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 temp1_update_interval attribute. Full details on use of this mechanism are described in Documentation/hwmon/lm73. Signed-off-by: Chris Verges <kg4ysn@xxxxxxxxx> --- Documentation/hwmon/lm73 | 78 ++++++++++++++++++++++++++++++++++++++++++++++ drivers/hwmon/lm73.c | 76 +++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 150 insertions(+), 4 deletions(-) create mode 100644 Documentation/hwmon/lm73 diff --git a/Documentation/hwmon/lm73 b/Documentation/hwmon/lm73 new file mode 100644 index 0000000..2d947d3 --- /dev/null +++ b/Documentation/hwmon/lm73 @@ -0,0 +1,78 @@ +Kernel driver lm90 +================== + +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..21 + 0.125 28 22..42 + 0.0625 56 43..84 + 0.03125 112 85..infinity + -------------------------------------- + +The following examples show how the 'update_interval' attribute can be +used to change the conversion time: + + $ echo 0 > temp1_update_interval + $ cat temp1_update_interval + 14 + $ cat temp1_input + 24250 + + $ echo 36 > temp1_update_interval + $ cat temp1_update_interval + 28 + $ cat temp1_input + 24125 + + $ echo 56 > temp1_update_interval + $ cat temp1_update_interval + 56 + $ cat temp1_input + 24062 + + $ echo 85 > temp1_update_interval + $ cat temp1_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..f443fad 100644 --- a/drivers/hwmon/lm73.c +++ b/drivers/hwmon/lm73.c @@ -21,7 +21,6 @@ #include <linux/hwmon-sysfs.h> #include <linux/err.h> - /* Addresses scanned */ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4c, 0x4d, 0x4e, I2C_CLIENT_END }; @@ -39,8 +38,20 @@ 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) +#define SCALE_150_PERCENT(x) (((x) * 150) / 100) + +static const unsigned short lm73_valid_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 */ +}; + +/*-----------------------------------------------------------------------*/ static ssize_t set_temp(struct device *dev, struct device_attribute *da, const char *buf, size_t count) @@ -79,6 +90,62 @@ 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; + u8 value; + + err = kstrtoul(buf, 10, &convrate); + if (err < 0) + return err; + + /* Read existing control value */ + err = i2c_smbus_read_byte_data(client, LM73_REG_CTRL); + if (err < 0) + return err; + value = err; + + /* Convert the desired conversion rate into register bits */ + if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[0])) + res_bits = 0; + else if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[1])) + res_bits = 1; + else if (convrate < SCALE_150_PERCENT(lm73_valid_convrates[2])) + res_bits = 2; + else + res_bits = 3; + + /* Create the new control register value */ + value &= ~(LM73_CTRL_RES_MASK << LM73_CTRL_RES_SHIFT); + value |= (res_bits << LM73_CTRL_RES_SHIFT); + + /* Write value */ + err = i2c_smbus_write_byte_data(client, LM73_REG_CTRL, value); + 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); + uint32_t ctrl; + u8 res_bits = 0; + + /* Read existing control value */ + ctrl = i2c_smbus_read_byte_data(client, LM73_REG_CTRL); + if (ctrl < 0) + return ctrl; + + res_bits = (ctrl >> LM73_CTRL_RES_SHIFT) & LM73_CTRL_RES_MASK; + return scnprintf(buf, PAGE_SIZE, "%hu\n", + lm73_valid_convrates[res_bits]); +} /*-----------------------------------------------------------------------*/ @@ -90,13 +157,14 @@ 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(temp1_update_interval, S_IWUSR | S_IRUGO, + show_convrate, set_convrate, LM73_REG_CTRL); 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_temp1_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
