Re: [PATCH] cpufreq: intel_pstate: Fix processing for turbo activation ratio

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Mon, 2016-04-25 at 15:48 +0200, Rafael J. Wysocki wrote:
> On Sat, Apr 23, 2016 at 4:53 AM, Srinivas Pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> > 
> > When the config TDP level is not nominal (level = 0), the MSR
> > values for
> > reading level 1 and level 2 ratios contain power in low 14 bits and
> > actual
> > ratio bits are at bits [23:16]. The current processing for level 1
> > and
> > level 2 is wrong as there is no shift done to get actual ratio.
> > 
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel
> > .com>
> Since this is a fix, do we need it in v4.6?
> 
This impact the display of turbo_pct in Intel P-state sysfs. So if not
too late, I prefer for v4.6.
 
> Do we want it in -stable too and in what -stable if so?
4.4 onward.
> 

Thanks,
Srinivas

> 
> > 
> > ---
> >  drivers/cpufreq/intel_pstate.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/cpufreq/intel_pstate.c
> > b/drivers/cpufreq/intel_pstate.c
> > index 1b2767d..03f94c2 100644
> > --- a/drivers/cpufreq/intel_pstate.c
> > +++ b/drivers/cpufreq/intel_pstate.c
> > @@ -813,6 +813,10 @@ static int core_get_max_pstate(void)
> >                         if (err)
> >                                 goto skip_tar;
> > 
> > +                       /* For level 1 and 2, bits[23:16] contains
> > ratio */
> > +                       if (tdp_ctrl)
> > +                               tdp_ratio >>= 16;
> > +                       tdp_ratio &= 0xff; /* ratios are only 8
> > bits long */
> >                         if (tdp_ratio - 1 == tar) {
> >                                 max_pstate = tar;
> >                                 pr_debug("max_pstate=TAC %x\n",
> > max_pstate);
> > --