Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to power9_idle_stop

Hi Stewart,

On Wed, Oct 12, 2016 at 04:35:35PM +1100, Stewart Smith wrote:

What if we just treat the 0xF state from firmware as special and set it
to DEFAULT_PSSCR_MASK in that case? That deals with old skiboot, new
kernel, and sets a pretty small special case that's easy to track into
the future as something we should watch out for.

Yes, that will work. I will use this approach in the next version.

Additionally, if we make skiboot set sane values in ~DEFAULT_PSSCR_MASK
for valid fields in PSSCR on boot/(also kexec?), then
we should end up in a situation where everything works with everything
(even if you don't get the best power saving). Specifically, new
skiboot, old kernel... but it looks like there's nothing currently
missing there

No we're not missing much there. From the code of the old kernel, I
see that if we pass the psscr_val instead of just the RL to
power9_idle_stop(), we end up saving all the SPRs in
power_enter_stop() even if the psscr_val didn't correspond to a deep
idle state.

But that should be ok.

Should this patch also have Fixes: 3005c597ba4 and CC to stable?

Yes, thanks for pointing it out. I shall mark the next version to
stable.

-- 
Stewart Smith
OPAL Architect, IBM.

--
Thanks and Regards
gautham.