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

From	Gautham R Shenoy <ego@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to power9_idle_stop
Date	2016-10-13 18:50 +0200
Message-ID	<srRmF-5Xf-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <smDDH-QX-3@gated-at.bofh.it> <soweK-23L-25@gated-at.bofh.it> <soweK-23L-23@gated-at.bofh.it> <spxLs-5eW-1@gated-at.bofh.it> <srmCd-1kH-5@gated-at.bofh.it>
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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.

Thread

[PATCH 0/2] powernv:stop: Use psscr_val,mask provided by firmware "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> - 2016-09-29 09:10 +0200
  [PATCH 2/2] powernv: Pass PSSCR value and mask to power9_idle_stop "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> - 2016-09-29 09:10 +0200
    Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to  power9_idle_stop Balbir Singh <bsingharora@gmail.com> - 2016-10-04 13:40 +0200
      Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to  power9_idle_stop Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-10-07 09:30 +0200
        Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to power9_idle_stop Stewart Smith <stewart@linux.vnet.ibm.com> - 2016-10-12 10:00 +0200
          Re: [PATCH 2/2] powernv: Pass PSSCR value and mask to  power9_idle_stop Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-10-13 18:50 +0200
  [PATCH 1/2] powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> - 2016-09-29 09:10 +0200

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