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w1: w1_therm: Add support for Maxim MAX31850 thermoelement IF.

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MAX31850 shares family number 0x3B with DS1825. The device is generally
compatible with DS1825 but needs a different temperature readout.
It operates always in 14 bit mode and has all 4 higher bits of the
Config register set to 1. Conversion time is 100ms.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Link: https://lore.kernel.org/r/20220306145817.8753-1-m.reichl@fivetechno.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Markus Reichl 2022-03-06 15:58:08 +01:00 committed by Greg Kroah-Hartman
parent 6caf745d61
commit 6e07a33f97
1 changed files with 68 additions and 2 deletions
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70
drivers/w1/slaves/w1_therm.c
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@ -574,6 +574,41 @@ static inline int w1_DS18S20_convert_time(struct w1_slave *sl)
return SLAVE_CONV_TIME_OVERRIDE(sl);
}
static inline int w1_DS1825_convert_time(struct w1_slave *sl)
{
int ret;
if (!sl->family_data)
return -ENODEV; /* device unknown */
if (SLAVE_CONV_TIME_OVERRIDE(sl) != CONV_TIME_DEFAULT)
return SLAVE_CONV_TIME_OVERRIDE(sl);
/* Return the conversion time, depending on resolution,
* select maximum conversion time among all compatible devices
*/
switch (SLAVE_RESOLUTION(sl)) {
case 9:
ret = 95;
break;
case 10:
ret = 190;
break;
case 11:
ret = 375;
break;
case 12:
ret = 750;
break;
case 14:
ret = 100; /* MAX31850 only. Datasheet says 100ms */
break;
default:
ret = 750;
}
return ret;
}
static inline int w1_DS18B20_write_data(struct w1_slave *sl,
const u8 *data)
{
@ -594,6 +629,7 @@ static inline int w1_DS18B20_set_resolution(struct w1_slave *sl, int val)
/* DS18B20 resolution is 9 to 12 bits */
/* GX20MH01 resolution is 9 to 14 bits */
/* MAX31850 resolution is fixed 14 bits */
if (val < W1_THERM_RESOLUTION_MIN || val > W1_THERM_RESOLUTION_MAX)
return -EINVAL;
@ -649,6 +685,7 @@ static inline int w1_DS18B20_get_resolution(struct w1_slave *sl)
+ W1_THERM_RESOLUTION_MIN;
/* GX20MH01 has one special case:
* >=14 means 14 bits when getting resolution from bit value.
* MAX31850 delivers fixed 15 and has 14 bits.
* Other devices have no more then 12 bits.
*/
if (resolution > W1_THERM_RESOLUTION_MAX)
@ -715,6 +752,34 @@ static inline int w1_DS18S20_convert_temp(u8 rom[9])
return t;
}
/**
* w1_DS1825_convert_temp() - temperature computation for DS1825
* @rom: data read from device RAM (8 data bytes + 1 CRC byte)
*
* Can be called for any DS1825 compliant device.
* Is used by MAX31850, too
*
* Return: value in millidegrees Celsius.
*/
static inline int w1_DS1825_convert_temp(u8 rom[9])
{
u16 bv;
s16 t;
/* Signed 16-bit value to unsigned, cpu order */
bv = le16_to_cpup((__le16 *)rom);
/* Config register bit 7 = 1 - MA31850 found, 14 bit resolution */
if (rom[4] & 0x80) {
/* Mask out bits 0 (Fault) and 1 (Reserved) */
/* Avoid arithmetic shift of signed value */
bv = (bv & 0xFFFC); /* Degrees, lowest 4 bits are 2^-1, 2^-2 and 2 zero bits */
}
t = (s16)bv; /* Degrees, lowest bit is 2^-4 */
return (int)t * 1000 / 16; /* Sign-extend to int; millidegrees */
}
/* Device capability description */
/* GX20MH01 device shares family number and structure with DS18B20 */
@ -757,9 +822,10 @@ static struct w1_therm_family_converter w1_therm_families[] = {
.bulk_read = false
},
{
/* Also used for MAX31850 */
.f = &w1_therm_family_DS1825,
.convert = w1_DS18B20_convert_temp,
.get_conversion_time = w1_DS18B20_convert_time,
.convert = w1_DS1825_convert_temp,
.get_conversion_time = w1_DS1825_convert_time,
.set_resolution = w1_DS18B20_set_resolution,
.get_resolution = w1_DS18B20_get_resolution,
.write_data = w1_DS18B20_write_data,