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hwmon: (sht15) add support for the status register 

* Add support for:
  - Heater.
  - End of battery notice.
  - Ability not to reload from OTP.
  - Low resolution (12bit temp, 8bit humidity).
* Add an utility function to read individual bytes from the device.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
This commit is contained in:
Vivien Didelot 2011-04-12 15:34:38 -04:00 committed by Guenter Roeck
parent 181148ae68
commit cc15c7ebb4
3 changed files with 245 additions and 35 deletions
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29
Documentation/hwmon/sht15
View File

@ -4,6 +4,7 @@ Kernel driver sht15
Authors:
* Wouter Horre
* Jonathan Cameron
* Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Supported chips:
* Sensirion SHT10
@ -30,13 +31,37 @@ Description
The SHT10, SHT11, SHT15, SHT71, and SHT75 are humidity and temperature
sensors.
The devices communicate using two GPIO lines and use the default
resolution settings of 14 bits for temperature and 12 bits for humidity.
The devices communicate using two GPIO lines.
Supported resolutions for the measurements are 14 bits for temperature and 12
bits for humidity, or 12 bits for temperature and 8 bits for humidity.
The humidity calibration coefficients are programmed into an OTP memory on the
chip. These coefficients are used to internally calibrate the signals from the
sensors. Disabling the reload of those coefficients allows saving 10ms for each
measurement and decrease power consumption, while loosing on precision.
Some options may be set directly in the sht15_platform_data structure
or via sysfs attributes.
Note: The regulator supply name is set to "vcc".
Platform data
-------------
* no_otp_reload:
flag to indicate not to reload from OTP (default to false).
* low_resolution:
flag to indicate the temp/humidity resolution to use (default to false).
Sysfs interface
---------------
* temp1_input: temperature input
* humidity1_input: humidity input
* heater_enable: write 1 in this attribute to enable the on-chip heater,
0 to disable it. Be careful not to enable the heater
for too long.
* temp1_fault: if 1, this means that the voltage is low (below 2.47V) and
measurement may be invalid.
* humidity1_fault: same as temp1_fault.

