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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-06 19:56:51 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-06 19:56:51 -0700 |
commit | 7aefd944f038c7469571adb37769cb6f3924ecfa (patch) | |
tree | f0a8dc23633b6bbbc4f0bff932f332e847fb6c1b /Documentation/hwmon/ds1621.rst | |
parent | Merge branch 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (diff) | |
parent | hwmon: (lm75) Add support for TMP75B (diff) | |
download | linux-dev-7aefd944f038c7469571adb37769cb6f3924ecfa.tar.xz linux-dev-7aefd944f038c7469571adb37769cb6f3924ecfa.zip |
Merge tag 'hwmon-for-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging
Pull hwmon updates from Guenter Roeck:
- Add driver for Intersil ISL68137 PWM Controller
- Add driver for Lochnagar 2
- Add driver for Infineon IR38064 Voltage Regulator
- Add support for TMP75B to lm75 driver
- Convert documentation to ReST format
- Use request_muxed_region for Super-IO accesses in several drivers
- Add 'samples' attribute to ABI, and start using it
- Add support for custom sysfs attributes to pmbus drivers (used in
ISL68137 driver)
- Introduce HWMON_CHANNEL_INFO macro
- Automated changes:
- Use permission specific [SENSOR_][DEVICE_]ATTR variants
- Fix build warnings due to unused of_device_id structures
- Use HWMON_CHANNEL_INFO macro
- Various minor improvements and fixes
* tag 'hwmon-for-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging: (125 commits)
hwmon: (lm75) Add support for TMP75B
dt-bindings: hwmon: Add tmp75b to lm75.txt
hwmon: (s3c) Use dev_get_drvdata()
hwmon: (max6650) Drop call to thermal_cdev_update
docs: hwmon: remove the extension from .rst files
docs: hwmon: convert three docs to ReST format
hwmon: (max6650) add thermal cooling device capability
hwmon: (ina3221) Add voltage conversion time settings
hwmon: (ina3221) Do not read-back to cache reg_config
docs: hwmon: Add an index file and rename docs to *.rst
docs: hwmon: convert remaining files to ReST format
docs: hwmon: misc files: convert to ReST format
docs: hwmon: pmbus files: convert to ReST format
docs: hwmon: k8temp, w83793: convert to ReST format
docs: hwmon: da9052, da9055: convert to ReST format
docs: hwmon: wm831x, wm8350: convert to ReST format
docs: hwmon: dme1737, vt1211: convert to ReST format
docs: hwmon: ads1015: convert to ReST format
docs: hwmon: asc7621: convert to ReST format
docs: hwmon: ibmpowernv: convert to ReST format
...
Diffstat (limited to 'Documentation/hwmon/ds1621.rst')
-rw-r--r-- | Documentation/hwmon/ds1621.rst | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/Documentation/hwmon/ds1621.rst b/Documentation/hwmon/ds1621.rst new file mode 100644 index 000000000000..552b37e9dd34 --- /dev/null +++ b/Documentation/hwmon/ds1621.rst @@ -0,0 +1,217 @@ +Kernel driver ds1621 +==================== + +Supported chips: + + * Dallas Semiconductor / Maxim Integrated DS1621 + + Prefix: 'ds1621' + + Addresses scanned: none + + Datasheet: Publicly available from www.maximintegrated.com + + * Dallas Semiconductor DS1625 + + Prefix: 'ds1625' + + Addresses scanned: none + + Datasheet: Publicly available from www.datasheetarchive.com + + * Maxim Integrated DS1631 + + Prefix: 'ds1631' + + Addresses scanned: none + + Datasheet: Publicly available from www.maximintegrated.com + + * Maxim Integrated DS1721 + + Prefix: 'ds1721' + + Addresses scanned: none + + Datasheet: Publicly available from www.maximintegrated.com + + * Maxim Integrated DS1731 + + Prefix: 'ds1731' + + Addresses scanned: none + + Datasheet: Publicly available from www.maximintegrated.com + +Authors: + - Christian W. Zuckschwerdt <zany@triq.net> + - valuable contributions by Jan M. Sendler <sendler@sendler.de> + - ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net> + with the help of Jean Delvare <jdelvare@suse.de> + +Module Parameters +------------------ + +* polarity int + Output's polarity: + + * 0 = active high, + * 1 = active low + +Description +----------- + +The DS1621 is a (one instance) digital thermometer and thermostat. It has +both high and low temperature limits which can be user defined (i.e. +programmed into non-volatile on-chip registers). Temperature range is -55 +degree Celsius to +125 in 0.5 increments. You may convert this into a +Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity +parameter is not provided, original value is used. + +As for the thermostat, behavior can also be programmed using the polarity +toggle. On the one hand ("heater"), the thermostat output of the chip, +Tout, will trigger when the low limit temperature is met or underrun and +stays high until the high limit is met or exceeded. On the other hand +("cooler"), vice versa. That way "heater" equals "active low", whereas +"conditioner" equals "active