The DS1621 has an extra register which provides a resolution of 1/16
degree C instead of 1/2 degree C. Make use of it.
Signed-off-by: Jean Delvare <khali at linux-fr.org>
---
drivers/hwmon/ds1621.c | 48 +++++++++++++++++++++++++++++++++++++++---------
1 file changed, 39 insertions(+), 9 deletions(-)
--- linux-2.6.29-rc1.orig/drivers/hwmon/ds1621.c 2009-01-16 15:53:57.000000000 +0100
+++ linux-2.6.29-rc1/drivers/hwmon/ds1621.c 2009-01-16 16:33:28.000000000 +0100
@@ -59,6 +59,8 @@ static const u8 DS1621_REG_TEMP[3] = {
0xA2, /* min, word, RW */
0xA1, /* max, word, RW */
};
+#define DS1621_REG_COUNTER 0xA8
+#define DS1621_REG_SLOPE 0xA9
#define DS1621_REG_CONF 0xAC /* byte, RW */
#define DS1621_COM_START 0xEE /* no data */
#define DS1621_COM_STOP 0x22 /* no data */
@@ -79,15 +81,15 @@ struct ds1621_data {
unsigned long last_updated; /* In jiffies */
unsigned long last_written; /* In jiffies */
- u16 temp[3]; /* Register values, word */
+ s16 temp[3]; /* Register values, word */
u8 conf; /* Register encoding, combined */
+ u8 slope; /* Register value */
};
static int ds1621_probe(struct i2c_client *client,
const struct i2c_device_id *id);
static int ds1621_detect(struct i2c_client *client, int kind,
struct i2c_board_info *info);
-static void ds1621_init_client(struct i2c_client *client);
static int ds1621_remove(struct i2c_client *client);
static struct ds1621_data *ds1621_update_client(struct device *dev);
@@ -111,12 +113,13 @@ static struct i2c_driver ds1621_driver =
.address_data = &addr_data,
};
-/* All registers are word-sized, except for the configuration register.
+/* The temperature value and limit registers are word-sized.
DS1621 uses a high-byte first convention, which is exactly opposite to
the SMBus standard. */
static int ds1621_read_value(struct i2c_client *client, u8 reg)
{
- if (reg == DS1621_REG_CONF)
+ if (reg == DS1621_REG_CONF ||
+ reg == DS1621_REG_COUNTER || reg == DS1621_REG_SLOPE)
return i2c_smbus_read_byte_data(client, reg);
else
return swab16(i2c_smbus_read_word_data(client, reg));
@@ -144,7 +147,7 @@ static int ds1621_write_value(struct i2c
return ret;
}
-static void ds1621_init_client(struct i2c_client *client)
+static int ds1621_init_client(struct i2c_client *client)
{
struct ds1621_data *data = i2c_get_clientdata(client);
int old_reg, reg;
@@ -165,6 +168,15 @@ static void ds1621_init_client(struct i2
/* start conversion */
i2c_smbus_write_byte(client, DS1621_COM_START);
+
+ /* assume that the value of this register never changes */
+ data->slope = ds1621_read_value(client, DS1621_REG_SLOPE);
+ if (data->slope == 0) {
+ dev_err(&client->dev, "Invalid slope value\n");
+ return -ENODEV;
+ }
+
+ return 0;
}
static ssize_t show_temp(struct device *dev, struct device_attribute *da,
@@ -172,8 +184,7 @@ static ssize_t show_temp(struct device *
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
struct ds1621_data *data = ds1621_update_client(dev);
- return sprintf(buf, "%d\n",
- LM75_TEMP_FROM_REG(data->temp[attr->index]));
+ return sprintf(buf, "%d\n", data->temp[attr->index] * 1000 / 256);
}
static ssize_t set_temp(struct device *dev, struct device_attribute *da,
@@ -281,7 +292,9 @@ static int ds1621_probe(struct i2c_clien
mutex_init(&data->update_lock);
/* Initialize the DS1621 chip */
- ds1621_init_client(client);
+ err = ds1621_init_client(client);
+ if (err)
+ goto exit_free;
/* Register sysfs hooks */
if ((err = sysfs_create_group(&client->dev.kobj, &ds1621_group)))
@@ -320,7 +333,8 @@ static struct ds1621_data *ds1621_update
{
struct i2c_client *client = to_i2c_client(dev);
struct ds1621_data *data = i2c_get_clientdata(client);
- u8 new_conf;
+ u8 new_conf, counter;
+ s16 temp;
mutex_lock(&data->update_lock);
@@ -336,6 +350,22 @@ static struct ds1621_data *ds1621_update
data->temp[i] = ds1621_read_value(client,
DS1621_REG_TEMP[i]);
+ /* read the extra resolution bits */
+ counter = ds1621_read_value(client, DS1621_REG_COUNTER);
+ /* There is a small chance that the device updated the
+ registers by the time we read the counter register.
+ So we have to read the temperature register again. */
+ temp = ds1621_read_value(client, DS1621_REG_TEMP[0]);
+ if (temp == data->temp[0]) {
+ /* merge the extra resolution bits */
+ data->temp[0] = (data->temp[0] & 0xff00) + 0xc0
+ - (counter << 8) / data->slope;
+ } else {
+ /* The reading just changed, meaning that we are at
+ the exact boundary between the two values. */
+ data->temp[0] = (data->temp[0] + temp) / 2;
+ }
+
/* reset alarms if necessary */
new_conf = data->conf;
if (data->temp[0] > data->temp[1]) /* input > min */
--
Jean Delvare
