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While the chips supported by this driver do not directly support current limits, they do support setting shunt voltage limits. The shunt voltage divided by the shunt resistor value is the current. On top of that, calibration values are set such that in the shunt voltage register and the current register report the same values. That means we can report and configure current limits based on shunt voltage limits, and we can do so with much better accuracy than by setting shunt voltage limits. Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
128 lines
4.0 KiB
ReStructuredText
128 lines
4.0 KiB
ReStructuredText
Kernel driver ina2xx
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====================
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Supported chips:
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* Texas Instruments INA219
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Prefix: 'ina219'
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Addresses: I2C 0x40 - 0x4f
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Datasheet: Publicly available at the Texas Instruments website
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https://www.ti.com/
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* Texas Instruments INA220
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Prefix: 'ina220'
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Addresses: I2C 0x40 - 0x4f
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Datasheet: Publicly available at the Texas Instruments website
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https://www.ti.com/
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* Texas Instruments INA226
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Prefix: 'ina226'
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Addresses: I2C 0x40 - 0x4f
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Datasheet: Publicly available at the Texas Instruments website
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https://www.ti.com/
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* Texas Instruments INA230
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Prefix: 'ina230'
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Addresses: I2C 0x40 - 0x4f
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Datasheet: Publicly available at the Texas Instruments website
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https://www.ti.com/
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* Texas Instruments INA231
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Prefix: 'ina231'
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Addresses: I2C 0x40 - 0x4f
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Datasheet: Publicly available at the Texas Instruments website
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https://www.ti.com/
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Author: Lothar Felten <lothar.felten@gmail.com>
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Description
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-----------
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The INA219 is a high-side current shunt and power monitor with an I2C
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interface. The INA219 monitors both shunt drop and supply voltage, with
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programmable conversion times and filtering.
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The INA220 is a high or low side current shunt and power monitor with an I2C
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interface. The INA220 monitors both shunt drop and supply voltage.
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The INA226 is a current shunt and power monitor with an I2C interface.
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The INA226 monitors both a shunt voltage drop and bus supply voltage.
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INA230 and INA231 are high or low side current shunt and power monitors
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with an I2C interface. The chips monitor both a shunt voltage drop and
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bus supply voltage.
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The shunt value in micro-ohms can be set via platform data or device tree at
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compile-time or via the shunt_resistor attribute in sysfs at run-time. Please
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refer to the Documentation/devicetree/bindings/hwmon/ti,ina2xx.yaml for bindings
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if the device tree is used.
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Additionally ina226 supports update_interval attribute as described in
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Documentation/hwmon/sysfs-interface.rst. Internally the interval is the sum of
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bus and shunt voltage conversion times multiplied by the averaging rate. We
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don't touch the conversion times and only modify the number of averages. The
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lower limit of the update_interval is 2 ms, the upper limit is 2253 ms.
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The actual programmed interval may vary from the desired value.
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General sysfs entries
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---------------------
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======================= ===============================
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in0_input Shunt voltage(mV) channel
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in1_input Bus voltage(mV) channel
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curr1_input Current(mA) measurement channel
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power1_input Power(uW) measurement channel
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shunt_resistor Shunt resistance(uOhm) channel
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======================= ===============================
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Sysfs entries for ina226, ina230 and ina231 only
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------------------------------------------------
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======================= ====================================================
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curr1_lcrit Critical low current
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curr1_crit Critical high current
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curr1_lcrit_alarm Current critical low alarm
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curr1_crit_alarm Current critical high alarm
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in0_lcrit Critical low shunt voltage
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in0_crit Critical high shunt voltage
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in0_lcrit_alarm Shunt voltage critical low alarm
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in0_crit_alarm Shunt voltage critical high alarm
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in1_lcrit Critical low bus voltage
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in1_crit Critical high bus voltage
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in1_lcrit_alarm Bus voltage critical low alarm
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in1_crit_alarm Bus voltage critical high alarm
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power1_crit Critical high power
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power1_crit_alarm Power critical high alarm
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update_interval data conversion time; affects number of samples used
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to average results for shunt and bus voltages.
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======================= ====================================================
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.. note::
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- Configure `shunt_resistor` before configure `power1_crit`, because power
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value is calculated based on `shunt_resistor` set.
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- Because of the underlying register implementation, only one `*crit` setting
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and its `alarm` can be active. Writing to one `*crit` setting clears other
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`*crit` settings and alarms. Writing 0 to any `*crit` setting clears all
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`*crit` settings and alarms.
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