w1: add ability to set (SRAM) and store (EEPROM) configuration for temp sensors like DS18B20
Since many temperature sensors come "preconfigured" with a lower precision, people are stuck at that precision when running on a kernel based device (unlike the Dallas 1Wire library for e.g. Arduino, which supports writing the configuration/scratchpad). This patch adds write support for the scratchpad/precision registers via w1_slave sysfs. Signed-off-by: Ben Sen <0.x29a.0@gmail.com> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Sen
Greg Kroah-Hartman
parent
ae53e37400
commit
0a19f129d7
3 changed files with 222 additions and 8 deletions
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@ -33,7 +33,15 @@ temperature conversion at a time. If none of the devices are parasite
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powered it would be possible to convert all the devices at the same
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time and then go back to read individual sensors. That isn't
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currently supported. The driver also doesn't support reduced
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precision (which would also reduce the conversion time).
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precision (which would also reduce the conversion time) when reading values.
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Writing a value between 9 and 12 to the sysfs w1_slave file will change the
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precision of the sensor for the next readings. This value is in (volatile)
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SRAM, so it is reset when the sensor gets power-cycled.
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To store the current precision configuration into EEPROM, the value 0
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has to be written to the sysfs w1_slave file. Since the EEPROM has a limited
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amount of writes (>50k), this command should be used wisely.
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The module parameter strong_pullup can be set to 0 to disable the
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strong pullup, 1 to enable autodetection or 2 to force strong pullup.
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@ -92,10 +92,13 @@ static void w1_therm_remove_slave(struct w1_slave *sl)
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static ssize_t w1_slave_show(struct device *device,
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struct device_attribute *attr, char *buf);
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static ssize_t w1_slave_store(struct device *device,
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struct device_attribute *attr, const char *buf, size_t size);
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static ssize_t w1_seq_show(struct device *device,
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struct device_attribute *attr, char *buf);
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static DEVICE_ATTR_RO(w1_slave);
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static DEVICE_ATTR_RW(w1_slave);
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static DEVICE_ATTR_RO(w1_seq);
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static struct attribute *w1_therm_attrs[] = {
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@ -154,8 +157,17 @@ struct w1_therm_family_converter
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u16 reserved;
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struct w1_family *f;
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int (*convert)(u8 rom[9]);
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int (*precision)(struct device *device, int val);
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int (*eeprom)(struct device *device);
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};
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/* write configuration to eeprom */
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static inline int w1_therm_eeprom(struct device *device);
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/* Set precision for conversion */
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static inline int w1_DS18B20_precision(struct device *device, int val);
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static inline int w1_DS18S20_precision(struct device *device, int val);
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/* The return value is millidegrees Centigrade. */
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static inline int w1_DS18B20_convert_temp(u8 rom[9]);
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static inline int w1_DS18S20_convert_temp(u8 rom[9]);
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@ -163,26 +175,194 @@ static inline int w1_DS18S20_convert_temp(u8 rom[9]);
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static struct w1_therm_family_converter w1_therm_families[] = {
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{
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.f = &w1_therm_family_DS18S20,
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.convert = w1_DS18S20_convert_temp
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.convert = w1_DS18S20_convert_temp,
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.precision = w1_DS18S20_precision,
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.eeprom = w1_therm_eeprom
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},
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{
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.f = &w1_therm_family_DS1822,
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.convert = w1_DS18B20_convert_temp
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.convert = w1_DS18B20_convert_temp,
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.precision = w1_DS18S20_precision,
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.eeprom = w1_therm_eeprom
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},
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{
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.f = &w1_therm_family_DS18B20,
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.convert = w1_DS18B20_convert_temp
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.convert = w1_DS18B20_convert_temp,
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.precision = w1_DS18B20_precision,
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.eeprom = w1_therm_eeprom
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},
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{
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.f = &w1_therm_family_DS28EA00,
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.convert = w1_DS18B20_convert_temp
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.convert = w1_DS18B20_convert_temp,
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.precision = w1_DS18S20_precision,
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.eeprom = w1_therm_eeprom
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},
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{
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.f = &w1_therm_family_DS1825,
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.convert = w1_DS18B20_convert_temp
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.convert = w1_DS18B20_convert_temp,
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.precision = w1_DS18S20_precision,
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.eeprom = w1_therm_eeprom
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}
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};
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static inline int w1_therm_eeprom(struct device *device)
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{
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struct w1_slave *sl = dev_to_w1_slave(device);
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struct w1_master *dev = sl->master;
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u8 rom[9], external_power;
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int ret, max_trying = 10;
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u8 *family_data = sl->family_data;
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ret = mutex_lock_interruptible(&dev->bus_mutex);
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if (ret != 0)
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goto post_unlock;
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if (!sl->family_data) {
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ret = -ENODEV;
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goto pre_unlock;
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}
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/* prevent the slave from going away in sleep */
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atomic_inc(THERM_REFCNT(family_data));
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memset(rom, 0, sizeof(rom));
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while (max_trying--) {
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if (!w1_reset_select_slave(sl)) {
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unsigned int tm = 10;
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unsigned long sleep_rem;
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/* check if in parasite mode */
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w1_write_8(dev, W1_READ_PSUPPLY);
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external_power = w1_read_8(dev);
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if (w1_reset_select_slave(sl))
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continue;
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/* 10ms strong pullup/delay after the copy command */
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if (w1_strong_pullup == 2 ||
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(!external_power && w1_strong_pullup))
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w1_next_pullup(dev, tm);
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w1_write_8(dev, W1_COPY_SCRATCHPAD);
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if (external_power) {
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mutex_unlock(&dev->bus_mutex);
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sleep_rem = msleep_interruptible(tm);
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if (sleep_rem != 0) {
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ret = -EINTR;
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goto post_unlock;
