[RFC 11/11] iio/adc: (max1363) Add basic OF bindings and external vref support

[Guenter Roeck]

Signed-off-by: Guenter Roeck <linux at roeck-us.net>
---
 Documentation/devicetree/bindings/iio/max1363.txt |   54 +++++++++++++++++++++
 drivers/iio/adc/max1363.c                         |   54 ++++++++++++++++-----
 2 files changed, 95 insertions(+), 13 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/max1363.txt

diff --git a/Documentation/devicetree/bindings/iio/max1363.txt b/Documentation/devicetree/bindings/iio/max1363.txt
new file mode 100644
index 0000000..6d22861
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/max1363.txt
@@ -0,0 +1,54 @@
+Device Tree bindings for MAX1363 and compatible ADC controllers
+
+This binding uses the common IIO binding[1].
+
+[1] Documentation/devicetree/bindings/iio/iio-bindings.txt
+
+Required properties:
+
+- compatible, shall be one of the following:
+	"maxim,max1361"
+	"maxim,max1362"
+	"maxim,max1363"
+	"maxim,max1364"
+	"maxim,max1036"
+	"maxim,max1037"
+	"maxim,max1038"
+	"maxim,max1039"
+	"maxim,max1136"
+	"maxim,max1137"
+	"maxim,max1138"
+	"maxim,max1139"
+	"maxim,max1236"
+	"maxim,max1237"
+	"maxim,max1238"
+	"maxim,max1239"
+	"maxim,max11600"
+	"maxim,max11601"
+	"maxim,max11602"
+	"maxim,max11603"
+	"maxim,max11604"
+	"maxim,max11605"
+	"maxim,max11606"
+	"maxim,max11607"
+	"maxim,max11608"
+	"maxim,max11609"
+	"maxim,max11610"
+	"maxim,max11611"
+	"maxim,max11612"
+	"maxim,max11613"
+	"maxim,max11614"
+	"maxim,max11615"
+	"maxim,max11616"
+	"maxim,max11617"
+
+- reg: shall be the I2C device address
+
+Required properties for IIO bindings:
+- #io-channel-cells: from common IIO bindings; shall be set to 1.
+
+Optional properties:
+- vref: Reference voltage in mV. If the provided reference voltage matches
+	the internal reference voltage, the internal reference voltage is used.
+	Otherwise it is assumed that an external reference voltage is used,
+	and the chip is programmed accordingly.
diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
index 51165d6..cf49a20 100644
--- a/drivers/iio/adc/max1363.c
+++ b/drivers/iio/adc/max1363.c
@@ -31,6 +31,7 @@
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/module.h>
+#include <linux/of.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -162,6 +163,7 @@ struct max1363_chip_info {
  * @mask_low:		bitmask for enabled low thresholds
  * @thresh_high:	high threshold values
  * @thresh_low:		low threshold values
+ * @vref_mv:		Actual (external or internal) reference voltage
  */
 struct max1363_state {
 	struct i2c_client		*client;
@@ -181,6 +183,7 @@ struct max1363_state {
 	/* 4x unipolar first then the fours bipolar ones */
 	s16				thresh_high[8];
 	s16				thresh_low[8];
+	u16				vref_mv;
 };
 
 #define MAX1363_MODE_SINGLE(_num, _mask) {				\
@@ -392,6 +395,8 @@ 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);
@@ -399,16 +404,10 @@ 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_mv * 1000) >> st->chip_info->bits;
+		*val = scale_uv / 1000;
+		*val2 = (scale_uv % 1000) * 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
 	default:
 		return -EINVAL;
 	}
@@ -1389,12 +1388,16 @@ 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_mv != st->chip_info->int_vref_mv)
+		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];
@@ -1526,6 +1529,26 @@ static void max1363_buffer_cleanup(struct iio_dev *indio_dev)
 	iio_kfifo_free(indio_dev->buffer);
 }
 
+#ifdef CONFIG_OF
+static int max1363_parse_of(struct device *dev, struct max1363_state *st)
+{
+	struct device_node *np = dev->of_node;
+	u32 vref_mv;
+
+	if (!of_property_read_u32(np, "vref", &vref_mv)) {
+		if (vref_mv == 0 || vref_mv > USHRT_MAX)
+			return -EINVAL;
+		st->vref_mv = vref_mv;
+	}
+	return 0;
+}
+#else
+static int max1363_parse_of(struct device *dev, struct max1363_state *st)
+{
+	return 0;
+}
+#endif
+
 static int max1363_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -1562,6 +1585,11 @@ static int max1363_probe(struct i2c_client *client,
 	st->chip_info = &max1363_chip_info_tbl[id->driver_data];
 	st->client = client;
 
+	st->vref_mv = st->chip_info->int_vref_mv;
+	ret = max1363_parse_of(&client->dev, st);
+	if (ret)
+		goto error_disable_reg;
+
 	ret = max1363_alloc_scan_masks(indio_dev);
 	if (ret)
 		goto error_disable_reg;
-- 
1.7.9.7