[PATCH v5 1/3] hwmon: ina2xx: make shunt resistance configurable at run-time

Bartosz Golaszewski
2014-12-10T10:39:51Z

The shunt resistance can only be set via platform_data or device tree. This
isn't suitable for devices in which the shunt resistance can change/isn't
known at boot-time.

Add a sysfs attribute that allows to read and set the shunt resistance.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/hwmon/ina2xx.c | 74 ++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 65 insertions(+), 9 deletions(-)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index e01feba..6e73add 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -51,7 +51,6 @@
#define INA226_ALERT_LIMIT 0x07
#define INA226_DIE_ID 0xFF

-
/* register count */
#define INA219_REGISTERS 6
#define INA226_REGISTERS 8
@@ -65,6 +64,9 @@
/* worst case is 68.10 ms (~14.6Hz, ina219) */
#define INA2XX_CONVERSION_RATE 15

+/* default shunt resistance */
+#define INA2XX_RSHUNT_DEFAULT 10000
+
enum ina2xx_ids { ina219, ina226 };

struct ina2xx_config {
@@ -87,6 +89,8 @@ struct ina2xx_data {

int kind;
u16 regs[INA2XX_MAX_REGISTERS];
+
+ long rshunt;
};

static const struct ina2xx_config ina2xx_config[] = {
@@ -110,6 +114,11 @@ static const struct ina2xx_config ina2xx_config[] = {
},
};

+static u16 ina2xx_calibration_val(const struct ina2xx_data *data)
+{
+ return data->config->calibration_factor / data->rshunt;
+}
+
static struct ina2xx_data *ina2xx_update_device(struct device *dev)
{
struct ina2xx_data *data = dev_get_drvdata(dev);
@@ -164,6 +173,13 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg)
/* signed register, LSB=1mA (selected), in mA */
val = (s16)data->regs[reg];
break;
+ case INA2XX_CALIBRATION:
+ if (data->regs[reg] == 0)
+ val = 0;
+ else
+ val = data->config->calibration_factor
+ / data->regs[reg];
+ break;
default:
/* programmer goofed */
WARN_ON_ONCE(1);
@@ -187,6 +203,38 @@ static ssize_t ina2xx_show_value(struct device *dev,
ina2xx_get_value(data, attr->index));
}

+static ssize_t ina2xx_set_shunt(struct device *dev,
+ struct device_attribute *da,
+ const char *buf, size_t count)
+{
+ struct ina2xx_data *data = ina2xx_update_device(dev);
+ unsigned long val;
+ int status;
+
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ status = kstrtoul(buf, 10, &val);
+ if (status < 0)
+ return status;
+
+ if (val == 0 ||
+ /* Values greater than the calibration factor make no sense. */
+ val > data->config->calibration_factor ||
+ val > LONG_MAX)
+ return -EINVAL;
+
+ mutex_lock(&data->update_lock);
+ data->rshunt = val;
+ status = i2c_smbus_write_word_swapped(data->client, INA2XX_CALIBRATION,
+ ina2xx_calibration_val(data));
+ mutex_unlock(&data->update_lock);
+ if (status < 0)
+ return status;
+
+ return count;
+}
+
/* shunt voltage */
static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ina2xx_show_value, NULL,
INA2XX_SHUNT_VOLTAGE);
@@ -203,12 +251,18 @@ static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ina2xx_show_value, NULL,
static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ina2xx_show_value, NULL,
INA2XX_POWER);

+/* shunt resistance */
+static SENSOR_DEVICE_ATTR(shunt_resistor, S_IRUGO | S_IWUSR,
+ ina2xx_show_value, ina2xx_set_shunt,
+ INA2XX_CALIBRATION);
+
/* pointers to created device attributes */
static struct attribute *ina2xx_attrs[] = {
&sensor_dev_attr_in0_input.dev_attr.attr,
&sensor_dev_attr_in1_input.dev_attr.attr,
&sensor_dev_attr_curr1_input.dev_attr.attr,
&sensor_dev_attr_power1_input.dev_attr.attr,
+ &sensor_dev_attr_shunt_resistor.dev_attr.attr,
NULL,
};
ATTRIBUTE_GROUPS(ina2xx);
@@ -221,7 +275,6 @@ static int ina2xx_probe(struct i2c_client *client,
struct device *dev = &client->dev;
struct ina2xx_data *data;
struct device *hwmon_dev;
- long shunt = 10000; /* default shunt value 10mOhms */
u32 val;
int ret;

@@ -234,19 +287,22 @@ static int ina2xx_probe(struct i2c_client *client,

if (dev_get_platdata(dev)) {
pdata = dev_get_platdata(dev);
- shunt = pdata->shunt_uohms;
+ data->rshunt = pdata->shunt_uohms;
} else if (!of_property_read_u32(dev->of_node,
"shunt-resistor", &val)) {
- shunt = val;
+ data->rshunt = val;
+ } else {
+ data->rshunt = INA2XX_RSHUNT_DEFAULT;
}

- if (shunt <= 0)
- return -ENODEV;
-
/* set the device type */
data->kind = id->driver_data;
data->config = &ina2xx_config[data->kind];

+ if (data->rshunt <= 0 ||
+ data->rshunt > data->config->calibration_factor)
+ return -ENODEV;
+
/* device configuration */
ret = i2c_smbus_write_word_swapped(client, INA2XX_CONFIG,
data->config->config_default);
@@ -261,7 +317,7 @@ static int ina2xx_probe(struct i2c_client *client,
* (equation 13 in datasheet).
*/
ret = i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,
- data->config->calibration_factor / shunt);
+ ina2xx_calibration_val(data));
if (ret < 0) {
dev_err(dev,
"error writing to the calibration register: %d", ret);
@@ -277,7 +333,7 @@ static int ina2xx_probe(struct i2c_client *client,
return PTR_ERR(hwmon_dev);

dev_info(dev, "power monitor %s (Rshunt = %li uOhm)\n",
- id->name, shunt);
+ id->name, data->rshunt);

return 0;
}
--
2.1.3