct i2c_client *client)
 
 	iio_device_unregister(indio_dev);
 	iio_triggered_buffer_cleanup(indio_dev);
+	if (st->vref)
+		regulator_disable(st->vref);
 	regulator_disable(st->reg);
 	iio_map_array_unregister(indio_dev);
 	iio_device_free(indio_dev);
-- 
1.7.9.7