Fix the wrong lowest perf value reading which is used for new
des_perf calculation by governor requested, the incorrect min_perf will
get incorrect des_perf to be set , that will cause the system frequency
changing unexpectedly.

Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
Signed-off-by: Su Jinzhou <jinzhou.su@amd.com>
---
 drivers/cpufreq/amd-pstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 5cdef6638681..183cdd4ba00e 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -307,7 +307,7 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
 		return -ENODEV;
 
 	cap_perf = READ_ONCE(cpudata->highest_perf);
-	min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
+	min_perf = READ_ONCE(cpudata->lowest_perf);
 	max_perf = cap_perf;
 
 	freqs.old = policy->cur;
-- 
2.34.1

Hi Perry,

Perry Yuan <Perry.Yuan@amd.com> writes:

> Fix the wrong lowest perf value reading which is used for new
> des_perf calculation by governor requested, the incorrect min_perf will
> get incorrect des_perf to be set , that will cause the system frequency
> changing unexpectedly.
>
> Reviewed-by: Huang Rui <ray.huang@amd.com>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> Signed-off-by: Su Jinzhou <jinzhou.su@amd.com>
> ---
>  drivers/cpufreq/amd-pstate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 5cdef6638681..183cdd4ba00e 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -307,7 +307,7 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
>  		return -ENODEV;
>  
>  	cap_perf = READ_ONCE(cpudata->highest_perf);
> -	min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
> +	min_perf = READ_ONCE(cpudata->lowest_perf);
>  	max_perf = cap_perf;
>  
>  	freqs.old = policy->cur;

This looks to be a pretty big change (lowest nonlinear vs lowest). Does
the patch need to be backported to older kernels?

[AMD Official Use Only - General]

Hi Agrawal,

> -----Original Message-----
> From: Punit Agrawal <punit.agrawal@bytedance.com>
> Sent: Monday, August 15, 2022 11:05 PM
> To: Yuan, Perry <Perry.Yuan@amd.com>
> Cc: rafael.j.wysocki@intel.com; Huang, Ray <Ray.Huang@amd.com>;
> viresh.kumar@linaro.org; Sharma, Deepak <Deepak.Sharma@amd.com>;
> Limonciello, Mario <Mario.Limonciello@amd.com>; Fontenot, Nathan
> <Nathan.Fontenot@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Su, Jinzhou (Joe) <Jinzhou.Su@amd.com>;
> Huang, Shimmer <Shimmer.Huang@amd.com>; Du, Xiaojian
> <Xiaojian.Du@amd.com>; Meng, Li (Jassmine) <Li.Meng@amd.com>; linux-
> pm@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v5 4/7] cpufreq: amd_pstate: fix wrong lowest perf fetch
> 
> [CAUTION: External Email]
> 
> Hi Perry,
> 
> Perry Yuan <Perry.Yuan@amd.com> writes:
> 
> > Fix the wrong lowest perf value reading which is used for new des_perf
> > calculation by governor requested, the incorrect min_perf will get
> > incorrect des_perf to be set , that will cause the system frequency
> > changing unexpectedly.
> >
> > Reviewed-by: Huang Rui <ray.huang@amd.com>
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> > Signed-off-by: Su Jinzhou <jinzhou.su@amd.com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 5cdef6638681..183cdd4ba00e 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -307,7 +307,7 @@ static int amd_pstate_target(struct cpufreq_policy
> *policy,
> >               return -ENODEV;
> >
> >       cap_perf = READ_ONCE(cpudata->highest_perf);
> > -     min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
> > +     min_perf = READ_ONCE(cpudata->lowest_perf);
> >       max_perf = cap_perf;
> >
> >       freqs.old = policy->cur;
> 
> This looks to be a pretty big change (lowest nonlinear vs lowest). Does the patch
> need to be backported to older kernels?

The patch fixes the min perf initial value, the correct min perf is lowest_perf which is captured through MSR_AMD_CPPC_CAP1 register or the cppc_get_perf_caps().
Yes, the patch will need to be backported to other kernel branch as issue fix.
Sorry to response late.

Perry.

"Yuan, Perry" <Perry.Yuan@amd.com> writes:

[...]

>> Perry Yuan <Perry.Yuan@amd.com> writes:
>> 
>> > Fix the wrong lowest perf value reading which is used for new des_perf
>> > calculation by governor requested, the incorrect min_perf will get
>> > incorrect des_perf to be set , that will cause the system frequency
>> > changing unexpectedly.
>> >
>> > Reviewed-by: Huang Rui <ray.huang@amd.com>
>> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>> > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
>> > Signed-off-by: Su Jinzhou <jinzhou.su@amd.com>
>> > ---
>> >  drivers/cpufreq/amd-pstate.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/cpufreq/amd-pstate.c
>> > b/drivers/cpufreq/amd-pstate.c index 5cdef6638681..183cdd4ba00e 100644
>> > --- a/drivers/cpufreq/amd-pstate.c
>> > +++ b/drivers/cpufreq/amd-pstate.c
>> > @@ -307,7 +307,7 @@ static int amd_pstate_target(struct cpufreq_policy
>> *policy,
>> >               return -ENODEV;
>> >
>> >       cap_perf = READ_ONCE(cpudata->highest_perf);
>> > -     min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
>> > +     min_perf = READ_ONCE(cpudata->lowest_perf);
>> >       max_perf = cap_perf;
>> >
>> >       freqs.old = policy->cur;
>> 
>> This looks to be a pretty big change (lowest nonlinear vs lowest). Does the patch
>> need to be backported to older kernels?
>
> The patch fixes the min perf initial value, the correct min perf is lowest_perf which is captured through MSR_AMD_CPPC_CAP1 register or the cppc_get_perf_caps().
> Yes, the patch will need to be backported to other kernel branch as issue fix.

Great, thanks for confirming!

[...]