summaryrefslogtreecommitdiff
path: root/drivers/w1/slaves
diff options
context:
space:
mode:
authorMarkus Reichl <m.reichl@fivetechno.de>2022-03-06 15:58:08 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-03-18 14:07:09 +0100
commit6e07a33f97d618afda456610e2633256bb2e8f04 (patch)
tree2111b4b20f0a76b89d25a867089c7490b6bddd67 /drivers/w1/slaves
parent6caf745d6172dc187d87438d753e187b0b68fed3 (diff)
w1: w1_therm: Add support for Maxim MAX31850 thermoelement IF.
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>
Diffstat (limited to 'drivers/w1/slaves')
-rw-r--r--drivers/w1/slaves/w1_therm.c70
1 files changed, 68 insertions, 2 deletions
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index c7b8a8e787e2..067692626cf0 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -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,