[PATCH 3/5] hwmon: ina2xx: allow to change the averaging rate at run-time

[Bartosz Golaszewski <bgolaszewski@baylibre.com>]

The averaging rate of ina226 is hardcoded to 16 in the driver.

Make it modifiable at run-time via a new sysfs attribute.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/hwmon/ina2xx.c | 115 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 106 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index eb66081..0914a72 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -54,6 +54,9 @@
 /* shunt resistor sysfs attribute index */
 #define INA2XX_RSHUNT			0x8
 
+/* INA226 averaging sysfs index */
+#define INA226_AVG			0x9
+
 /* register count */
 #define INA219_REGISTERS		6
 #define INA226_REGISTERS		8
@@ -70,6 +73,12 @@
 /* default shunt resistance */
 #define INA2XX_RSHUNT_DEFAULT		10000
 
+/* bit masks for the averaging setting in the configuration register */
+#define INA226_AVG_RD_MASK		0x0E00
+#define INA226_AVG_WR_MASK		0xF1FF
+
+#define INA226_READ_AVG(reg) ((reg & INA226_AVG_RD_MASK) >> 9)
+
 enum ina2xx_ids { ina219, ina226 };
 
 struct ina2xx_config {
@@ -117,6 +126,13 @@ static const struct ina2xx_config ina2xx_config[] = {
 	},
 };
 
+/* Available averaging rates for ina226. The indices correspond with
+ * the bit values expected by the chip (according to the ina226 datasheet,
+ * table 3 AVG bit settings, found at
+ * http://www.ti.com/lit/ds/symlink/ina226.pdf.
+ */
+static const int ina226_avg_tab[] = { 1, 4, 16, 64, 128, 256, 512, 1024 };
+
 static u16 ina2xx_calibration_val(const struct ina2xx_data *data)
 {
 	return (u16)(data->config->calibration_factor / data->rshunt);
@@ -156,6 +172,45 @@ static int ina2xx_calibrate(const struct i2c_client *client, u16 value)
 	return status;
 }
 
+static int ina226_avg_bits(int avg)
+{
+	int i;
+
+	for (i = 0; i <= ARRAY_SIZE(ina226_avg_tab); i++) {
+		if (avg == ina226_avg_tab[i])
+			return i;
+	}
+
+	/* Invalid value */
+	return -1;
+}
+
+static int ina226_avg_val(int bits)
+{
+	/* Value read from the config register should be correct, but do check
+	 * the boundary just in case.
+	 */
+	if (bits >= ARRAY_SIZE(ina226_avg_tab)) {
+		WARN_ON_ONCE(1);
+		return -1;
+	}
+
+	return ina226_avg_tab[bits];
+}
+
+static inline int ina226_update_avg(struct ina2xx_data *data, int avg)
+{
+	int status;
+	u16 conf;
+
+	mutex_lock(&data->update_lock);
+	conf = (data->regs[INA2XX_CONFIG] & INA226_AVG_WR_MASK) | (avg << 9);
+	status = ina2xx_configure(data->client, conf);
+	mutex_unlock(&data->update_lock);
+
+	return status;
+}
+
 static struct ina2xx_data *ina2xx_update_device(struct device *dev)
 {
 	struct ina2xx_data *data = dev_get_drvdata(dev);
@@ -213,6 +268,10 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg)
 	case INA2XX_RSHUNT:
 		val = data->rshunt;
 		break;
+	case INA226_AVG:
+		val = ina226_avg_val(INA226_READ_AVG(
+					data->regs[INA2XX_CONFIG]));
+		break;
 	default:
 		/* programmer goofed */
 		WARN_ON_ONCE(1);
@@ -236,13 +295,25 @@ static ssize_t ina2xx_show_value(struct device *dev,
 			ina2xx_get_value(data, attr->index));
 }
 
-static ssize_t ina2xx_set_shunt(struct device *dev,
+static ssize_t ina226_show_avg(struct device *dev,
+			       struct device_attribute *da, char *buf)
+{
+	struct ina2xx_data *data = dev_get_drvdata(dev);
+
+	if (data->kind != ina226)
+		return -ENXIO;
+
+	return ina2xx_show_value(dev, da, buf);
+}
+
+static ssize_t ina2xx_set_value(struct device *dev,
 				struct device_attribute *da,
 				const char *buf, size_t count)
 {
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	struct ina2xx_data *data = ina2xx_update_device(dev);
 	long val;
-	s32 status;
+	int status;
 
 	if (IS_ERR(data))
 		return PTR_ERR(data);
@@ -250,12 +321,33 @@ static ssize_t ina2xx_set_shunt(struct device *dev,
 	if ((kstrtol(buf, 10, &val) == -EINVAL) || (val <= 0))
 		return -EINVAL;
 
-	mutex_lock(&data->update_lock);
-	data->rshunt = val;
-	status = ina2xx_calibrate(data->client, ina2xx_calibration_val(data));
-	mutex_unlock(&data->update_lock);
-	if (status < 0)
-		return -ENODEV;
+	switch (attr->index) {
+	case INA2XX_RSHUNT:
+		mutex_lock(&data->update_lock);
+		data->rshunt = val;
+		status = ina2xx_calibrate(data->client,
+					  ina2xx_calibration_val(data));
+		mutex_unlock(&data->update_lock);
+		if (status < 0)
+			return -ENODEV;
+		break;
+	case INA226_AVG:
+		if (data->kind != ina226)
+			return -ENXIO;
+
+		status = ina226_avg_bits(val);
+		if (status < 0)
+			return -EINVAL;
+
+		if (ina226_update_avg(data, status) < 0)
+			return -ENODEV;
+		break;
+	default:
+		/* programmer goofed */
+		WARN_ON_ONCE(1);
+		val = 0;
+		break;
+	}
 
 	return count;
 }
@@ -278,7 +370,11 @@ static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ina2xx_show_value, NULL,
 
 /* shunt resistance */
 static SENSOR_DEVICE_ATTR(rshunt, S_IRUGO | S_IWUSR | S_IWGRP,
-			  ina2xx_show_value, ina2xx_set_shunt, INA2XX_RSHUNT);
+			  ina2xx_show_value, ina2xx_set_value, INA2XX_RSHUNT);
+
+/* averaging rate */
+static SENSOR_DEVICE_ATTR(avg, S_IRUGO | S_IWUSR | S_IWGRP,
+			  ina226_show_avg, ina2xx_set_value, INA226_AVG);
 
 /* pointers to created device attributes */
 static struct attribute *ina2xx_attrs[] = {
@@ -287,6 +383,7 @@ static struct attribute *ina2xx_attrs[] = {
 	&sensor_dev_attr_curr1_input.dev_attr.attr,
 	&sensor_dev_attr_power1_input.dev_attr.attr,
 	&sensor_dev_attr_rshunt.dev_attr.attr,
+	&sensor_dev_attr_avg.dev_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(ina2xx);
-- 
2.1.3