Calibrating the PVT sensor
The Juno SoC provides a Power, Voltage and Temperature sensor that powers down the chip when it exceeds the maximum operating temperature. It also selectively powers down parts of the chip when it exceeds the temperature budget.
If you use Intelligent Power Aware Software scheduling in the Linux kernel, you must calibrate the PVT sensor.
Use the RECAL command in the Command-Line interface to calibrate the PVT sensor. Before calibrating the PVT sensor you must:
- Ensure that all firmware images are at least version MCC v119.
- Allow the board to reach ambient temperature by powering it down for at least 60 minutes.
The RECAL command returns an estimate of ambient temperature that you can accept or overwrite. Arm recommends that you provide your own value, in degrees Celsius (°C).
The following text is an example UART log of a PVT calibration:
Cmd>RECAL .... WARNING: SoC PVT recalibration has been requested. This will permanently overwrite the current SoC calibration settings. The board must have been unplugged for at least 60 minutes before starting this recalibration. Do you wish to continue(Y/N)?y Waiting for MCC to stabilise... Room temperature measured by MCC: 23.5 deg C Do you wish to use this room temperature (Y/N)?n ... Please enter room temperature in deg C (15.0 to 30.0):23.6 .... SoC PVT recalibration (23.6 deg C) Reading PVT sensors Current calibration:16E4:1E6A:2584:1F29:2643:1EFC:2616 Updated calibration:1707:1E6C:2586:1F24:263E:1EF8:2612 SoC PVT recalibration complete