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Subject[PATCH 2/2] iio: afe: unit-converter: add support for adi,lt6106
Date
This is a current sense amplifier from Analog Devices.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
drivers/iio/afe/Kconfig | 3 +-
drivers/iio/afe/iio-unit-converter.c | 54 ++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/afe/Kconfig b/drivers/iio/afe/Kconfig
index 642ce4eb12a6..0e10fe8f459a 100644
--- a/drivers/iio/afe/Kconfig
+++ b/drivers/iio/afe/Kconfig
@@ -10,7 +10,8 @@ config IIO_UNIT_CONVERTER
depends on OF || COMPILE_TEST
help
Say yes here to build support for the IIO unit converter
- that handles voltage dividers and current sense shunts.
+ that handles voltage dividers, current sense shunts and
+ the LT6106 Current Sense Amplifier from Analog Devices.

To compile this driver as a module, choose M here: the
module will be called iio-unit-converter.
diff --git a/drivers/iio/afe/iio-unit-converter.c b/drivers/iio/afe/iio-unit-converter.c
index fc50290d7e5e..4b0ae5ab9c2d 100644
--- a/drivers/iio/afe/iio-unit-converter.c
+++ b/drivers/iio/afe/iio-unit-converter.c
@@ -144,6 +144,53 @@ static int unit_converter_configure_channel(struct device *dev,
return 0;
}

+static int unit_converter_adi_lt6106_props(struct device *dev,
+ struct unit_converter *uc)
+{
+ u32 sense;
+ u32 rin;
+ u32 rout;
+ u32 factor;
+ int ret;
+
+ ret = device_property_read_u32(dev, "sense-resistor-micro-ohms",
+ &sense);
+ if (ret) {
+ dev_err(dev, "failed to read the sense resistance: %d\n", ret);
+ return ret;
+ }
+
+ ret = device_property_read_u32(dev, "input-resistor-ohms", &rin);
+ if (ret) {
+ dev_err(dev, "failed to read the input resistance: %d\n", ret);
+ return ret;
+ }
+
+ ret = device_property_read_u32(dev, "output-resistor-ohms", &rout);
+ if (ret) {
+ dev_err(dev, "failed to read the output resistance: %d\n", ret);
+ return ret;
+ }
+
+ /*
+ * Calculate the scaling factor, rin / (rout * sense), while trying
+ * to keep the fraction from overflowing.
+ */
+ factor = gcd(sense, 1000000);
+ uc->numerator = 1000000 / factor;
+ uc->denominator = sense / factor;
+
+ factor = gcd(uc->numerator, rout);
+ uc->numerator /= factor;
+ uc->denominator *= rout / factor;
+
+ factor = gcd(uc->denominator, rin);
+ uc->numerator *= rin / factor;
+ uc->denominator /= factor;
+
+ return 0;
+}
+
static int unit_converter_current_sense_shunt_props(struct device *dev,
struct unit_converter *uc)
{
@@ -175,11 +222,16 @@ static int unit_converter_voltage_divider_props(struct device *dev,
}

enum unit_converter_variant {
+ ADI_LT6106,
CURRENT_SENSE_SHUNT,
VOLTAGE_DIVIDER,
};

static const struct unit_converter_cfg unit_converter_cfg[] = {
+ [ADI_LT6106] = {
+ .type = IIO_CURRENT,
+ .props = unit_converter_adi_lt6106_props,
+ },
[CURRENT_SENSE_SHUNT] = {
.type = IIO_CURRENT,
.props = unit_converter_current_sense_shunt_props,
@@ -191,6 +243,8 @@ static const struct unit_converter_cfg unit_converter_cfg[] = {
};

static const struct of_device_id unit_converter_match[] = {
+ { .compatible = "adi,lt6106",
+ .data = &unit_converter_cfg[ADI_LT6106], },
{ .compatible = "current-sense-shunt",
.data = &unit_converter_cfg[CURRENT_SENSE_SHUNT], },
{ .compatible = "voltage-divider",
--
2.11.0
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