hwmon: (lm83) Use regmap

Using local caching in this driver had few benefits. It used cached values
for two seconds and then re-read all registers from the chip even if the
user only accessed a single attribute. On top of that, alarm attributes
were stale for up to four seconds (the first status register read reports
and clears an alarm, the second reports it cleared). Use regmap instead
for caching. Do not re-read non-volatile registers, and do not cache
volatile registers.

As part of this change, handle register read and write address differences
in regmap code. This is necessary to avoid problems with caching in the
regmap core, and ultimately simplifies the code.

Also, errors observed when reading from and writing to registers are no
longer ignored.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/Kconfig

@@ -1288,6 +1288,7 @@ config SENSORS_LM80
 config SENSORS_LM83
 	tristate "National Semiconductor LM83 and compatibles"
 	depends on I2C
+	select REGMAP
 	help
 	  If you say yes here you get support for National Semiconductor
 	  LM82 and LM83 sensor chips.

drivers/hwmon/lm83.c

@@ -21,11 +21,11 @@
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
-#include <linux/jiffies.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 
@@ -77,7 +77,7 @@ enum chips { lm83, lm82 };
 				 (val) < 0 ? ((val) - 500) / 1000 : \
 				 ((val) + 500) / 1000)
 
-static const u8 LM83_REG_R_TEMP[] = {
+static const u8 LM83_REG_TEMP[] = {
 	LM83_REG_R_LOCAL_TEMP,
 	LM83_REG_R_REMOTE1_TEMP,
 	LM83_REG_R_REMOTE2_TEMP,
@@ -89,62 +89,82 @@ static const u8 LM83_REG_R_TEMP[] = {
 	LM83_REG_R_TCRIT,
 };
 
-static const u8 LM83_REG_W_HIGH[] = {
-	LM83_REG_W_LOCAL_HIGH,
-	LM83_REG_W_REMOTE1_HIGH,
-	LM83_REG_W_REMOTE2_HIGH,
-	LM83_REG_W_REMOTE3_HIGH,
-	LM83_REG_W_TCRIT,
-};
-
 /*
  * Client data (each client gets its own)
  */
 
 struct lm83_data {
-	struct i2c_client *client;
+	struct regmap *regmap;
 	const struct attribute_group *groups[3];
-	struct mutex update_lock;
-	bool valid; /* false until following fields are valid */
-	unsigned long last_updated; /* in jiffies */
-
-	/* registers values */
-	s8 temp[9];	/* 0..3: input 1-4,
-			   4..7: high limit 1-4,
-			   8   : critical limit */
-	u16 alarms; /* bitvector, combined */
 };
 
-static struct lm83_data *lm83_update_device(struct device *dev)
+/* regmap code */
+
+static int lm83_regmap_reg_read(void *context, unsigned int reg, unsigned int *val)
 {
-	struct lm83_data *data = dev_get_drvdata(dev);
-	struct i2c_client *client = data->client;
+	struct i2c_client *client = context;
+	int ret;
 
-	mutex_lock(&data->update_lock);
+	ret = i2c_smbus_read_byte_data(client, reg);
+	if (ret < 0)
+		return ret;
 
-	if (time_after(jiffies, data->last_updated + HZ * 2) || !data->valid) {
-		int nr;
+	*val = ret;
+	return 0;
+}
 
-		dev_dbg(&client->dev, "Updating lm83 data.\n");
-		for (nr = 0; nr < 9; nr++) {
-			data->temp[nr] =
-			    i2c_smbus_read_byte_data(client,
-			    LM83_REG_R_TEMP[nr]);
-		}
-		data->alarms =
-		    i2c_smbus_read_byte_data(client, LM83_REG_R_STATUS1)
-		    + (i2c_smbus_read_byte_data(client, LM83_REG_R_STATUS2)
-		    << 8);
+/*
+ * The regmap write function maps read register addresses to write register
+ * addresses. This is necessary for regmap register caching to work.
+ * An alternative would be to clear the regmap cache whenever a register is
+ * written, but that would be much more expensive.
+ */
+static int lm83_regmap_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct i2c_client *client = context;
 
-		data->last_updated = jiffies;
-		data->valid = true;
+	switch (reg) {
+	case LM83_REG_R_CONFIG:
+	case LM83_REG_R_LOCAL_HIGH:
+	case LM83_REG_R_REMOTE2_HIGH:
+		reg += 0x06;
+		break;
+	case LM83_REG_R_REMOTE1_HIGH:
+	case LM83_REG_R_REMOTE3_HIGH:
+	case LM83_REG_R_TCRIT:
+		reg += 0x18;
+		break;
+	default:
+		break;
 	}
 
-	mutex_unlock(&data->update_lock);
-
-	return data;
+	return i2c_smbus_write_byte_data(client, reg, val);
 }
 
