The LM73 supports four A/D conversion resolutions. The default used by the existing lm73 driver is the chip's default, 11-bit (0.25 C/LSB). This patch enables changing of this resolution from userspace via the update_interval sysfs attribute. Full details on usage are included in Documentation/hwmon/lm73. Signed-off-by: Chris Verges <kg4ysn@xxxxxxxxx> --- Documentation/hwmon/lm73 | 78 ++++++++++++++++++++++++++++++++++++ drivers/hwmon/lm73.c | 98 ++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 173 insertions(+), 3 deletions(-) create mode 100644 Documentation/hwmon/lm73 diff --git a/Documentation/hwmon/lm73 b/Documentation/hwmon/lm73 new file mode 100644 index 0000000..56150e1 --- /dev/null +++ b/Documentation/hwmon/lm73 @@ -0,0 +1,78 @@ +Kernel driver lm73 +================== + +Supported chips: + * Texas Instruments LM73 + Prefix: 'lm73' + Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e + Datasheet: Publicly available at the Texas Instruments website + http://www.ti.com/product/lm73 + +Author: Chris Verges <kg4ysn@xxxxxxxxx> + + +Description +----------- + +The LM73 is a digital temperature sensor. All temperature values are +given in degrees Celsius. + +Measurement Resolution Support +------------------------------ + +The LM73 supports four resolutions, defined in terms of degrees C per +LSB: 0.25, 0.125, 0.0625, and 0.3125. Changing the resolution mode +affects the conversion time of the LM73's analog-to-digital converter. +From userspace, the desired resolution can be specified as a function of +conversion time via the 'update_interval' sysfs attribute for the +device. This attribute will normalize ranges of input values to the +maximum times defined for the resolution in the datasheet. + + Resolution Conv. Time Input Range + (C/LSB) (msec) (msec) + -------------------------------------- + 0.25 14 0..14 + 0.125 28 15..28 + 0.0625 56 29..56 + 0.03125 112 57..infinity + -------------------------------------- + +The following examples show how the 'update_interval' attribute can be +used to change the conversion time: + + $ echo 0 > update_interval + $ cat update_interval + 14 + $ cat temp1_input + 24250 + + $ echo 22 > update_interval + $ cat update_interval + 28 + $ cat temp1_input + 24125 + + $ echo 56 > update_interval + $ cat update_interval + 56 + $ cat temp1_input + 24062 + + $ echo 85 > update_interval + $ cat update_interval + 112 + $ cat temp1_input + 24031 + +As shown here, the lm73 driver automatically adjusts any user input for +'update_interval' via a step function. Reading back the +'update_interval' value after a write operation will confirm the +conversion time actively in use. + +Mathematically, the resolution can be derived from the conversion time +via the following function: + + g(x) = 0.250 * [log(x/14) / log(2)] + +where 'x' is the output from 'update_interval' and 'g(x)' is the +resolution in degrees C per LSB. diff --git a/drivers/hwmon/lm73.c b/drivers/hwmon/lm73.c index 7272176..cb3e17a 100644 --- a/drivers/hwmon/lm73.c +++ b/drivers/hwmon/lm73.c @@ -39,8 +39,51 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, #define LM73_TEMP_MIN (-40) #define LM73_TEMP_MAX 150 +#define LM73_CTRL_RES_SHIFT 5 +#define LM73_CTRL_RES_SIZE 2 +#define LM73_CTRL_RES_MASK \ + (((1 << LM73_CTRL_RES_SIZE) - 1) << LM73_CTRL_RES_SHIFT) + +static const unsigned short lm73_convrates[] = { + 14, /* 11-bits (0.25000 C/LSB): RES1 Bit = 0, RES0 Bit = 0 */ + 28, /* 12-bits (0.12500 C/LSB): RES1 Bit = 0, RES0 Bit = 1 */ + 56, /* 13-bits (0.06250 C/LSB): RES1 Bit = 1, RES0 Bit = 0 */ + 112, /* 14-bits (0.03125 C/LSB): RES1 Bit = 1, RES0 Bit = 1 */ +}; + /*-----------------------------------------------------------------------*/ +/* utility functions */ + +static inline s32 lm73_read(struct i2c_client *client, u8 reg) +{ + return i2c_smbus_read_byte_data(client, reg); +} + +static inline s32 lm73_write(struct i2c_client *client, u8 reg, + u8 clear, u8 enable) +{ + s32 tmp = lm73_read(client, reg); + u8 value; + if (tmp < 0) + return tmp; + value = tmp; + value &= ~clear; + value |= enable; + return i2c_smbus_write_byte_data(client, reg, value); +} + +static inline s32 lm73_write_ctrl(struct i2c_client *client, u8 clear, + u8 enable) +{ + /* always clear bits 4:3 and 0 */ + enable &= ~((3 << 3) | (1 << 0)); + return lm73_write(client, LM73_REG_CTRL, + clear | (3 << 3) | (1 << 0), + enable); +} + +/*-----------------------------------------------------------------------*/ static ssize_t set_temp(struct device *dev, struct device_attribute *da, const char *buf, size_t count) @@ -59,7 +102,9 @@ static ssize_t set_temp(struct device *dev, struct device_attribute *da, value = (short) SENSORS_LIMIT(temp/250, (LM73_TEMP_MIN*4), (LM73_TEMP_MAX*4)) << 5; err = i2c_smbus_write_word_swapped(client, attr->index, value); - return (err < 0) ? err : count; + if (err < 0) + return err; + return count; } static ssize_t show_temp(struct device *dev, struct device_attribute *da, @@ -79,6 +124,52 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *da, return scnprintf(buf, PAGE_SIZE, "%d\n", temp); } +static ssize_t set_convrate(struct device *dev, struct device_attribute *da, + const char *buf, size_t count) +{ + struct i2c_client *client = to_i2c_client(dev); + unsigned long convrate; + s32 err; + u8 res_bits = 0; + + err = kstrtoul(buf, 10, &convrate); + if (err < 0) + return err; + + /* + * Convert the desired conversion rate into register bits. + * res_bits is already initialized, and everything past the + * second-to-last value in the array is treated as belonging to + * the last value in the array. + */ + while (res_bits < (ARRAY_SIZE(lm73_convrates) - 1) && + convrate > lm73_convrates[res_bits]) + res_bits++; + + err = lm73_write_ctrl(client, LM73_CTRL_RES_MASK, + res_bits << LM73_CTRL_RES_SHIFT); + if (err < 0) + return err; + + return count; +} + +static ssize_t show_convrate(struct device *dev, struct device_attribute *da, + char *buf) +{ + struct i2c_client *client = to_i2c_client(dev); + s32 ctrl; + u8 res_bits = 0; + + /* Read existing control value */ + ctrl = lm73_read(client, LM73_REG_CTRL); + if (ctrl < 0) + return ctrl; + + res_bits = (ctrl & LM73_CTRL_RES_MASK) >> LM73_CTRL_RES_SHIFT; + return scnprintf(buf, PAGE_SIZE, "%hu\n", + lm73_convrates[res_bits]); +} /*-----------------------------------------------------------------------*/ @@ -90,13 +181,14 @@ static SENSOR_DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, show_temp, set_temp, LM73_REG_MIN); static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp, NULL, LM73_REG_INPUT); - +static SENSOR_DEVICE_ATTR(update_interval, S_IWUSR | S_IRUGO, + show_convrate, set_convrate, 0); static struct attribute *lm73_attributes[] = { &sensor_dev_attr_temp1_input.dev_attr.attr, &sensor_dev_attr_temp1_max.dev_attr.attr, &sensor_dev_attr_temp1_min.dev_attr.attr, - + &sensor_dev_attr_update_interval.dev_attr.attr, NULL }; -- 1.7.9.5 _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