247
drivers/hwmon/sht15.c
View File

@ -1,6 +1,9 @@
/*
* sht15.c - support for the SHT15 Temperature and Humidity Sensor
*
* Portions Copyright (c) 2010-2011 Savoir-faire Linux Inc.
* Vivien Didelot <vivien.didelot@savoirfairelinux.com>
*
* Copyright (c) 2009 Jonathan Cameron
*
* Copyright (c) 2007 Wouter Horre
@ -33,6 +36,8 @@
/* Commands */
#define SHT15_MEASURE_TEMP 0x03
#define SHT15_MEASURE_RH 0x05
#define SHT15_WRITE_STATUS 0x06
#define SHT15_READ_STATUS 0x07
#define SHT15_SOFT_RESET 0x1E
/* Min timings */
@ -41,6 +46,12 @@
#define SHT15_TSU 150 /* (nsecs) data setup time */
#define SHT15_TSRST 11 /* (msecs) soft reset time */
/* Status Register Bits */
#define SHT15_STATUS_LOW_RESOLUTION 0x01
#define SHT15_STATUS_NO_OTP_RELOAD 0x02
#define SHT15_STATUS_HEATER 0x04
#define SHT15_STATUS_LOW_BATTERY 0x40
/* Actions the driver may be doing */
enum sht15_state {
SHT15_READING_NOTHING,
@ -74,9 +85,12 @@ static const struct sht15_temppair temppoints[] = {
* @wait_queue: wait queue for getting values from device.
* @val_temp: last temperature value read from device.
* @val_humid: last humidity value read from device.
* @val_status: last status register value read from device.
* @state: state identifying the action the driver is doing.
* @measurements_valid: are the current stored measures valid (start condition).
* @status_valid: is the current stored status valid (start condition).
* @last_measurement: time of last measure.
* @last_status: time of last status reading.
* @read_lock: mutex to ensure only one read in progress at a time.
* @dev: associate device structure.
* @hwmon_dev: device associated with hwmon subsystem.
@ -97,9 +111,12 @@ struct sht15_data {
wait_queue_head_t wait_queue;
uint16_t val_temp;
uint16_t val_humid;
u8 val_status;
enum sht15_state state;
bool measurements_valid;
bool status_valid;
unsigned long last_measurement;
unsigned long last_status;
struct mutex read_lock;
struct device *dev;
struct device *hwmon_dev;
@ -244,10 +261,105 @@ static int sht15_soft_reset(struct sht15_data *data)
if (ret)
return ret;
msleep(SHT15_TSRST);
/* device resets default hardware status register value */
data->val_status = 0;
return ret;
}
/**
* sht15_end_transmission() - notify device of end of transmission
* @data: device state.
*
* This is basically a NAK (single clock pulse, data high).
*/
static void sht15_end_transmission(struct sht15_data *data)
{
gpio_direction_output(data->pdata->gpio_data, 1);
ndelay(SHT15_TSU);
gpio_set_value(data->pdata->gpio_sck, 1);
ndelay(SHT15_TSCKH);
gpio_set_value(data->pdata->gpio_sck, 0);
ndelay(SHT15_TSCKL);
}
/**
* sht15_read_byte() - Read a byte back from the device
* @data: device state.
*/
static u8 sht15_read_byte(struct sht15_data *data)
{
int i;
u8 byte = 0;
for (i = 0; i < 8; ++i) {
byte <<= 1;
gpio_set_value(data->pdata->gpio_sck, 1);
ndelay(SHT15_TSCKH);
byte |= !!gpio_get_value(data->pdata->gpio_data);
gpio_set_value(data->pdata->gpio_sck, 0);
ndelay(SHT15_TSCKL);
}
return byte;
}
/**
* sht15_send_status() - write the status register byte
* @data: sht15 specific data.
* @status: the byte to set the status register with.
*
* As described in figure 14 and table 5 of the datasheet.
*/
static int sht15_send_status(struct sht15_data *data, u8 status)
{
int ret;
ret = sht15_send_cmd(data, SHT15_WRITE_STATUS);
if (ret)
return ret;
gpio_direction_output(data->pdata->gpio_data, 1);
ndelay(SHT15_TSU);
sht15_send_byte(data, status);
ret = sht15_wait_for_response(data);
if (ret)
return ret;
data->val_status = status;
return 0;
}
/**
* sht15_update_status() - get updated status register from device if too old
* @data: device instance specific data.
*
* As described in figure 15 and table 5 of the datasheet.
*/
static int sht15_update_status(struct sht15_data *data)
{
int ret = 0;
u8 status;
int timeout = HZ;
mutex_lock(&data->read_lock);
if (time_after(jiffies, data->last_status + timeout)
|| !data->status_valid) {
ret = sht15_send_cmd(data, SHT15_READ_STATUS);
if (ret)
goto error_ret;
status = sht15_read_byte(data);
sht15_end_transmission(data);
data->val_status = status;
data->status_valid = true;
data->last_status = jiffies;
}
error_ret:
mutex_unlock(&data->read_lock);
return ret;
}
/**
* sht15_measurement() - get a new value from device
* @data: device instance specific data
@ -324,6 +436,7 @@ static int sht15_update_measurements(struct sht15_data *data)
static inline int sht15_calc_temp(struct sht15_data *data)
{
int d1 = temppoints[0].d1;
int d2 = (data->val_status & SHT15_STATUS_LOW_RESOLUTION) ? 40 : 10;
int i;
for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
@ -336,7 +449,7 @@ static inline int sht15_calc_temp(struct sht15_data *data)
break;
}
return data->val_temp * 10 + d1;
return data->val_temp * d2 + d1;
}
/**
@ -353,18 +466,85 @@ static inline int sht15_calc_humid(struct sht15_data *data)
{
int rh_linear; /* milli percent */
int temp = sht15_calc_temp(data);
int c2, c3;
int t2;
const int c1 = -4;
const int c2 = 40500; /* x 10 ^ -6 */
const int c3 = -28; /* x 10 ^ -7 */
if (data->val_status & SHT15_STATUS_LOW_RESOLUTION) {
c2 = 648000; /* x 10 ^ -6 */
c3 = -7200; /* x 10 ^ -7 */
t2 = 1280;
} else {
c2 = 40500; /* x 10 ^ -6 */
c3 = -28; /* x 10 ^ -7 */
t2 = 80;
}
rh_linear = c1 * 1000
+ c2 * data->val_humid / 1000
+ (data->val_humid * data->val_humid * c3) / 10000;
return (temp - 25000) * (10000 + 80 * data->val_humid)
return (temp - 25000) * (10000 + t2 * data->val_humid)
/ 1000000 + rh_linear;
}
/**
