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From:   Doug Smythies <dsmythies@telus.net>
Date:   Sat, 13 Mar 2021 07:16:27 -0800
Message-ID: <CAAYoRsXX74eDQ_vCdLnyNQhMutwE4TWMZsB7HeW5tu4kxVEFJQ@mail.gmail.com>
Subject: Re: [PATCH] tools/power/x86/turbostat: Fix TCC offset bit mask
To:     Len Brown <lenb@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        dsmythies <dsmythies@telus.net>
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On Fri, Mar 12, 2021 at 2:16 PM Len Brown <lenb@kernel.org> wrote:
>
> Doug,
> The offset works for control.
>
> However, it is erroneous to use it for reporting of the actual
> temperature, like I did in turbostat.

Agreed.
I have been running with a correction for that for a while,
and as discussed on Rui's thread.
But this bit mask correction patch is still needed isn't it?
for this:
cpu4: MSR_IA32_TEMPERATURE_TARGET: 0x1a64100d (90 C) (100 default - 10 offset)
which should be this:
cpu4: MSR_IA32_TEMPERATURE_TARGET: 0x1a64100d (74 C) (100 default - 26 offset)

But yes, I do now see the field size is only 4 bits for some parts.

... Doug

> Thus, I'm going to revert the patch that added it's use in turbostat
> for the Temperature column.
>
> thanks,
> -Len
>
> On Fri, Mar 12, 2021 at 1:26 AM Doug Smythies <dsmythies@telus.net> wrote:
> >
> > Hi Len,
> >
> >
> > thank you for your reply.
> >
> > On Thu, Mar 11, 2021 at 3:19 PM Len Brown <lenb@kernel.org> wrote:
> > >
> > > Thanks for the close read, Doug.
> > >
> > > This field size actually varies from system to system,
> > > but the reality is that the offset is never that big, and so the
> > > smaller mask is sufficient.
> >
> > Disagree.
> >
> > I want to use an offset of 26.
> >
> > > Finally, this may all be moot, because there is discussion that using
> > > the offset this way is simply erroneous.
> >
> > Disagree.
> > It works great.
> > As far as I know/recall I was the only person that responded to Rui's thread
> > "thermal/intel: introduce tcc cooling driver" [1]
> > And, I spent quite a bit of time doing so.
> > However, I agree the response seems different between the two systems
> > under test, Rui's and mine.
> >
> > [1] https://marc.info/?l=linux-pm&m=161070345329806&w=2
> >
> > >  stay tuned.
> >
> > O.K.
> >
> > ... Doug
> > >
> > > -Len
> > >
> > >
> > > On Sat, Jan 16, 2021 at 12:07 PM Doug Smythies <doug.smythies@gmail.com> wrote:
> > > >
> > > > The TCC offset mask is incorrect, resulting in
> > > > incorrect target temperature calculations, if
> > > > the offset is big enough to exceed the mask size.
> > > >
> > > > Signed-off-by: Doug Smythies <dsmythies@telus.net>
> > > > ---
> > > >  tools/power/x86/turbostat/turbostat.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
> > > > index 389ea5209a83..d7acdd4d16c4 100644
> > > > --- a/tools/power/x86/turbostat/turbostat.c
> > > > +++ b/tools/power/x86/turbostat/turbostat.c
> > > > @@ -4823,7 +4823,7 @@ int read_tcc_activation_temp()
> > > >
> > > >         target_c = (msr >> 16) & 0xFF;
> > > >
> > > > -       offset_c = (msr >> 24) & 0xF;
> > > > +       offset_c = (msr >> 24) & 0x3F;
> > > >
> > > >         tcc = target_c - offset_c;
> > > >
> > > > --
> > > > 2.25.1
> > > >
> > >
> > >
> > > --
> > > Len Brown, Intel Open Source Technology Center
>
>
>
> --
> Len Brown, Intel Open Source Technology Center