high". Please note that the DS1621 data sheet +is somewhat misleading in this point since setting the polarity bit does +not simply invert Tout. + +A second thing is that, during extensive testing, Tout showed a tolerance +of up to +/- 0.5 degrees even when compared against precise temperature +readings. Be sure to have a high vs. low temperature limit gap of al least +1.0 degree Celsius to avoid Tout "bouncing", though! + +The alarm bits are set when the high or low limits are met or exceeded and +are reset by the module as soon as the respective temperature ranges are +left. + +The alarm registers are in no way suitable to find out about the actual +status of Tout. They will only tell you about its history, whether or not +any of the limits have ever been met or exceeded since last power-up or +reset. Be aware: When testing, it showed that the status of Tout can change +with neither of the alarms set. + +Since there is no version or vendor identification register, there is +no unique identification for these devices. Therefore, explicit device +instantiation is required for correct device identification and functionality +(one device per address in this address range: 0x48..0x4f). + +The DS1625 is pin compatible and functionally equivalent with the DS1621, +but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are +also pin compatible with the DS1621 and provide multi-resolution support. + +Additionally, the DS1721 data sheet says the temperature flags (THF and TLF) +are used internally, however, these flags do get set and cleared as the actual +temperature crosses the min or max settings (which by default are set to 75 +and 80 degrees respectively). + +Temperature Conversion +---------------------- + +- DS1621 - 750ms (older devices may take up to 1000ms) +- DS1625 - 500ms +- DS1631 - 93ms..750ms for 9..12 bits resolution, respectively. +- DS1721 - 93ms..750ms for 9..12 bits resolution, respectively. +- DS1731 - 93ms..750ms for 9..12 bits resolution, respectively. + +Note: +On the DS1621, internal access to non-volatile registers may last for 10ms +or less (unverified on the other devices). + +Temperature Accuracy +-------------------- + +- DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees) +- DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees) +- DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees) +- DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees) +- DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees) + +.. Note:: + + Please refer to the device datasheets for accuracy at other temperatures. + +Temperature Resolution: +----------------------- +As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution +support, which is achieved via the R0 and R1 config register bits, where: + +R0..R1 +------ + +== == =============================== +R0 R1 +== == =============================== + 0 0 9 bits, 0.5 degrees Celsius + 1 0 10 bits, 0.25 degrees Celsius + 0 1 11 bits, 0.125 degrees Celsius + 1 1 12 bits, 0.0625 degrees Celsius +== == =============================== + +.. Note:: + + At initial device power-on, the default resolution is set to 12-bits. + +The resolution mode for the DS1631, DS1721, or DS1731 can be changed from +userspace, via the device 'update_interval' sysfs attribute. This attribute +will normalize the range of input values to the device maximum resolution +values defined in the datasheet as follows: + +============= ================== =============== +Resolution Conversion Time Input Range + (C/LSB) (msec) (msec) +============= ================== =============== +0.5 93.75 0....94 +0.25 187.5 95...187 +0.125 375 188..375 +0.0625 750 376..infinity +============= ================== =============== + +The following examples show how the 'update_interval' attribute can be +used to change the conversion time:: + + $ cat update_interval + 750 + $ cat temp1_input + 22062 + $ + $ echo 300 > update_interval + $ cat update_interval + 375 + $ cat temp1_input + 22125 + $ + $ echo 150 > update_interval + $ cat update_interval + 188 + $ cat temp1_input + 22250 + $ + $ echo 1 > update_interval + $ cat update_interval + 94 + $ cat temp1_input + 22000 + $ + $ echo 1000 > update_interval + $ cat update_interval + 750 + $ cat temp1_input + 22062 + $ + +As shown, the ds1621 driver automatically adjusts the 'update_interval' +user input, via a step function. Reading back the 'update_interval' value +after a write operation provides the conversion time used by the device. + +Mathematically, the resolution can be derived from the conversion time +via the following function: + + g(x) = 0.5 * [minimum_conversion_time/x] + +where: + + - 'x' = the output from 'update_interval' + - 'g(x)' = the resolution in degrees C per LSB. + - 93.75ms = minimum conversion time |