Author: Chris Cain
Other contributors: Martha Broyles
Created: 12/03/2020
Power management on POWER platforms needs assistance from the BMC for managing the system power mode and idle power save modes. We need the ability to set and query the system power mode and also the ability to control and set idle power save parameters. This design is only applicable to POWER processors.
Each POWER processor contains an embedded PowerPC 405 processor that is referred to as the On Chip Controller or OCC. The OCC provides real time power and thermal monitoring and control. When a system is powered on, the OCCs will go to an Active state. Anytime the OCC state changes to active, the BMC will need to send a mode change and idle power saver (IPS) settings to the OCC. It will also need to send the commands if the user changes the mode or idle power save parameters.
When a system is booted, the OCC will move to an ACTIVE state. In the ACTIVE state, the OCC is managing the processor frequency, power consumption, and monitoring the systems thermal sensors. For certain error conditions it may be necessary to reset the OCC. When this happens, the OCC will move out of ACTIVE state. After recovery, the OCC will be put back into the ACTIVE state. Anytime the OCC state changes to ACTIVE or the customer updates these new parameters at runtime, the BMC will need to send the mode and the idle power saver settings to the OCC.
PowerMode was added to version 2021.1 Redfish Schema Supplement: https://www.dmtf.org/sites/default/files/standards/documents/DSP0268_2021.1.pdf
Current Customer Settable System Power Modes that will be sent to the OCCs:
A proposal for adding Idle Power Saving parameters was submitted to the Redfish committee and will be used if/when approved.
Customer Settable Idle Power Save Parameters:
Defaults will need to be configurable by the system owner (via JSON file)
The new code would be part of the openpower-occ-control repository. New code will be triggered by the following:
Code will need to trigger off of OCC state changes. The kernel currently sends a POLL command to the OCC periodically (every second). The OCC state is available in the OCC poll response data.
When initiated, the new code will send a SET_MODE_AND_STATE command (0x20) to the OCC and a SET_CONFIG_DATA (0x21) command with the Idle Power Saver parameters. These commands are defined in the OCC Interface Spec: https://github.com/open-power/docs/blob/master/occ/OCC_P9_FW_Interfaces.pdf
Default values will also be defined for Power Mode and Idle Power Saver parameters for the system. If the customer has not yet set any of these parameters, these default values will be used. If/when the customer does set any of these, that new customer parameter will become current and the default value will no longer be used.
The customer requested PowerMode and Idle Power Saver parameters will be stored as D-Bus object in the phosphor-dbus-interfaces repository: xyz/openbmc_project/Control/Power/Mode.interface.yaml Once set, these values will be retained across power cycles, AC loss, code updates, etc.
New interfaces that were described in the requirements section will be implemented. Parameters should be able to be set via user interface or via Redfish. API impact - Add Redfish support for new parameters as well as new user interface to allow customer to set power mode and idle power saver settings Security impact - update of these parameters should be able to be restricted to specific users/groups (may not want any user updating these parameters) Documentation impact - need to document new parameters Performance impact - minimal, new code will only execute on OCC state change which should normally happen once at boot time or when user changes parameters. The new code is only sending 2 additional commands which should complete within a few seconds. Developer impact - code to be written by OCC team with guidance from OpenBMC power management team Upgradability impact - None
This will be able to be tested by directly updating the power mode and idle power saver setting. This testing will be automated