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From:   Len Brown <lenb@kernel.org>
Date:   Fri, 12 Mar 2021 17:15:51 -0500
Message-ID: <CAJvTdKkpbFqDRL9BP3Ri0Yeb0VMXv79dr+C=ym2+GWMRZEEYpw@mail.gmail.com>
Subject: Re: [PATCH] tools/power/x86/turbostat: Fix TCC offset bit mask
To:     Doug Smythies <dsmythies@telus.net>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>
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Doug,
The offset works for control.

However, it is erroneous to use it for reporting of the actual
temperature, like I did in turbostat.
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