hwmon: (ina2xx) reinitialize the chip in case it's been reset

Chips from the ina family don't like to be uninitialized. In case the power
is cut-off and restored again the calibration register will be reset
to 0 and both the power and current registers will remain at 0.

Check the calibration register in ina2xx_update_device() and reinitialize
the chip if needed.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ina2xx.c

@@ -35,6 +35,7 @@
 #include <linux/hwmon-sysfs.h>
 #include <linux/jiffies.h>
 #include <linux/of.h>
+#include <linux/delay.h>
 
 #include <linux/platform_data/ina2xx.h>
 
@@ -64,6 +65,9 @@
 
 /* worst case is 68.10 ms (~14.6Hz, ina219) */
 #define INA2XX_CONVERSION_RATE		15
+#define INA2XX_MAX_DELAY		69 /* worst case delay in ms */
+
+#define INA2XX_RSHUNT_DEFAULT		10000
 
 enum ina2xx_ids { ina219, ina226 };
 
@@ -81,6 +85,8 @@ struct ina2xx_data {
 	struct i2c_client *client;
 	const struct ina2xx_config *config;
 
+	long rshunt;
+
 	struct mutex update_lock;
 	bool valid;
 	unsigned long last_updated;
@@ -110,34 +116,96 @@ static const struct ina2xx_config ina2xx_config[] = {
 	},
 };
 
-static struct ina2xx_data *ina2xx_update_device(struct device *dev)
+/*
+ * Initialize the configuration and calibration registers.
+ */
+static int ina2xx_init(struct ina2xx_data *data)
 {
-	struct ina2xx_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->client;
-	struct ina2xx_data *ret = data;
+	int ret;
 
-	mutex_lock(&data->update_lock);
+	/* device configuration */
+	ret = i2c_smbus_write_word_swapped(client, INA2XX_CONFIG,
+					   data->config->config_default);
+	if (ret < 0)
+		return ret;
 
-	if (time_after(jiffies, data->last_updated +
-		       HZ / INA2XX_CONVERSION_RATE) || !data->valid) {
+	/*
+	 * Set current LSB to 1mA, shunt is in uOhms
+	 * (equation 13 in datasheet).
+	 */
+	return i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,
+			data->config->calibration_factor / data->rshunt);
+}
 
-		int i;
+static int ina2xx_do_update(struct device *dev)
+{
+	struct ina2xx_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	int i, rv, retry;
 
 	dev_dbg(&client->dev, "Starting ina2xx update\n");
 
+	for (retry = 5; retry; retry--) {
 		/* Read all registers */
 		for (i = 0; i < data->config->registers; i++) {
-			int rv = i2c_smbus_read_word_swapped(client, i);
-			if (rv < 0) {
-				ret = ERR_PTR(rv);
-				goto abort;
-			}
+			rv = i2c_smbus_read_word_swapped(client, i);
+			if (rv < 0)
+				return rv;
 			data->regs[i] = rv;
 		}
+
+		/*
+		 * If the current value in the calibration register is 0, the
+		 * power and current registers will also remain at 0. In case
+		 * the chip has been reset let's check the calibration
+		 * register and reinitialize if needed.
+		 */
+		if (data->regs[INA2XX_CALIBRATION] == 0) {
+			dev_warn(dev, "chip not calibrated, reinitializing\n");
+
+			rv = ina2xx_init(data);
+			if (rv < 0)
+				return rv;
+
+			/*
+			 * Let's make sure the power and current registers
+			 * have been updated before trying again.
+			 */
+			msleep(INA2XX_MAX_DELAY);
+			continue;
+		}
+
 		data->last_updated = jiffies;
 		data->valid = 1;
+
+		return 0;
 	}
-abort:
+
+	/*
+	 * If we're here then although all write operations succeeded, the
+	 * chip still returns 0 in the calibration register. Nothing more we
+	 * can do here.
+	 */
+	dev_err(dev, "unable to reinitialize the chip\n");
+	return -ENODEV;
+}
+
+static struct ina2xx_data *ina2xx_update_device(struct device *dev)
+{
+	struct ina2xx_data *data = dev_get_drvdata(dev);
+	struct ina2xx_data *ret = data;
+	int rv;
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated +
+		       HZ / INA2XX_CONVERSION_RATE) || !data->valid) {
+		rv = ina2xx_do_update(dev);
+		if (rv < 0)
+			ret = ERR_PTR(rv);
+	}
+
 	mutex_unlock(&data->update_lock);
 	return ret;
 }
@@ -221,7 +289,6 @@ 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;
 
@@ -234,41 +301,28 @@ 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];
+	data->client = client;
 
-	/* device configuration */
-	ret = i2c_smbus_write_word_swapped(client, INA2XX_CONFIG,
-					   data->config->config_default);
-	if (ret < 0) {
-		dev_err(dev,
-			"error writing to the config register: %d", ret);
+	if (data->rshunt <= 0)
 		return -ENODEV;
-	}
 
-	/*
-	 * Set current LSB to 1mA, shunt is in uOhms
-	 * (equation 13 in datasheet).
-	 */
-	ret = i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,
-				data->config->calibration_factor / shunt);
+	ret = ina2xx_init(data);
 	if (ret < 0) {
-		dev_err(dev,
-			"error writing to the calibration register: %d", ret);
+		dev_err(dev, "error configuring the device: %d\n", ret);
 		return -ENODEV;
 	}
 
-	data->client = client;
 	mutex_init(&data->update_lock);
 
 	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
@@ -277,7 +331,7 @@ 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;
 }