>In this
>doc: https://github.com/openbmc/docs/blob/master/architecture/openbmc<= /a>
>-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 t= hat path, the above dependencies are not there.
>There is only a depe= ndency on phosphor-fan-presence-tach@0.service
>
>There is= some state service that lead to things with xzy paths, and I
>eventu= ally 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 sys= fs so that these nodes are not
>traditional files?
>
>Wha= t I am trying to understand is two things:
>
>- Interaction wit= h the power regulator
>- Interaction with the host cpu
>
>= ;So my hope is someone can connect the dots of the path from the dbus
&g= t;to systemd through the targets to a service executable doing the work
= >so I can try to replace them with:
>
>- Something that turn= s the regulators on/off, with pmbus in this
>case.
>- Something= that can behave like a host to keep the system happy like
>a real sy= stem.

Hi.&nb= sp; There is some design documentation here

https://github.com/openbmc/d= ocs/blob/master/designs/state-management-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.<= /div>

The op-power-start are for systems = following the OpenPOWER reference

designs. The regulat= ors are sequenced by an external microcontroller

based on th= e state of a POWER=5FON 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).

<= /div>

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

pinged and stopped via IPMI.

<= br>

If you are prototyping for a x86 system, there are alternativ= e

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 the= y 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<= br>>
>https://github.com/Proclivis/meta-pmbus-raspber= rypi.git
>https://github.com/Proclivis/meta-pmbus-phosp= hor.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.s= ystemd1.Manager; member=3DStartUnit
>   string "obmc-host-start@0.targ= et"
>   string "replace"
>method call time=3D1598= 039669.276170 sender=3D:1.3 ->
>destination=3Dorg.freedesktop.DBus= serial=3D775
>path=3D/org/freedesktop/DBus; interface=3Dorg.freedesk= top.DBus;
>member=3DGetConnectionUnixUser
>   string = ":1.48"
>method return time=3D1598039669.276234 sender=3Dorg.freedesk= top.DBus ->
>destination=3D:1.3 serial=3D4294967295 reply=5Fserial= =3D775
>   uint32 0
>method call time=3D1598039669.28= 0376 sender=3D:1.3 ->
>destination=3Dorg.freedesktop.DBus serial= =3D776
>path=3D/org/freedesktop/DBus; interface=3Dorg.freedesktop.DBu= s;
>member=3DAddMatch
>   string
>"type=3D'sign= al',sender=3D'org.freedesktop.DBus',path=3D'/org/freedesktop/D
>Bus',= interface=3D'org.freedesktop.DBus',member=3D'NameOwnerChanged',arg0=3D
&= gt;':1.48'"
>method return time=3D1598039669.280661 sender=3Dorg.free= desktop.DBus ->
>destination=3D:1.3 serial=3D4294967295 reply=5Fse= rial=3D776
>method call time=3D1598039669.280701 sender=3D:1.3 -><= br>>destination=3Dorg.freedesktop.DBus serial=3D777
>path=3D/org/f= reedesktop/DBus; interface=3Dorg.freedesktop.DBus;
>member=3DGetNameO= wner
>   string ":1.48"
>method return time=3D1598039= 669.280738 sender=3Dorg.freedesktop.DBus ->
>destination=3D:1.3 se= rial=3D4294967295 reply=5Fserial=3D777
>   string ":1.48">signal time=3D1598039669.280774 sender=3D:1.3 -> destination=3D(nu= ll
>destination) serial=3D778 path=3D/org/freedesktop/systemd1;
&g= t;interface=3Dorg.freedesktop.systemd1.Manager; member=3DUnitNew
>&nb= sp; string "obmc-host-start@0.target"
>   object path
>= ;"/org/freedesktop/systemd1/unit/obmc=5F2dhost=5F2dstart=5F400=5F2etarget"<= br>>signal time=3D1598039669.280823 sender=3D:1.3 -> destination=3D(n= ull
>destination) serial=3D779 path=3D/org/freedesktop/systemd1;
&= gt;interface=3Dorg.freedesktop.systemd1.Manager; member=3DJobNew
>&nb= sp; uint32 1105
>   object path "/org/freedesktop/sys= temd1/job/1105"
>   string "obmc-host-start@0.target"
>metho= d return time=3D1598039669.280883 sender=3D:1.3 -> destination=3D:1.48>serial=3D780 reply=5Fserial=3D33
>   object path "/or= g/freedesktop/systemd1/job/1105"
>signal time=3D1598039669.281305 sen= der=3D:1.48 -> destination=3D(null
>destination) serial=3D34 path= =3D/xyz/openbmc=5Fproject/state/host0;
>interface=3Dorg.freedesktop.D= Bus.Properties; member=3DPropertiesChanged
>   string "xyz.= openbmc=5Fproject.State.Host"
>   array [
> &nbs= p;    dict entry(
>      = ;   string "RequestedHostTransition"
>   &nb= sp;     variant      &nbs= p;      string
>"xyz.openbmc=5Fproject.State= .Host.Transition.On"
>      )
> &= nbsp; ]
>   array [
>   ]