The system can be powered on by several methods, such as the obmcutil tool, a Redfish command, or a power button on the system enclosure.
Whichever method is used, it sets the state property to 1 on the org.openbmc.control.Power D-Bus interface. The D-Bus object path is /org/openbmc/control/power0, which represents the entire system. See Chassis Status for more information.
The phosphor-power-sequencer application only supports powering on the entire system. In a multiple chassis system, phosphor-power-sequencer does not support powering on individual chassis independent of the rest of the system.
In a single chassis system, phosphor-power-sequencer will always attempt to power on the chassis.
In a multiple chassis system, phosphor-power-sequencer will only attempt to power on chassis with the proper status:
Present property is trueEnabled property is true (if interface exists)Available property is true (if interface exists)Status property is Good (if interface exists)phosphor-power-sequencer will set the state property to 1 for each chassis that is being powered on. It will set state to 0 for each chassis not being powered on.
If no chassis are in the proper status to power on, phosphor-power-sequencer will log an error. phosphor-chassis-state-manager will power off the system.
See Chassis Status for more information on these properties.
phosphor-power-sequencer powers on the main (non-standby) voltage rails in a chassis by toggling a named GPIO to the power sequencer device in the chassis. For more information, see Named GPIOs.
In each chassis being powered on, the power sequencer device powers on the individual voltage rails in the correct order.
When all voltage rails have been successfully powered on in a chassis, the power sequencer device will set the chassis power good (pgood) signal to true.
phosphor-power-sequencer reads the chassis pgood signal from a named GPIO. For more information, see Monitoring Chassis Power Good.
When the chassis power good signal changes to true, phosphor-power-sequencer will set the pgood property to 1 on the org.openbmc.control.Power interface for the chassis object path. The power on has finished for that chassis.
When all chassis that were being powered on have finished, phosphor-power-sequencer will set the pgood property to 1 on the org.openbmc.control.Power interface for the system object path.
See Chassis Status for more information on the pgood property.
After all chassis have powered on, the rest of the boot process continues. The host operating system will eventually be started.
When the power sequencer device is powering on the main voltage rails, one of the rails may fail to power on. Similarly, after the system has powered on, one of the voltage rails that had been providing power to the chassis might suddenly power off.
In both cases the result is a pgood fault. See Power Good Faults for information on how the error is handled.
phosphor-power-sequencer may become unable to read the chassis power good signal from the named GPIO due to:
Available property of the chassis changes to false.See Monitoring Chassis Power Good for more information on how the error is handled.