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>

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index e01feba..ffbd60f 100644 (file)
--- a/drivers/hwmon/ina2xx.c
+++ b/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");
+       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;
 }