Chassis power on/off targets

[Andrew Geissler]

For this sprints story, https://github.com/openbmc/openbmc/issues/951,
I need to refactor our systemd targets a bit to ensure we’ve got all
the required checkpoints the code requires.  For a bit of background
on systemd and it’s units, targets, and services,
https://www.freedesktop.org/software/systemd/man/systemd.unit.html# is
a good launching point.

Within openbmc we have the concept of targets that have associated
services with them (see /lib/systemd/system/*.wants on a system for
the full list) and we have targets that are used to control the
ordering of execution of those services in the .wants targets.

For example, to power on a system we ask systemd to run
obmc-chassis-start.target.  When you look at the filesystem you see
this (with my notes added):

ls -al obmc-chassis-start\@0.target.wants

    op-wait-power-on at 0.service -> ../op-wait-power-on at .service
        # Calls pgood_wait on /org/openbmc/control/power%i on
        o Run before obmc-power-on, obmc-power-start,

    op-power-start at 0.service -> ../op-power-start at .service
              # Calls org.openbmc.control.Power setPowerState 1
        o Run after obmc-power-start-pre, obmc-fan-control before
obmc-power-start

    op-inventory-upload at 0.service -> ../op-inventory-upload at .service
       # Calls inventory_upload.py, writes a PNOR partition
        o Run before obmc-host-starte-pre

    pcie-slot-detect at 0.service -> ../pcie-slot-detect at .service
               # Run pcie_slot_present.exe
        o Run after obmc-power-on

    obmc-start-host at 0.service -> ../op-start-host at .service
               # Calls "org.openbmc.control.Host boot”
        o Run after obmc-power-on, obmc-host-start-pre, before
obmc-host-start, obmc-host-started

    obmc-start-watchdog at 0.service -> ../obmc-start-watchdog at .service
  # Calls org.openbmc.Watchdog to set then start the watchdog
        o Run after obmc-host-started

Within these services you have lots of Before/After references to
other targets, like these to control the ordering of the service
execution:

obmc-power-start-pre
obmc-fan-control
obmc-power-start (this is a .wants, with 2 services associated with it)
obmc-power-on
obmc-host-start-pre
obmc-host-start
obmc-host-started

For my state purposes, I need to be able to do this:

Just power on and off the chassis (i.e. obmc-power-on/off) (for
debug/cronus/fsi i2c vpd programming purposes)
Know when the host has started, and when it has stopped (can use
existing targets for this)

Currently we have the chassis power and host power tied together in
obmc-chassis-start, my proposal is to simply make the obmc-power-on
and obmc-power-off targets that now have services associated with
them.  Specifically the services required to power on and off (and
verify they went on and off) the chassis.  So I’ll do this:
- move op-wait-power-on at .service and op-power-start at .service into the
obmc-power-on.wants target
- move op-power-stop at .service and op-wait-power-off at .service into the
obmc-power-off.wants target.

Thoughts or comments?
Andrew