[Skiboot] [PATCH] [v3] Fast reboot for P8

[Shilpasri G Bhat]

On 09/28/2016 12:35 PM, Stewart Smith wrote:
> Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com> writes:
>> On 09/28/2016 10:24 AM, Stewart Smith wrote:
>>>>> We could reset the OCCs on fast reboot, as there is a PRD command to
>>>>>>> disable them.. although nobody should *ever* use them....
>>>>>
>>>>> We could ... should we ?
>>> Probably? I may have to think about it a bit more.
>>
>> Resetting OCC will put the system to Psafe frequency till it comes back and we
>> will need to wait till all the OCCs are up before we set all the cores to
>> nominal frequency. This will just increase the reboot time.
> 
> There is that....
> 
> Any reason we couldn't hotplug into Linux the data from OCC? We could
> improve IPL time that way too (OCC load+start time is fairly significant chunk)
> 

We wait for all OCCs to be up in OPAL mainly for two reasons:
1) Parse pstate table and populate DT for cpufreq consumption.
2) To set all cores to nominal frequency so that the system boots with nominal
frequency

So yes 1) can be done when cpufreq inits and OPAL need not wait for OCC;
provided 2) is done by OCC itself after it boots up.

Thanks and Regards,
Shilpa