Reads one sensor for a PMBus regulator rail. Communicates with the device directly using the I2C interface.
This action should be executed during sensor_monitoring for the rail.
Currently the following sensor types are supported:
| Type | Description |
|---|---|
| iout | Output current |
| iout_peak | Highest output current |
| iout_valley | Lowest output current |
| pout | Output power |
| temperature | Temperature |
| temperature_peak | Highest temperature |
| vout | Output voltage |
| vout_peak | Highest output voltage |
| vout_valley | Lowest output voltage |
Notes:
Currently the following PMBus data formats are supported:
| Format | Description |
|---|---|
| linear_11 | Linear data format used for values not related to voltage output, such as output current, input voltage, and temperature. Two byte value with an 11-bit, two's complement mantissa and a 5-bit, two's complement exponent. |
| linear_16 | Linear data format used for values related to voltage output. Two byte (16-bit), unsigned integer that is raised to the power of an exponent. The exponent is not stored within the two bytes. |
The "linear_16" data format requires an exponent value.
If the device supports the PMBus VOUT_MODE command, the exponent value can be read from the device.
If VOUT_MODE is not supported by the device, the exponent value must be specified using the "exponent" property. The exponent value can normally be found in the device documentation (data sheet).
A D-Bus sensor object will be created on the BMC to store the sensor value. This makes the sensor available to external interfaces like Redfish.
D-Bus sensors have an object path with the following format:
/xyz/openbmc_project/sensors/<namespace>/<sensor_name>
The D-Bus sensors <namespace> is the general category of the sensor. The following table shows how the sensor type is mapped to a D-Bus sensors <namespace>.
| Sensor Type | D-Bus <namespace> |
|---|---|
| iout | current |
| iout_peak | current |
| iout_valley | current |
| pout | power |
| temperature | temperature |
| temperature_peak | temperature |
| vout | voltage |
| vout_peak | voltage |
| vout_valley | voltage |
The D-Bus <sensor_name> must be unique across the entire system. It will be set to the following:
<rail_id>_<sensor_type>
For example, if sensor monitoring for rail "vdd0" reads a "vout_peak" sensor, the resulting D-Bus <sensor_name> will be "vdd0_vout_peak".
Peak and valley sensor values are calculated internally by the regulator since it can sample values very frequently and catch transient events. When these peak/valley values are read over PMBus, the regulator will often clear its internal value and start calculating a new peak/valley. To avoid losing information, the D-Bus sensor will contain the highest peak/lowest valley value that has been read since the system was powered on. When the system is powered off, the D-Bus peak/valley sensor values are cleared.
| Name | Required | Type | Description |
|---|---|---|---|
| type | yes | string | Sensor type. Specify one of the following: "iout", "iout_peak", "iout_valley", "pout", "temperature", "temperature_peak", "vout", "vout_peak", "vout_valley". |
| command | yes | string | PMBus command code expressed in hexadecimal. Must be prefixed with 0x and surrounded by double quotes. |
| format | yes | string | Data format of the sensor value returned by the device. Specify one of the following: "linear_11", "linear_16". |
| exponent | no | number | Exponent value for "linear_16" data format. Can be positive or negative. If not specified, the exponent value will be read from VOUT_MODE. |
true
{
"comments": [ "Read output current from READ_IOUT." ],
"pmbus_read_sensor": {
"type": "iout",
"command": "0x8C",
"format": "linear_11"
}
}
{
"comments": [ "Read output voltage from READ_VOUT. Specify exponent." ],
"pmbus_read_sensor": {
"type": "vout",
"command": "0x8B",
"format": "linear_16",
"exponent": -8
}
}