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From:   "Yuan, Perry" <Perry.Yuan@amd.com>
To:     "Huang, Ray" <Ray.Huang@amd.com>
CC:     "rafael.j.wysocki@intel.com" <rafael.j.wysocki@intel.com>,
        "viresh.kumar@linaro.org" <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>,
        "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-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RESEND PATCH V2 2/9] cpufreq: amd_pstate: add module parameter
 to load amd pstate EPP driver
Thread-Topic: [RESEND PATCH V2 2/9] cpufreq: amd_pstate: add module parameter
 to load amd pstate EPP driver
Thread-Index: AQHY3MScv4q6idw2vkK9CXgEWYjnha4SYVSAgAUdjiA=
Date:   Thu, 20 Oct 2022 15:56:21 +0000
Message-ID: <DM4PR12MB5278526E62147200D16FF2B99C2A9@DM4PR12MB5278.namprd12.prod.outlook.com>
References: <20221010162248.348141-1-Perry.Yuan@amd.com>
 <20221010162248.348141-3-Perry.Yuan@amd.com> <Y00koVkHD3ECCY7H@amd.com>
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[AMD Official Use Only - General]

Hi Ray.=20

> -----Original Message-----
> From: Huang, Ray <Ray.Huang@amd.com>
> Sent: Monday, October 17, 2022 5:47 PM
> To: Yuan, Perry <Perry.Yuan@amd.com>
> Cc: rafael.j.wysocki@intel.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>; 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: [RESEND PATCH V2 2/9] cpufreq: amd_pstate: add module
> parameter to load amd pstate EPP driver
>=20
> On Tue, Oct 11, 2022 at 12:22:41AM +0800, Yuan, Perry wrote:
> > The amd_pstate mode parameter will allow user to select which amd
> > pstate working mode as booting mode, amd_pstate instance or
> amd_pstate_epp instance.
> >
> > 1) amd_pstate instance is depending on the target operation mode.
> > 2) amd_pstate_epp instance is depending on the set_policy operation
> mode.It
> >    is also called active mode that AMD SMU has EPP algorithm to control=
 the
> >    CPU runtime frequency according to the EPP set value and workload.
> >
>=20
> There is one concern here: how can the user know which kind of processor
> supports the EPP function in hardware?
>=20
> Thanks,
> Ray

Checked with internal team, I was told that EPP is part of the CPPC impleme=
ntation,=20
The Pstate driver already check if the cppc valid when driver loading, we d=
o not need to check the epp again.=20

Perry.

>=20
> > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index f52b8f2fe529..2d28f458589c 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -63,6 +63,10 @@ module_param(shared_mem, bool, 0444);
> > MODULE_PARM_DESC(shared_mem,
> >  		 "enable amd-pstate on processors with shared memory
> solution
> > (false =3D disabled (default), true =3D enabled)");
> >
> > +static bool epp =3D false;
> > +module_param(epp, bool, 0444);
> > +MODULE_PARM_DESC(epp, "Enable energy performance preference (EPP)
> > +control");
> > +
> >  static struct cpufreq_driver amd_pstate_driver;
> >
> >  /**
> > --
> > 2.34.1
> >