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Subject: Re: adding sync method in phosphor-time-manager
To: <openbmc@lists.ozlabs.org>
References: <PU1PR04MB2248961AEF87BA87C7749050A70D0@PU1PR04MB2248.apcprd04.prod.outlook.com>
 <20201007013446.GE6152@heinlein>
From: Alexander Amelkin <a.amelkin@yadro.com>
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Date: Thu, 8 Apr 2021 21:08:24 +0300
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Hi Patrick, everybody!

As far as I can see, this discussion has had no development, to our regret.
We would really like to read some clarification on what is the proposed 
method
of timekeeping for x86 systems nowadays, because with TimeOwner interface
removed, it's not clear to me anymore.

Do you allow the users to set time/date on the BMC side? If so, how do you
propagate those changes on to the host, which in x86 is the owner of RTC?
What if the BMC is rebooted before the time settings are propagated?

If you don't allow setting the time in BMC, then what are the options 
for the user?
Do you allow a choice between NTP and Host time only?

How and when is the time synced from the host? Is there a method to 
force a sync?

Is there maybe some document that covers this topic?

WBR, Alexander Amelkin
YADRO

07.10.2020 04:34, Patrick Williams пишет:
> On Tue, Oct 06, 2020 at 05:38:13PM +0000, Velumani T-ERS,HCLTech wrote:
>> Classification:
>> Hi Team,
>>
>> We wanted to add another time sync method in phosphor-time-manager to get the time from the host and set it to BMC. To have this option configurable I propose a dbus property in the time interface(given below). Please provide your feedback/comments.
>>
>> https://github.com/openbmc/phosphor-dbus-interfaces/blob/master/xyz/openbmc_project/Time/Synchronization.interface.yaml
>> enumerations:
>>      - name: Method
>>        description: >
>>          Possible methods of time synchronization.
>>        values:
>>          - name: NTP
>>            description: >
>>              Sync by using the Network Time Protocol.
>>          - name: Manual
>>            description: >
>>              Sync time manually.
>>           - name: HostSync
>>            description: >
>>              Sync the time from host.
>>
> Hopefully Vishwa can weigh in here.
>
> It is my understanding that the default implementation allows the host
> to synchronize the time down already.  There use to be an interface that
> determined the "TimeOwner" to specify if the BMC or the Host were in
> charge of the time.  That was removed not too long ago.
>
> https://github.com/openbmc/phosphor-dbus-interfaces/commit/70c76a29b898f05e28c803808bd57a2b6c3f7a6f
>
> I think you should look through the history on this commit (it
> references a discussion related to the mailing list) and check with the
> people in that chain as to why it was removed before we add back in
> something very similar.
>