RE: [PATCH] cpufreq: amd_pstate: Fix initial highest_perf value

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Rafael,

> -----Original Message-----
> From: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Sent: Thursday, August 25, 2022 7:59 PM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: Rafael Wysocki <rafael.j.wysocki@xxxxxxxxx>; Huang, Ray
> <Ray.Huang@xxxxxxx>; Viresh Kumar <viresh.kumar@xxxxxxxxxx>; Sharma,
> Deepak <Deepak.Sharma@xxxxxxx>; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Su, Jinzhou (Joe) <Jinzhou.Su@xxxxxxx>;
> Huang, Shimmer <Shimmer.Huang@xxxxxxx>; Du, Xiaojian
> <Xiaojian.Du@xxxxxxx>; Meng, Li (Jassmine) <Li.Meng@xxxxxxx>; Linux
> PM <linux-pm@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-
> kernel@xxxxxxxxxxxxxxx>
> Subject: Re: [PATCH] cpufreq: amd_pstate: Fix initial highest_perf value
> 
> [CAUTION: External Email]
> 
> On Sun, Aug 14, 2022 at 6:57 PM Perry Yuan <Perry.Yuan@xxxxxxx> wrote:
> >
> > To avoid some new AMD processors use wrong highest perf when amd
> > pstate driver loaded, this fix will query the highest perf from MSR
> > register
> > MSR_AMD_CPPC_CAP1 and cppc_acpi interface firstly, then compare with
> > the highest perf value got by calling amd_get_highest_perf() function.
> >
> > The lower value will be the correct highest perf we need to use.
> > Otherwise the CPU max MHz will be incorrect if the
> > amd_get_highest_perf() did not cover the new process family and model
> ID.
> >
> > Like this lscpu info, the max frequency is incorrect.
> >
> > Vendor ID:               AuthenticAMD
> >     Socket(s):           1
> >     Stepping:            2
> >     CPU max MHz:         5410.0000
> >     CPU min MHz:         400.0000
> >     BogoMIPS:            5600.54
> >
> > Fixes: 3743d55b289c2 (x86, sched: Fix the AMD CPPC maximum
> performance
> > value on certain AMD Ryzen generations)
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> 
> This needs to be reviewed by the AMD P-state driver maintainer.

There is one small change for this patch , will send V2 for further review.

Perry. 


> 
> > ---
> >  drivers/cpufreq/amd-pstate.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 9f4375f7ab46..f778ab37e436 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -354,6 +354,7 @@ static inline int amd_pstate_enable(bool enable)
> > static int pstate_init_perf(struct amd_cpudata *cpudata)  {
> >         u64 cap1;
> > +       u32 highest_perf;
> >
> >         int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
> >                                      &cap1); @@ -365,7 +366,11 @@
> > static int pstate_init_perf(struct amd_cpudata *cpudata)
> >          *
> >          * CPPC entry doesn't indicate the highest performance in some ASICs.
> >          */
> > -       WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());
> > +       highest_perf = amd_get_highest_perf();
> > +       if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
> > +               highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
> > +
> > +       WRITE_ONCE(cpudata->highest_perf, highest_perf);
> >
> >         WRITE_ONCE(cpudata->nominal_perf,
> AMD_CPPC_NOMINAL_PERF(cap1));
> >         WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> > AMD_CPPC_LOWNONLIN_PERF(cap1)); @@ -377,12 +382,17 @@ static int
> > pstate_init_perf(struct amd_cpudata *cpudata)  static int
> > cppc_init_perf(struct amd_cpudata *cpudata)  {
> >         struct cppc_perf_caps cppc_perf;
> > +       u32 highest_perf;
> >
> >         int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> >         if (ret)
> >                 return ret;
> >
> > -       WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf());
> > +       highest_perf = amd_get_highest_perf();
> > +       if (highest_perf > cppc_perf.highest_perf)
> > +               highest_perf = cppc_perf.nominal_perf;
> > +
> > +       WRITE_ONCE(cpudata->highest_perf, highest_perf);
> >
> >         WRITE_ONCE(cpudata->nominal_perf, cppc_perf.nominal_perf);
> >         WRITE_ONCE(cpudata->lowest_nonlinear_perf,
> > --
> > 2.34.1
> >