Mike

On Aug 23, 2020, at 9:22 PM, = Milton Miller II <miltonm@us.ibm.com> wrote:

Resend as plain text.

On = August 21, 2020, Mike Jones wrote:>I am trying to understand how
the Server power button in the webui
works.

As before, = using raspberry pi, and I=E2=80=99ll leave project links at the
end for anyone that wants to use them. Things work up to = monitoring
voltages. Note the conf project has a phosphor = branch for the full
monty.>>To reverse engineer, I = setup: dbus-monitor =E2=80=94system >
someFile.log

There is a message for = systemd1.Manager; member=3DStartUnit and best I
can tell, = somehow this gets routed to systemd to start some service
or= run some exe. I see this mentioned in the dbus transactions:

"obmc-host-start@0.target=E2=80=9D

And that is in /lib/systemd/system and depends
on= obmc-host-startmin@0.target, but that does not depend on = any
service. So that is a dead end. It also depends on a = reboot
attempts,
but I think that is not responsible for power = on/off.

Then there are chassis services, = but I cannot find a link from
obmc-host-start@0.target to objc-chassis-poweron@0.target.

In this
doc: https://github.com/openbmc/docs/blob/master/architecture/openbm=
c
-systemd.md

It shows:

ls -1 = /lib/systemd/system/obmc-chassis-poweron\@0.target.requires/
op-power-start@0.service op-wait-power-on@0.service>>But when I =E2=80=9Cls=E2= =80=9D
that path, the above dependencies are = not there.
There is = only a dependency on phosphor-fan-presence-tach@0.service

There is some state service that lead to things with xzy = paths, and
I
eventually found /run/systemd/units. These have = file names starting
with =E2=80=9Cinvocation=E2=80=9D in = the names and link to GUID like nodes that
don=E2=80=99t
=E2=80=9Ccat=E2=80=9D like a normal file. So I = am not sure how those work. Is there
some kernel driver = that works like sysfs so that these nodes are not
traditional files?

What I am = trying to understand is two things:

- = Interaction with the power regulator
- Interaction with = the host cpu

So my hope is someone can = connect the dots of the path from the dbus
to systemd = through the targets to a service executable doing the
work
so I can try to replace them with:

- Something that turns the regulators on/off, with pmbus in = this
case.
- Something that can behave like = a host to keep the system happy
like
a real system.

Hi. = There is some design documentation here

https://github.com/openbmc/docs/blob/master/designs/state-manag= ement-
and-external-interfaces.md

and that links to phosphor-state-manager which has a lot of = the units

that kick off power and state = transitions.

The = op-power-start are for systems following the OpenPOWER reference
designs. = The regulators are sequenced by an external microcontroller

based on the state of a POWER_ON gpio from the = BMC and a return
PGOOD to indicate the state. There are also other op- = prefixed units
that
initiate the = host processor initialization (after the units check
that = fans are
running as you found).

There is also a watchdog that is started when the host is = started and

pinged and stopped via IPMI.

If you are prototyping for a x86 system, there = are alternative
power implementations where the gpio toggles to represent = a
main = power button push and their start cpu sequences. I think
there are = also arm systems but don't know what they are using
for host = interaction.

I hope this advances your = investigation and learning.

milton

Mike

My repos
=E2=80=94=E2=80=94=E2=80=94=E2=80=94=E2=80= =94=E2=80=94

https://github.com/Proclivis/meta-pmbus-raspberrypi.git
https://github.com/Proclivis/meta-pmbus-phosphor.git
https://github.com/Proclivis/conf-openbmc-adi.git

The monitor messages for StartUnit
=E2=80=94=E2=80=94=E2=80=94

method= call time=3D1598039669.247458 sender=3D:1.48 ->
destination=3Dorg.freedesktop.systemd1 serial=3D33
path=3D/org/freedesktop/systemd1;
interface=3Dorg.freedesktop.systemd1.Manager; = member=3DStartUnit
string = "obmc-host-start@0.target"
string "replace"
method call time=3D1598039669.276170 sender=3D:1.3 ->
destination=3Dorg.freedesktop.DBus serial=3D775
path=3D/org/freedesktop/DBus; = interface=3Dorg.freedesktop.DBus;
member=3DGetConnectionUnixUser
string = ":1.48"
method return time=3D1598039669.276234 = sender=3Dorg.freedesktop.DBus ->
destination=3D:1.3 = serial=3D4294967295 reply_serial=3D775
uint32 0
method call time=3D1598039669.280376 sender=3D:1.3 ->
destination=3Dorg.freedesktop.DBus serial=3D776
path=3D/org/freedesktop/DBus; = interface=3Dorg.freedesktop.DBus;
member=3DAddMatch
string
"type=3D'signal',sender=3D'org.freedesktop.DBus',path=3D'/org/f= reedesktop/
D
Bus',interface=3D'org.freedesktop.DBus',member=3D'NameOwnerChan= ged',arg0
=3D
':1.48'"
method return = time=3D1598039669.280661 sender=3Dorg.freedesktop.DBus ->
destination=3D:1.3 serial=3D4294967295 reply_serial=3D776
method call time=3D1598039669.280701 sender=3D:1.3 ->
destination=3Dorg.freedesktop.DBus serial=3D777
path=3D/org/freedesktop/DBus; = interface=3Dorg.freedesktop.DBus;
member=3DGetNameOwner
string ":1.48"
method return = time=3D1598039669.280738 sender=3Dorg.freedesktop.DBus ->
destination=3D:1.3 serial=3D4294967295 reply_serial=3D777
string ":1.48"
signal = time=3D1598039669.280774 sender=3D:1.3 -> destination=3D(null
destination) serial=3D778 path=3D/org/freedesktop/systemd1;
interface=3Dorg.freedesktop.systemd1.Manager; = member=3DUnitNew
string "obmc-host-start@0.target"
object = path
"/org/freedesktop/systemd1/unit/obmc_2dhost_2dstart_400_2etarge= t"
signal time=3D1598039669.280823 sender=3D:1.3 -> = destination=3D(null
destination) serial=3D779 = path=3D/org/freedesktop/systemd1;
interface=3Dorg.freedesktop.systemd1.Manager; = member=3DJobNew
uint32 1105
object= path "/org/freedesktop/systemd1/job/1105"
string = "obmc-host-start@0.target"
method return = time=3D1598039669.280883 sender=3D:1.3 ->
destination=3D:1.48
serial=3D780 reply_serial=3D33
object path "/org/freedesktop/systemd1/job/1105"
signal time=3D1598039669.281305 sender=3D:1.48 -> = destination=3D(null
destination) serial=3D34 = path=3D/xyz/openbmc_project/state/host0;
interface=3Dorg.freedesktop.DBus.Properties; = member=3DPropertiesChanged
string = "xyz.openbmc_project.State.Host"
array [
    dict entry(
       string = "RequestedHostTransition"
       variant =             st= ring
"xyz.openbmc_project.State.Host.Transition.On"
    )
]
array [
]