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}
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ret = mutex_lock_interruptible(&dev->bus_mutex);
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if (ret != 0)
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goto post_unlock;
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} else if (!w1_strong_pullup) {
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sleep_rem = msleep_interruptible(tm);
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if (sleep_rem != 0) {
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ret = -EINTR;
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goto pre_unlock;
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}
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}
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break;
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}
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}
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pre_unlock:
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mutex_unlock(&dev->bus_mutex);
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post_unlock:
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atomic_dec(THERM_REFCNT(family_data));
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return ret;
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}
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/* DS18S20 does not feature configuration register */
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static inline int w1_DS18S20_precision(struct device *device, int val)
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{
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return 0;
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}
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static inline int w1_DS18B20_precision(struct device *device, int val)
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{
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struct w1_slave *sl = dev_to_w1_slave(device);
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struct w1_master *dev = sl->master;
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u8 rom[9], crc;
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int ret, max_trying = 10;
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u8 *family_data = sl->family_data;
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uint8_t precision_bits;
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uint8_t mask = 0x60;
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if(val > 12 || val < 9) {
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pr_warn("Unsupported precision\n");
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return -1;
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}
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ret = mutex_lock_interruptible(&dev->bus_mutex);
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if (ret != 0)
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goto post_unlock;
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if (!sl->family_data) {
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ret = -ENODEV;
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goto pre_unlock;
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}
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/* prevent the slave from going away in sleep */
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atomic_inc(THERM_REFCNT(family_data));
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memset(rom, 0, sizeof(rom));
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/* translate precision to bitmask (see datasheet page 9) */
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switch (val) {
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case 9:
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precision_bits = 0x00;
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break;
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case 10:
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precision_bits = 0x20;
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break;
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case 11:
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precision_bits = 0x40;
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break;
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case 12:
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default:
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precision_bits = 0x60;
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break;
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}
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while (max_trying--) {
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crc = 0;
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if (!w1_reset_select_slave(sl)) {
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int count = 0;
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/* read values to only alter precision bits */
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w1_write_8(dev, W1_READ_SCRATCHPAD);
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if ((count = w1_read_block(dev, rom, 9)) != 9)
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dev_warn(device, "w1_read_block() returned %u instead of 9.\n", count);
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crc = w1_calc_crc8(rom, 8);
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if (rom[8] == crc) {
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rom[4] = (rom[4] & ~mask) | (precision_bits & mask);
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if (!w1_reset_select_slave(sl)) {
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w1_write_8(dev, W1_WRITE_SCRATCHPAD);
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w1_write_8(dev, rom[2]);
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w1_write_8(dev, rom[3]);
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w1_write_8(dev, rom[4]);
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break;
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}
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}
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}
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}
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pre_unlock:
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mutex_unlock(&dev->bus_mutex);
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post_unlock:
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atomic_dec(THERM_REFCNT(family_data));
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return ret;
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}
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static inline int w1_DS18B20_convert_temp(u8 rom[9])
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{
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s16 t = le16_to_cpup((__le16 *)rom);
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@ -220,6 +400,30 @@ static inline int w1_convert_temp(u8 rom[9], u8 fid)
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return 0;
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}
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static ssize_t w1_slave_store(struct device *device,
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struct device_attribute *attr, const char *buf,
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size_t size)
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{
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int val, ret;
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struct w1_slave *sl = dev_to_w1_slave(device);
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int i;
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ret = kstrtoint(buf, 0, &val);
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if (ret)
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return ret;
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for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
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if (w1_therm_families[i].f->fid == sl->family->fid) {
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/* zero value indicates to write current configuration to eeprom */
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if (0 == val)
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ret = w1_therm_families[i].eeprom(device);
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else
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ret = w1_therm_families[i].precision(device, val);
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break;
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}
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}
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return ret ? : size;
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}
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static ssize_t w1_slave_show(struct device *device,
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struct device_attribute *attr, char *buf)
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@ -311,7 +515,7 @@ static ssize_t w1_slave_show(struct device *device,
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for (i = 0; i < 9; ++i)
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c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", rom[i]);
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c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
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crc, (verdict) ? "YES" : "NO");
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crc, (verdict) ? "YES" : "NO");
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if (verdict)
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memcpy(family_data, rom, sizeof(rom));
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else
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@ -58,6 +58,8 @@ struct w1_reg_num
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#define W1_ALARM_SEARCH 0xEC
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#define W1_CONVERT_TEMP 0x44
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#define W1_SKIP_ROM 0xCC
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#define W1_COPY_SCRATCHPAD 0x48
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#define W1_WRITE_SCRATCHPAD 0x4E
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#define W1_READ_SCRATCHPAD 0xBE
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#define W1_READ_ROM 0x33
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#define W1_READ_PSUPPLY 0xB4
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