* sht15_show_status() - show status information in sysfs
* @dev: device.
* @attr: device attribute.
* @buf: sysfs buffer where information is written to.
*
* Will be called on read access to temp1_fault, humidity1_fault
* and heater_enable sysfs attributes.
* Returns number of bytes written into buffer, negative errno on error.
*/
static ssize_t sht15_show_status(struct device *dev,
struct device_attribute *attr,
char *buf)
{
int ret;
struct sht15_data *data = dev_get_drvdata(dev);
u8 bit = to_sensor_dev_attr(attr)->index;
ret = sht15_update_status(data);
return ret ? ret : sprintf(buf, "%d\n", !!(data->val_status & bit));
}
/**
* sht15_store_heater() - change heater state via sysfs
* @dev: device.
* @attr: device attribute.
* @buf: sysfs buffer to read the new heater state from.
* @count: length of the data.
*
* Will be called on read access to heater_enable sysfs attribute.
* Returns number of bytes actually decoded, negative errno on error.
*/
static ssize_t sht15_store_heater(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
int ret;
struct sht15_data *data = dev_get_drvdata(dev);
long value;
u8 status;
if (strict_strtol(buf, 10, &value))
return -EINVAL;
mutex_lock(&data->read_lock);
status = data->val_status & 0x07;
if (!!value)
status |= SHT15_STATUS_HEATER;
else
status &= ~SHT15_STATUS_HEATER;
ret = sht15_send_status(data, status);
mutex_unlock(&data->read_lock);
return ret ? ret : count;
}
/**
* sht15_show_temp() - show temperature measurement value in sysfs
* @dev: device.
@ -407,7 +587,6 @@ static ssize_t sht15_show_humidity(struct device *dev,
ret = sht15_update_measurements(data);
return ret ? ret : sprintf(buf, "%d\n", sht15_calc_humid(data));
}
static ssize_t show_name(struct device *dev,
@ -422,10 +601,19 @@ static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
sht15_show_temp, NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
sht15_show_humidity, NULL, 0);
static SENSOR_DEVICE_ATTR(temp1_fault, S_IRUGO, sht15_show_status, NULL,
SHT15_STATUS_LOW_BATTERY);
static SENSOR_DEVICE_ATTR(humidity1_fault, S_IRUGO, sht15_show_status, NULL,
SHT15_STATUS_LOW_BATTERY);
static SENSOR_DEVICE_ATTR(heater_enable, S_IRUGO | S_IWUSR, sht15_show_status,
sht15_store_heater, SHT15_STATUS_HEATER);
static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
static struct attribute *sht15_attrs[] = {
&sensor_dev_attr_temp1_input.dev_attr.attr,
&sensor_dev_attr_humidity1_input.dev_attr.attr,
&sensor_dev_attr_temp1_fault.dev_attr.attr,
&sensor_dev_attr_humidity1_fault.dev_attr.attr,
&sensor_dev_attr_heater_enable.dev_attr.attr,
&dev_attr_name.attr,
NULL,
};
@ -466,25 +654,8 @@ static void sht15_ack(struct sht15_data *data)
gpio_direction_input(data->pdata->gpio_data);
}
/**
* sht15_end_transmission() - notify device of end of transmission
* @data: device state
*
* This is basically a NAK. (single clock pulse, data high)
*/
static void sht15_end_transmission(struct sht15_data *data)
{
gpio_direction_output(data->pdata->gpio_data, 1);
ndelay(SHT15_TSU);
gpio_set_value(data->pdata->gpio_sck, 1);
ndelay(SHT15_TSCKH);
gpio_set_value(data->pdata->gpio_sck, 0);
ndelay(SHT15_TSCKL);
}
static void sht15_bh_read_data(struct work_struct *work_s)
{
int i;
uint16_t val = 0;
struct sht15_data *data
= container_of(work_s, struct sht15_data,
@ -505,16 +676,10 @@ static void sht15_bh_read_data(struct work_struct *work_s)
}
/* Read the data back from the device */
for (i = 0; i < 16; ++i) {
val <<= 1;
gpio_set_value(data->pdata->gpio_sck, 1);
ndelay(SHT15_TSCKH);
val |= !!gpio_get_value(data->pdata->gpio_data);
gpio_set_value(data->pdata->gpio_sck, 0);
ndelay(SHT15_TSCKL);
if (i == 7)
sht15_ack(data);
}
val = sht15_read_byte(data);
val <<= 8;
sht15_ack(data);
val |= sht15_read_byte(data);
/* Tell the device we are done */
sht15_end_transmission(data);
@ -568,6 +733,7 @@ static int __devinit sht15_probe(struct platform_device *pdev)
{
int ret = 0;
struct sht15_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
u8 status = 0;
if (!data) {
ret = -ENOMEM;
@ -588,6 +754,10 @@ static int __devinit sht15_probe(struct platform_device *pdev)
}
data->pdata = pdev->dev.platform_data;
data->supply_uV = data->pdata->supply_mv * 1000;
if (data->pdata->no_otp_reload)
status |= SHT15_STATUS_NO_OTP_RELOAD;
if (data->pdata->low_resolution)
status |= SHT15_STATUS_LOW_RESOLUTION;
/*
* If a regulator is available,
@ -646,6 +816,13 @@ static int __devinit sht15_probe(struct platform_device *pdev)
if (ret)
goto err_release_irq;
/* write status with platform data options */
if (status) {
ret = sht15_send_status(data, status);
if (ret)
goto err_release_irq;
}
ret = sysfs_create_group(&pdev->dev.kobj, &sht15_attr_group);
if (ret) {
dev_err(&pdev->dev, "sysfs create failed\n");
@ -689,6 +866,10 @@ static int __devexit sht15_remove(struct platform_device *pdev)
* prevent new ones beginning
*/
mutex_lock(&data->read_lock);
if (sht15_soft_reset(data)) {
mutex_unlock(&data->read_lock);
return -EFAULT;
}
hwmon_device_unregister(data->hwmon_dev);
sysfs_remove_group(&pdev->dev.kobj, &sht15_attr_group);
if (!IS_ERR(data->reg)) {

4
include/linux/sht15.h
View File

@ -19,10 +19,14 @@
* @gpio_sck: no. of gpio to which the data clock is connected.
* @supply_mv: supply voltage in mv. Overridden by regulator if
* available.
* @no_otp_reload: flag to indicate no reload from OTP.
* @low_resolution: flag to indicate the temp/humidity resolution to use.
*/
struct sht15_platform_data {
int gpio_data;
int gpio_sck;
int supply_mv;
bool no_otp_reload;
bool low_resolution;
};