Documentation: hwmon: Add OCC documentation
Document the hwmon interface for the OCC. Signed-off-by: Eddie James <eajames@linux.ibm.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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Eddie James
Guenter Roeck
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Kernel driver occ-hwmon
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=======================
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Supported chips:
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* POWER8
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* POWER9
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Author: Eddie James <eajames@linux.ibm.com>
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Description
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-----------
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This driver supports hardware monitoring for the On-Chip Controller (OCC)
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embedded on POWER processors. The OCC is a device that collects and aggregates
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sensor data from the processor and the system. The OCC can provide the raw
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sensor data as well as perform thermal and power management on the system.
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The P8 version of this driver is a client driver of I2C. It may be probed
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manually if an "ibm,p8-occ-hwmon" compatible device is found under the
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appropriate I2C bus node in the device-tree.
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The P9 version of this driver is a client driver of the FSI-based OCC driver.
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It will be probed automatically by the FSI-based OCC driver.
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Sysfs entries
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-------------
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The following attributes are supported. All attributes are read-only unless
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specified.
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The OCC sensor ID is an integer that represents the unique identifier of the
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sensor with respect to the OCC. For example, a temperature sensor for the third
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DIMM slot in the system may have a sensor ID of 7. This mapping is unavailable
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to the device driver, which must therefore export the sensor ID as-is.
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Some entries are only present with certain OCC sensor versions or only on
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certain OCCs in the system. The version number is not exported to the user
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but can be inferred.
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temp[1-n]_label OCC sensor ID.
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[with temperature sensor version 1]
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temp[1-n]_input Measured temperature of the component in millidegrees
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Celsius.
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[with temperature sensor version >= 2]
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temp[1-n]_type The FRU (Field Replaceable Unit) type
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(represented by an integer) for the component
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that this sensor measures.
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temp[1-n]_fault Temperature sensor fault boolean; 1 to indicate
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that a fault is present or 0 to indicate that
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no fault is present.
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[with type == 3 (FRU type is VRM)]
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temp[1-n]_alarm VRM temperature alarm boolean; 1 to indicate
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alarm, 0 to indicate no alarm
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[else]
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temp[1-n]_input Measured temperature of the component in
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millidegrees Celsius.
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freq[1-n]_label OCC sensor ID.
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freq[1-n]_input Measured frequency of the component in MHz.
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power[1-n]_input Latest measured power reading of the component in
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microwatts.
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power[1-n]_average Average power of the component in microwatts.
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power[1-n]_average_interval The amount of time over which the power average
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was taken in microseconds.
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[with power sensor version < 2]
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power[1-n]_label OCC sensor ID.
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[with power sensor version >= 2]
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power[1-n]_label OCC sensor ID + function ID + channel in the form
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of a string, delimited by underscores, i.e. "0_15_1".
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Both the function ID and channel are integers that
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further identify the power sensor.
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[with power sensor version 0xa0]
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power[1-n]_label OCC sensor ID + sensor type in the form of a string,
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delimited by an underscore, i.e. "0_system". Sensor
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type will be one of "system", "proc", "vdd" or "vdn".
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For this sensor version, OCC sensor ID will be the same
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for all power sensors.
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[present only on "master" OCC; represents the whole system power; only one of
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this type of power sensor will be present]
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power[1-n]_label "system"
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power[1-n]_input Latest system output power in microwatts.
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power[1-n]_cap Current system power cap in microwatts.
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power[1-n]_cap_not_redundant System power cap in microwatts when
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there is not redundant power.
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power[1-n]_cap_max Maximum power cap that the OCC can enforce in
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microwatts.
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power[1-n]_cap_min Minimum power cap that the OCC can enforce in
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microwatts.
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power[1-n]_cap_user The power cap set by the user, in microwatts.
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This attribute will return 0 if no user power
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cap has been set. This attribute is read-write,
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but writing any precision below watts will be
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ignored, i.e. requesting a power cap of
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500900000 microwatts will result in a power cap
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request of 500 watts.
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[with caps sensor version > 1]
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power[1-n]_cap_user_source Indicates how the user power cap was
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set. This is an integer that maps to
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system or firmware components that can
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set the user power cap.
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The following "extn" sensors are exported as a way for the OCC to provide data
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that doesn't fit anywhere else. The meaning of these sensors is entirely
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dependent on their data, and cannot be statically defined.
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extn[1-n]_label ASCII ID or OCC sensor ID.
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extn[1-n]_flags This is one byte hexadecimal value. Bit 7 indicates the
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type of the label attribute; 1 for sensor ID, 0 for
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ASCII ID. Other bits are reserved.
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extn[1-n]_input 6 bytes of hexadecimal data, with a meaning defined by
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the sensor ID.
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