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

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Date:   Mon, 13 Jul 2020 15:32:12 +0530
From:   Pratik Sampat <psampat@...ux.ibm.com>
To:     Nicholas Piggin <npiggin@...il.com>, 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,
        ravi.bangoria@...ux.ibm.com, svaidy@...ux.ibm.com
Subject: Re: [PATCH v2 0/3] Power10 basic energy management

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.

Thanks
Pratik