[Skiboot] [PATCH] fast-boot: occ: Re-parse the pstate table during fast-boot

Nicholas Piggin npiggin at gmail.com
Sat Feb 3 17:24:25 AEDT 2018

On Fri,  2 Feb 2018 12:32:32 +0530
Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com> wrote:

> OCC shares the frequency list to host by copying the pstate table to
> main memory in HOMER. This table is parsed during boot to create
> device-tree properties for frequency and pstate IDs. OCC can update
> the pstate table to present a new set of frequencies to the host. But
> host will remain oblivious to these changes unless it is re-inited
> with the updated device-tree CPU frequency properties. So this patch
> allows to re-parse the pstate table and update the device-tree
> properties during fast-reboot.
> OCC updates the pstate table when asked to do so using pstate-table
> bias command. And this is mainly used by WOF team for
> characterization purposes.

Would this ever be used in production, I'm guessing not? I don't
think that's a bad thing as such -- designing for test is always
good. Perhaps a comment though to explain why you're re-parsing

Without knowing much about OCC, I'll guess you're doing this so
you can update the OCC at runtime without having to update firmware
before each IPL?

I guess we should always keep in mind fast reboot should match IPL
as closely as possible and any undetected deviations are a pretty
serious flaw. (e.g., you mess up your OCC state and want to return
to normal, you would reboot).

I'm just wondering, should this be under an nvram option?


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