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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 2016-05-01 23:23:33 +02:00 committed by Greg Kroah-Hartman
parent ae53e37400
commit 0a19f129d7
3 changed files with 222 additions and 8 deletions
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10
Documentation/w1/slaves/w1_therm
View File

@ -33,7 +33,15 @@ temperature conversion at a time. If none of the devices are parasite
powered it would be possible to convert all the devices at the same
time and then go back to read individual sensors. That isn't
currently supported. The driver also doesn't support reduced
precision (which would also reduce the conversion time).
precision (which would also reduce the conversion time) when reading values.
Writing a value between 9 and 12 to the sysfs w1_slave file will change the
precision of the sensor for the next readings. This value is in (volatile)
SRAM, so it is reset when the sensor gets power-cycled.
To store the current precision configuration into EEPROM, the value 0
has to be written to the sysfs w1_slave file. Since the EEPROM has a limited
amount of writes (>50k), this command should be used wisely.
The module parameter strong_pullup can be set to 0 to disable the
strong pullup, 1 to enable autodetection or 2 to force strong pullup.

218
drivers/w1/slaves/w1_therm.c
View File

@ -92,10 +92,13 @@ static void w1_therm_remove_slave(struct w1_slave *sl)
static ssize_t w1_slave_show(struct device *device,
struct device_attribute *attr, char *buf);
static ssize_t w1_slave_store(struct device *device,
struct device_attribute *attr, const char *buf, size_t size);
static ssize_t w1_seq_show(struct device *device,
struct device_attribute *attr, char *buf);
static DEVICE_ATTR_RO(w1_slave);
static DEVICE_ATTR_RW(w1_slave);
static DEVICE_ATTR_RO(w1_seq);
static struct attribute *w1_therm_attrs[] = {
@ -154,8 +157,17 @@ struct w1_therm_family_converter
u16 reserved;
struct w1_family *f;
int (*convert)(u8 rom[9]);
int (*precision)(struct device *device, int val);
int (*eeprom)(struct device *device);
};
/* write configuration to eeprom */
static inline int w1_therm_eeprom(struct device *device);
/* Set precision for conversion */
static inline int w1_DS18B20_precision(struct device *device, int val);
static inline int w1_DS18S20_precision(struct device *device, int val);
/* The return value is millidegrees Centigrade. */
static inline int w1_DS18B20_convert_temp(u8 rom[9]);
static inline int w1_DS18S20_convert_temp(u8 rom[9]);
@ -163,26 +175,194 @@ static inline int w1_DS18S20_convert_temp(u8 rom[9]);
static struct w1_therm_family_converter w1_therm_families[] = {
{
.f = &w1_therm_family_DS18S20,
.convert = w1_DS18S20_convert_temp
.convert = w1_DS18S20_convert_temp,
.precision = w1_DS18S20_precision,
.eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS1822,
.convert = w1_DS18B20_convert_temp
.convert = w1_DS18B20_convert_temp,
.precision = w1_DS18S20_precision,
.eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS18B20,
.convert = w1_DS18B20_convert_temp
.convert = w1_DS18B20_convert_temp,
.precision = w1_DS18B20_precision,
.eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS28EA00,
.convert = w1_DS18B20_convert_temp
.convert = w1_DS18B20_convert_temp,
.precision = w1_DS18S20_precision,
.eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS1825,
.convert = w1_DS18B20_convert_temp
.convert = w1_DS18B20_convert_temp,
.precision = w1_DS18S20_precision,
.eeprom = w1_therm_eeprom
}
};
static inline int w1_therm_eeprom(struct device *device)
{
struct w1_slave *sl = dev_to_w1_slave(device);
struct w1_master *dev = sl->master;
u8 rom[9], external_power;
int ret, max_trying = 10;
u8 *family_data = sl->family_data;
ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
goto post_unlock;
if (!sl->family_data) {
ret = -ENODEV;
goto pre_unlock;
}
/* prevent the slave from going away in sleep */
atomic_inc(THERM_REFCNT(family_data));
memset(rom, 0, sizeof(rom));
