Server Power On mystery

[Milton Miller II]

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>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’ll 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 —system >
>someFile.log
>>
>>There is a message for systemd1.Manager; member=StartUnit 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 at 0.target”
>>
>>And that is in /lib/systemd/system and depends
>>on obmc-host-startmin at 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 at 0.target to objc-chassis-poweron at 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 at 0.service op-wait-power-on at 0.service>>But when I “ls”
>that path, the above dependencies are not there.
>>There is only a dependency on phosphor-fan-presence-tach at 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 “invocation” in the names and link to GUID like nodes that
>don’t
>>“cat” 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-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.
>
>
>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
>>——————
>>
>>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
>>———
>>
>>method call time=1598039669.247458 sender=:1.48 ->
>>destination=org.freedesktop.systemd1 serial=33
>>path=/org/freedesktop/systemd1;
>>interface=org.freedesktop.systemd1.Manager; member=StartUnit
>>   string "obmc-host-start at 0.target"
>>   string "replace"
>>method call time=1598039669.276170 sender=:1.3 ->
>>destination=org.freedesktop.DBus serial=775
>>path=/org/freedesktop/DBus; interface=org.freedesktop.DBus;
>>member=GetConnectionUnixUser
>>   string ":1.48"
>>method return time=1598039669.276234 sender=org.freedesktop.DBus ->
>>destination=:1.3 serial=4294967295 reply_serial=775
>>   uint32 0
>>method call time=1598039669.280376 sender=:1.3 ->
>>destination=org.freedesktop.DBus serial=776
>>path=/org/freedesktop/DBus; interface=org.freedesktop.DBus;
>>member=AddMatch
>>   string
>>"type='signal',sender='org.freedesktop.DBus',path='/org/freedesktop/
>D
>>Bus',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0
>=
>>':1.48'"
>>method return time=1598039669.280661 sender=org.freedesktop.DBus ->
>>destination=:1.3 serial=4294967295 reply_serial=776
>>method call time=1598039669.280701 sender=:1.3 ->
>>destination=org.freedesktop.DBus serial=777
>>path=/org/freedesktop/DBus; interface=org.freedesktop.DBus;
>>member=GetNameOwner
>>   string ":1.48"
>>method return time=1598039669.280738 sender=org.freedesktop.DBus ->
>>destination=:1.3 serial=4294967295 reply_serial=777
>>   string ":1.48"
>>signal time=1598039669.280774 sender=:1.3 -> destination=(null
>>destination) serial=778 path=/org/freedesktop/systemd1;
>>interface=org.freedesktop.systemd1.Manager; member=UnitNew
>>   string "obmc-host-start at 0.target"
>>   object path
>>"/org/freedesktop/systemd1/unit/obmc_2dhost_2dstart_400_2etarget"
>>signal time=1598039669.280823 sender=:1.3 -> destination=(null
>>destination) serial=779 path=/org/freedesktop/systemd1;
>>interface=org.freedesktop.systemd1.Manager; member=JobNew
>>   uint32 1105
>>   object path "/org/freedesktop/systemd1/job/1105"
>>   string "obmc-host-start at 0.target"
>>method return time=1598039669.280883 sender=:1.3 ->
>destination=:1.48
>>serial=780 reply_serial=33
>>   object path "/org/freedesktop/systemd1/job/1105"
>>signal time=1598039669.281305 sender=:1.48 -> destination=(null
>>destination) serial=34 path=/xyz/openbmc_project/state/host0;
>>interface=org.freedesktop.DBus.Properties; member=PropertiesChanged
>>   string "xyz.openbmc_project.State.Host"
>>   array [
>>      dict entry(
>>         string "RequestedHostTransition"
>>         variant             string
>>"xyz.openbmc_project.State.Host.Transition.On"
>>      )
>>   ]
>>   array [
>>   ]