Re: [PATCH 0/4] ppc/pnv: Add chiptod and core timebase state machine models

["Nicholas Piggin" <npiggin@gmail.com>]

On Tue Jun 6, 2023 at 11:59 PM AEST, Cédric Le Goater wrote:
> On 6/4/23 01:36, Nicholas Piggin wrote:
> > This adds support for chiptod and core timebase state machine models in
> > the powernv POWER9 and POWER10 models.
> > 
> > This does not actually change the time or the value in TB registers
> > (because they are alrady synced in QEMU), but it does go through the
> > motions. It is enough to be able to run skiboot's chiptod initialisation
> > code that synchronises core timebases (after a patch to prevent skiboot
> > skipping chiptod for QEMU, posted to skiboot mailing list).
> > 
> > Sorry there was some delay since the last posting. There is a bit more
> > interest in this recently but feedback and comments from RFC was not
> > forgotten and is much appreciated.
> > 
> > https://lists.gnu.org/archive/html/qemu-ppc/2022-08/msg00324.html
> > 
> > I think I accounted for everything except moving register defines to the
> > .h file. I'm on the fence about that but if they are only used in the .c
> > file I think it's okay to keep them there for now. I cut out a lot of
> > unused ones so it's not so cluttered now.
> > 
> > Lots of other changes and fixes since that RFC. Notably:
> > - Register names changed to match the workbook names instead of skiboot.
> > - TFMR moved to timebase_helper.c from misc_helper.c
> > - More comprehensive model and error checking, particularly of TFMR.
> > - POWER10 with multi-chip support.
> > - chiptod and core timebase linked via specific state instead of TFMR.
>
>
> The chiptod units are not exposed to the OS, it is all handled at FW
> level AFAIK. Could the OPAL people provide some feedback on the low level
> models ?

Well, no takers so far. I guess I'm a OPAL people :)

I did some of the P10 chiptod addressing in skiboot, at least. This
patch does work with the skiboot chiptod driver at least.

I would eventually like to add in the ability to actually change the
TB with it, and inject errors and generate HMIs because that's an area
that seem to be a bit lacking (most of such testing seemed to be done
on real hardware using special time facility corruption injection).

But yes for now it is a bit difficult to verify it does much useful
aside from booting skiboot (+ patch to enable chiptod on QEMU I posted
recently).

Thanks,
Nick