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

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Date:   Tue, 14 Jul 2020 02:50:00 +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 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 Sampat's message of July 13, 2020 8:02 pm:
> Thank you for your comments,
> 
> On 13/07/20 10:53 am, Nicholas Piggin wrote:
>> 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
> 
> So if I understand this correctly, in powernv/idle.c where we check for
> CPU_FTR_ARCH_300, we should rather be making a pvr_version_is(PVR_POWER9)
> check instead?
> 
> Of course, the P10 PVR and its relevant checks will have to be added then too.

Yes I think so, unfortunately.

Thanks,
Nick