while (max_trying--) {
if (!w1_reset_select_slave(sl)) {
unsigned int tm = 10;
unsigned long sleep_rem;
/* check if in parasite mode */
w1_write_8(dev, W1_READ_PSUPPLY);
external_power = w1_read_8(dev);
if (w1_reset_select_slave(sl))
continue;
/* 10ms strong pullup/delay after the copy command */
if (w1_strong_pullup == 2 ||
(!external_power && w1_strong_pullup))
w1_next_pullup(dev, tm);
w1_write_8(dev, W1_COPY_SCRATCHPAD);
if (external_power) {
mutex_unlock(&dev->bus_mutex);
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -EINTR;
goto post_unlock;
}
ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
goto post_unlock;
} else if (!w1_strong_pullup) {
sleep_rem = msleep_interruptible(tm);
if (sleep_rem != 0) {
ret = -EINTR;
goto pre_unlock;
}
}
break;
}
}
pre_unlock:
mutex_unlock(&dev->bus_mutex);
post_unlock:
atomic_dec(THERM_REFCNT(family_data));
return ret;
}
/* DS18S20 does not feature configuration register */
static inline int w1_DS18S20_precision(struct device *device, int val)
{
return 0;
}
static inline int w1_DS18B20_precision(struct device *device, int val)
{
struct w1_slave *sl = dev_to_w1_slave(device);
struct w1_master *dev = sl->master;
u8 rom[9], crc;
int ret, max_trying = 10;
u8 *family_data = sl->family_data;
uint8_t precision_bits;
uint8_t mask = 0x60;
if(val > 12 || val < 9) {
pr_warn("Unsupported precision\n");
return -1;
}
ret = mutex_lock_interruptible(&dev->bus_mutex);
if (ret != 0)
goto post_unlock;
if (!sl->family_data) {
ret = -ENODEV;
goto pre_unlock;
}
/* prevent the slave from going away in sleep */
atomic_inc(THERM_REFCNT(family_data));
memset(rom, 0, sizeof(rom));
/* translate precision to bitmask (see datasheet page 9) */
switch (val) {
case 9:
precision_bits = 0x00;
break;
case 10:
precision_bits = 0x20;
break;
case 11:
precision_bits = 0x40;
break;
case 12:
default:
precision_bits = 0x60;
break;
}
while (max_trying--) {
crc = 0;
if (!w1_reset_select_slave(sl)) {
int count = 0;
/* read values to only alter precision bits */
w1_write_8(dev, W1_READ_SCRATCHPAD);
if ((count = w1_read_block(dev, rom, 9)) != 9)
dev_warn(device, "w1_read_block() returned %u instead of 9.\n", count);
crc = w1_calc_crc8(rom, 8);
if (rom[8] == crc) {
rom[4] = (rom[4] & ~mask) | (precision_bits & mask);
if (!w1_reset_select_slave(sl)) {
w1_write_8(dev, W1_WRITE_SCRATCHPAD);
w1_write_8(dev, rom[2]);
w1_write_8(dev, rom[3]);
w1_write_8(dev, rom[4]);
break;
}
}
}
}
pre_unlock:
mutex_unlock(&dev->bus_mutex);
post_unlock:
atomic_dec(THERM_REFCNT(family_data));
return ret;
}
static inline int w1_DS18B20_convert_temp(u8 rom[9])
{
s16 t = le16_to_cpup((__le16 *)rom);
@ -220,6 +400,30 @@ static inline int w1_convert_temp(u8 rom[9], u8 fid)
return 0;
}
static ssize_t w1_slave_store(struct device *device,
struct device_attribute *attr, const char *buf,
size_t size)
{
int val, ret;
struct w1_slave *sl = dev_to_w1_slave(device);
int i;
ret = kstrtoint(buf, 0, &val);
if (ret)
return ret;
for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
if (w1_therm_families[i].f->fid == sl->family->fid) {
/* zero value indicates to write current configuration to eeprom */
if (0 == val)
ret = w1_therm_families[i].eeprom(device);
else
ret = w1_therm_families[i].precision(device, val);
break;
}
}
return ret ? : size;
}
static ssize_t w1_slave_show(struct device *device,
struct device_attribute *attr, char *buf)
@ -311,7 +515,7 @@ static ssize_t w1_slave_show(struct device *device,
for (i = 0; i < 9; ++i)
c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", rom[i]);
c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
crc, (verdict) ? "YES" : "NO");
crc, (verdict) ? "YES" : "NO");
if (verdict)
memcpy(family_data, rom, sizeof(rom));
else

2
drivers/w1/w1.h
View File

@ -58,6 +58,8 @@ struct w1_reg_num
#define W1_ALARM_SEARCH 0xEC
#define W1_CONVERT_TEMP 0x44
#define W1_SKIP_ROM 0xCC
#define W1_COPY_SCRATCHPAD 0x48
#define W1_WRITE_SCRATCHPAD 0x4E
#define W1_READ_SCRATCHPAD 0xBE
#define W1_READ_ROM 0x33
#define W1_READ_PSUPPLY 0xB4