linux-kernel - [PATCH-vs-togreg 1/2] iio: ina2xx-adc: update the CALIB. register when RShunt changes

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Date:	Fri, 11 Mar 2016 15:52:29 +0100
From:	Marc Titinger <mtitinger@...libre.com>
To:	jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
	pmeerw@...erw.net
Cc:	afd@...com, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH-vs-togreg 1/2] iio: ina2xx-adc: update the CALIB. register when RShunt changes

The user (or an init script) may setup RShunt via sysfs after the
driver was initialized, for instance based on the EEPROM contents
of a modular probe. The calibration register must be set accordingly.

Signed-off-by: Marc Titinger <marc.titinger@...libre.com>
---
tested with BeagleBone-black and BayLibre-acme.
---
 drivers/iio/adc/ina2xx-adc.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c
index 65909d5..e5ac120 100644
--- a/drivers/iio/adc/ina2xx-adc.c
+++ b/drivers/iio/adc/ina2xx-adc.c
@@ -350,6 +350,23 @@ static ssize_t ina2xx_allow_async_readout_store(struct device *dev,
 	return len;
 }
 
+/*
+ * Set current LSB to 1mA, shunt is in uOhms
+ * (equation 13 in datasheet). We hardcode a Current_LSB
+ * of 1.0 x10-6. The only remaining parameter is RShunt.
+ * There is no need to expose the CALIBRATION register
+ * to the user for now. But we need to reset this register
+ * if the user updates RShunt after driver init, e.g upon
+ * reading an EEPROM/Probe-type value.
+ */
+static int ina2xx_set_calibration(struct ina2xx_chip_info *chip)
+{
+	u16 regval = DIV_ROUND_CLOSEST(chip->config->calibration_factor,
+				   chip->shunt_resistor);
+
+	return regmap_write(chip->regmap, INA2XX_CALIBRATION, regval);
+}
+
 static int set_shunt_resistor(struct ina2xx_chip_info *chip, unsigned int val)
 {
 	if (val <= 0 || val > chip->config->calibration_factor)
@@ -385,6 +402,11 @@ static ssize_t ina2xx_shunt_resistor_store(struct device *dev,
 	if (ret)
 		return ret;
 
+	/* Update the Calibration register */
+	ret = ina2xx_set_calibration(chip);
+	if (ret)
+		return ret;
+
 	return len;
 }
 
@@ -599,6 +621,8 @@ static const struct iio_info ina2xx_info = {
 	.debugfs_reg_access = ina2xx_debug_reg,
 };
 
+
+
 /* Initialize the configuration and calibration registers. */
 static int ina2xx_init(struct ina2xx_chip_info *chip, unsigned int config)
 {
@@ -609,17 +633,7 @@ static int ina2xx_init(struct ina2xx_chip_info *chip, unsigned int config)
 	if (ret)
 		return ret;
 
-	/*
-	 * Set current LSB to 1mA, shunt is in uOhms
-	 * (equation 13 in datasheet). We hardcode a Current_LSB
-	 * of 1.0 x10-6. The only remaining parameter is RShunt.
-	 * There is no need to expose the CALIBRATION register
-	 * to the user for now.
-	 */
-	regval = DIV_ROUND_CLOSEST(chip->config->calibration_factor,
-				   chip->shunt_resistor);
-
-	return regmap_write(chip->regmap, INA2XX_CALIBRATION, regval);
+	return ina2xx_set_calibration(chip);
 }
 
 static int ina2xx_probe(struct i2c_client *client,
-- 
2.5.0