+static bool lm83_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case LM83_REG_R_LOCAL_TEMP:
+	case LM83_REG_R_REMOTE1_TEMP:
+	case LM83_REG_R_REMOTE2_TEMP:
+	case LM83_REG_R_REMOTE3_TEMP:
+	case LM83_REG_R_STATUS1:
+	case LM83_REG_R_STATUS2:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct regmap_config lm83_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_RBTREE,
+	.volatile_reg = lm83_regmap_is_volatile,
+	.reg_read = lm83_regmap_reg_read,
+	.reg_write = lm83_regmap_reg_write,
+};
+
 /*
  * Sysfs stuff
  */
@@ -153,8 +173,15 @@ static ssize_t temp_show(struct device *dev, struct device_attribute *devattr,
 			 char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
-	struct lm83_data *data = lm83_update_device(dev);
-	return sprintf(buf, "%d\n", TEMP_FROM_REG(data->temp[attr->index]));
+	struct lm83_data *data = dev_get_drvdata(dev);
+	unsigned int regval;
+	int ret;
+
+	ret = regmap_read(data->regmap, LM83_REG_TEMP[attr->index], &regval);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%d\n", TEMP_FROM_REG((s8)regval));
 }
 
 static ssize_t temp_store(struct device *dev,
@@ -163,38 +190,57 @@ static ssize_t temp_store(struct device *dev,
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 	struct lm83_data *data = dev_get_drvdata(dev);
-	struct i2c_client *client = data->client;
+	unsigned int regval;
 	long val;
-	int nr = attr->index;
 	int err;
 
 	err = kstrtol(buf, 10, &val);
 	if (err < 0)
 		return err;
 
-	mutex_lock(&data->update_lock);
-	data->temp[nr] = TEMP_TO_REG(val);
-	i2c_smbus_write_byte_data(client, LM83_REG_W_HIGH[nr - 4],
-				  data->temp[nr]);
-	mutex_unlock(&data->update_lock);
-	return count;
+	regval = TEMP_TO_REG(val);
+	err = regmap_write(data->regmap, LM83_REG_TEMP[attr->index], regval);
+	return err ? : count;
 }
 
 static ssize_t alarms_show(struct device *dev, struct device_attribute *dummy,
 			   char *buf)
 {
-	struct lm83_data *data = lm83_update_device(dev);
-	return sprintf(buf, "%d\n", data->alarms);
+	struct lm83_data *data = dev_get_drvdata(dev);
+	unsigned int alarms, regval;
+	int err;
+
+	err = regmap_read(data->regmap, LM83_REG_R_STATUS1, &regval);
+	if (err < 0)
+		return err;
+	alarms = regval;
+	err = regmap_read(data->regmap, LM83_REG_R_STATUS2, &regval);
+	if (err < 0)
+		return err;
+	alarms |= regval << 8;
+
+	return sprintf(buf, "%u\n", alarms);
 }
 
 static ssize_t alarm_show(struct device *dev,
 			  struct device_attribute *devattr, char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
-	struct lm83_data *data = lm83_update_device(dev);
+	struct lm83_data *data = dev_get_drvdata(dev);
 	int bitnr = attr->index;
+	unsigned int alarm;
+	int reg, err;
 
-	return sprintf(buf, "%d\n", (data->alarms >> bitnr) & 1);
+	if (bitnr < 8) {
+		reg = LM83_REG_R_STATUS1;
+	} else {
+		reg = LM83_REG_R_STATUS2;
+		bitnr -= 8;
+	}
+	err = regmap_read(data->regmap, reg, &alarm);
+	if (err < 0)
+		return err;
+	return sprintf(buf, "%d\n", (alarm >> bitnr) & 1);
 }
 
 static SENSOR_DEVICE_ATTR_RO(temp1_input, temp, 0);
@@ -326,16 +372,17 @@ MODULE_DEVICE_TABLE(i2c, lm83_id);
 
 static int lm83_probe(struct i2c_client *client)
 {
+	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	struct lm83_data *data;
 
-	data = devm_kzalloc(&client->dev, sizeof(struct lm83_data),
-			    GFP_KERNEL);
+	data = devm_kzalloc(dev, sizeof(struct lm83_data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 
-	data->client = client;
-	mutex_init(&data->update_lock);
+	data->regmap = devm_regmap_init(dev, NULL, client, &lm83_regmap_config);
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
 
 	/*
 	 * Register sysfs hooks
@@ -347,8 +394,7 @@ static int lm83_probe(struct i2c_client *client)
 	if (i2c_match_id(lm83_id, client)->driver_data == lm83)
 		data->groups[1] = &lm83_group_opt;
 
-	hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
-							   client->name,
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 							   data, data->groups);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }