linux-kernel - Re: [PATCH v2 0/3] Power10 basic energy management

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Date:   Mon, 13 Jul 2020 15:23:21 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     benh@...nel.crashing.org, ego@...ux.vnet.ibm.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        mikey@...ling.org, mpe@...erman.id.au, paulus@...ba.org,
        pratik.r.sampat@...il.com,
        Pratik Rajesh Sampat <psampat@...ux.ibm.com>,
        ravi.bangoria@...ux.ibm.com, svaidy@...ux.ibm.com
Subject: Re: [PATCH v2 0/3] Power10 basic energy management

Excerpts from Pratik Rajesh Sampat's message of July 10, 2020 3:22 pm:
> Changelog v1 --> v2:
> 1. Save-restore DAWR and DAWRX unconditionally as they are lost in
> shallow idle states too
> 2. Rename pnv_first_spr_loss_level to pnv_first_fullstate_loss_level to
> correct naming terminology
> 
> Pratik Rajesh Sampat (3):
>   powerpc/powernv/idle: Exclude mfspr on HID1,4,5 on P9 and above
>   powerpc/powernv/idle: save-restore DAWR0,DAWRX0 for P10
>   powerpc/powernv/idle: Rename pnv_first_spr_loss_level variable
> 
>  arch/powerpc/platforms/powernv/idle.c | 34 +++++++++++++++++----------
>  1 file changed, 22 insertions(+), 12 deletions(-)

These look okay to me, but the CPU_FTR_ARCH_300 test for 
pnv_power9_idle_init() is actually wrong, it should be a PVR test 
because idle is not completely architected (not even shallow stop 
states, unfortunately).

It doesn't look like we support POWER10 idle correctly yet, and on older
kernels it wouldn't work even if we fixed newer, so ideally the PVR 
check would be backported as a fix in the front of the series.

Sadly, we have no OPAL idle driver yet. Hopefully we will before the
next processor shows up :P

Thanks,
Nick