[PATCH v5 2/3] hwmon: ina2xx: allow to change the averaging rate at run-time

Bartosz Golaszewski
2014-12-10T10:39:17Z

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 | 125 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 122 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index 6e73add..b86474e 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -67,6 +67,15 @@
/* 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)
+
+/* common attrs, ina226 attrs and NULL */
+#define INA2XX_MAX_ATTRIBUTE_GROUPS 3
+
enum ina2xx_ids { ina219, ina226 };

struct ina2xx_config {
@@ -88,6 +97,7 @@ struct ina2xx_data {
unsigned long last_updated;

int kind;
+ const struct attribute_group *groups[INA2XX_MAX_ATTRIBUTE_GROUPS];
u16 regs[INA2XX_MAX_REGISTERS];

long rshunt;
@@ -114,11 +124,43 @@ 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 data->config->calibration_factor / data->rshunt;
}

+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;
+ }
+
+ return -EINVAL;
+}
+
+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))
+ return -ENODEV;
+
+ return ina226_avg_tab[bits];
+}
+
static struct ina2xx_data *ina2xx_update_device(struct device *dev)
{
struct ina2xx_data *data = dev_get_drvdata(dev);
@@ -235,6 +277,63 @@ static ssize_t ina2xx_set_shunt(struct device *dev,
return count;
}

+static ssize_t ina226_show_avg(struct device *dev,
+ struct device_attribute *da, char *buf)
+{
+ struct ina2xx_data *data = ina2xx_update_device(dev);
+ int avg, i, written = 0;
+ const char *fmt;
+
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ avg = ina226_avg_val(INA226_READ_AVG(data->regs[INA2XX_CONFIG]));
+ if (avg < 0)
+ return avg;
+
+ for (i = 0; i < ARRAY_SIZE(ina226_avg_tab); i++) {
+ if (avg == ina226_avg_tab[i])
+ fmt = "\t[%d]";
+ else
+ fmt = "\t%d";
+
+ written += snprintf(buf + written, PAGE_SIZE - written,
+ fmt, ina226_avg_tab[i]);
+ }
+ written += snprintf(buf + written, PAGE_SIZE - written, "\n");
+
+ return written;
+}
+
+static ssize_t ina226_set_avg(struct device *dev,
+ struct device_attribute *da,
+ const char *buf, size_t count)
+{
+ struct ina2xx_data *data = ina2xx_update_device(dev);
+ long val;
+ int status, avg;
+ u16 conf;
+
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ status = kstrtol(buf, 10, &val);
+ if (status < 0)
+ return status;
+
+ avg = ina226_avg_bits(val);
+ if (avg < 0)
+ return avg;
+
+ mutex_lock(&data->update_lock);
+ conf = (data->regs[INA2XX_CONFIG] & INA226_AVG_WR_MASK) | (avg << 9);
+ status = i2c_smbus_write_word_swapped(data->client,
+ INA2XX_CONFIG, conf);
+ mutex_unlock(&data->update_lock);
+
+ return count;
+}
+
/* shunt voltage */
static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ina2xx_show_value, NULL,
INA2XX_SHUNT_VOLTAGE);
@@ -256,6 +355,10 @@ static SENSOR_DEVICE_ATTR(shunt_resistor, S_IRUGO | S_IWUSR,
ina2xx_show_value, ina2xx_set_shunt,
INA2XX_CALIBRATION);

+/* averaging rate */
+static SENSOR_DEVICE_ATTR(avg_rate, S_IRUGO | S_IWUSR,
+ ina226_show_avg, ina226_set_avg, 0);
+
/* pointers to created device attributes */
static struct attribute *ina2xx_attrs[] = {
&sensor_dev_attr_in0_input.dev_attr.attr,
@@ -265,7 +368,19 @@ static struct attribute *ina2xx_attrs[] = {
&sensor_dev_attr_shunt_resistor.dev_attr.attr,
NULL,
};
-ATTRIBUTE_GROUPS(ina2xx);
+
+static const struct attribute_group ina2xx_group = {
+ .attrs = ina2xx_attrs,
+};
+
+static struct attribute *ina226_attrs[] = {
+ &sensor_dev_attr_avg_rate.dev_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group ina226_group = {
+ .attrs = ina226_attrs,
+};

static int ina2xx_probe(struct i2c_client *client,
const struct i2c_device_id *id)
@@ -276,7 +391,7 @@ static int ina2xx_probe(struct i2c_client *client,
struct ina2xx_data *data;
struct device *hwmon_dev;
u32 val;
- int ret;
+ int ret, group = 0;

if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA))
return -ENODEV;
@@ -327,8 +442,12 @@ static int ina2xx_probe(struct i2c_client *client,
data->client = client;
mutex_init(&data->update_lock);

+ data->groups[group++] = &ina2xx_group;
+ if (data->kind == ina226)
+ data->groups[group++] = &ina226_group;
+
hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
- data, ina2xx_groups);
+ data, data->groups);
if (IS_ERR(hwmon_dev))
return PTR_ERR(hwmon_dev);

--
2.1.3