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SubjectRE: [PATCH v4 4/9] cpufreq: amd_pstate: implement Pstate EPP support for the AMD processors
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[AMD Official Use Only - General]



> -----Original Message-----
> From: Karny, Wyes <Wyes.Karny@amd.com>
> Sent: Thursday, November 17, 2022 10:03 PM
> To: Yuan, Perry <Perry.Yuan@amd.com>; rafael.j.wysocki@intel.com;
> Limonciello, Mario <Mario.Limonciello@amd.com>; Huang, Ray
> <Ray.Huang@amd.com>; viresh.kumar@linaro.org
> Cc: Sharma, Deepak <Deepak.Sharma@amd.com>; Fontenot, Nathan
> <Nathan.Fontenot@amd.com>; Deucher, Alexander
> <Alexander.Deucher@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 v4 4/9] cpufreq: amd_pstate: implement Pstate EPP support
> for the AMD processors
>
> Hi Perry,
>
> On 11/10/2022 11:28 PM, Perry Yuan wrote:
> [snip]
> > +
> > +static ssize_t store_energy_performance_preference(
> > + struct cpufreq_policy *policy, const char *buf, size_t count) {
> > + struct amd_cpudata *cpudata = policy->driver_data;
> > + char str_preference[21];
> > + ssize_t ret;
> > + u32 epp = 0;
>
> Here `epp` is a unused variable.
> [snip]
> > @@ -657,6 +1281,20 @@ static int __init amd_pstate_param(char *str)
> > if (!str)
> > return -EINVAL;
> >
> > + /*
> > + * Disable amd-pstate driver by default for now
> > + * append amd-pstate=active or amd-pstate=active
> > + * to enable driver loaded
> > + */
> > + if (!strcmp(str, "active")) {
> > + cppc_load = 1;
> > + default_pstate_driver = &amd_pstate_epp_driver;
> > + } else if (!strcmp(str, "passive")) {
> > + epp_off = 1;
> > + cppc_load = 1;
> > + default_pstate_driver = &amd_pstate_driver;
> > + }
> > +
> > /*
> > * support shared memory type CPPC which has no MSR function.
> > * enable amd-pstate on processors with shared memory solution
>
> In the shared memory support section also `cppc_load` has to be set otherwise
> amd_pstate=legacy_cppc will not work.
If the patches just got reviewed are accepted, the legacy_cppcc will not be needed any more.
I will rebase the EPP patches based on the that.


>
> if (!strcmp(str, "legacy_cppc")) {
> shared_mem = true;
> cppc_load = 1;
> }

Previous plan was to add two parameters to kernel command line,
passive or active and legacy_cppc for shared memory platform.

>
>
> --
> Thanks & Regards,
> Wyes

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