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From:   "Yuan, Perry" <Perry.Yuan@amd.com>
To:     Viresh Kumar <viresh.kumar@linaro.org>,
        "Limonciello, Mario" <Mario.Limonciello@amd.com>
CC:     "rafael.j.wysocki@intel.com" <rafael.j.wysocki@intel.com>,
        "Huang, Ray" <Ray.Huang@amd.com>,
        "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>,
        "Karny, Wyes" <Wyes.Karny@amd.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v9 08/13] cpufreq: amd-pstate: implement suspend and
 resume callbacks
Thread-Topic: [PATCH v9 08/13] cpufreq: amd-pstate: implement suspend and
 resume callbacks
Thread-Index: AQHZGH8OUW0eOYfoXk6+O7KzViQfyK6BC3CAgA7qLcA=
Date:   Thu, 5 Jan 2023 15:08:58 +0000
Message-ID: <DM4PR12MB527827691DAD904349E425519CFA9@DM4PR12MB5278.namprd12.prod.outlook.com>
References: <20221225163442.2205660-1-perry.yuan@amd.com>
 <20221225163442.2205660-9-perry.yuan@amd.com>
 <20221227025211.jjkmwtwg6whgavgd@vireshk-i7>
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[AMD Official Use Only - General]

Hi Viresh.=20

> -----Original Message-----
> From: Viresh Kumar <viresh.kumar@linaro.org>
> Sent: Tuesday, December 27, 2022 10:52 AM
> To: Yuan, Perry <Perry.Yuan@amd.com>
> Cc: rafael.j.wysocki@intel.com; Limonciello, Mario
> <Mario.Limonciello@amd.com>; Huang, Ray <Ray.Huang@amd.com>;
> 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>; Karny, Wyes <Wyes.Karny@amd.com>;
> linux-pm@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v9 08/13] cpufreq: amd-pstate: implement suspend and
> resume callbacks
>=20
> On 26-12-22, 00:34, Perry Yuan wrote:
> > From: Perry Yuan <Perry.Yuan@amd.com>
> >
> > add suspend and resume support for the AMD processors by
> > amd_pstate_epp driver instance.
> >
> > When the CPPC is suspended, EPP driver will set EPP profile to 'power'
> > profile and set max/min perf to lowest perf value.
> > When resume happens, it will restore the MSR registers with previous
> > cached value.
> >
> > Acked-by: Huang Rui <ray.huang@amd.com>
> > Reviewed-by: Mario Limonciello <Mario.Limonciello@amd.com>
> > Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 40
> > ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index c671f4955766..e3676d1a85c7 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -1041,6 +1041,44 @@ static int amd_pstate_epp_verify_policy(struct
> cpufreq_policy_data *policy)
> >  	return 0;
> >  }
> >
> > +static int amd_pstate_epp_suspend(struct cpufreq_policy *policy) {
> > +	struct amd_cpudata *cpudata =3D policy->driver_data;
> > +	int ret;
> > +
> > +	/* avoid suspending when EPP is not enabled */
> > +	if (cppc_state !=3D AMD_PSTATE_ACTIVE)
> > +		return 0;
> > +
> > +	/* set this flag to avoid setting core offline*/
> > +	cpudata->suspended =3D true;
> > +
> > +	/* disable CPPC in lowlevel firmware */
> > +	ret =3D amd_pstate_enable(false);
> > +	if (ret)
> > +		pr_err("failed to suspend, return %d\n", ret);
> > +
> > +	return 0;
> > +}
> > +
> > +static int amd_pstate_epp_resume(struct cpufreq_policy *policy) {
> > +	struct amd_cpudata *cpudata =3D policy->driver_data;
> > +
> > +	if (cpudata->suspended) {
>=20
> When will resume get called without being suspended first ?

Sorry for the late reply.
Theoretically the resume() will get called when system suspended firstly.
Checking cpudata->suspended flag to make sure eachtime resume() is called t=
o resume the previous MSR values safely in my view.
Maybe we can drop the checking code, but it will take more time to run test=
ing~ =20
So to be safe , we can keep this, I will try to do some optimization in fut=
ure.=20


Perry.=20

>=20
> > +		mutex_lock(&amd_pstate_limits_lock);
> > +
> > +		/* enable amd pstate from suspend state*/
> > +		amd_pstate_epp_reenable(cpudata);
> > +
> > +		mutex_unlock(&amd_pstate_limits_lock);
> > +
> > +		cpudata->suspended =3D false;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  static struct cpufreq_driver amd_pstate_driver =3D {
> >  	.flags		=3D CPUFREQ_CONST_LOOPS |
> CPUFREQ_NEED_UPDATE_LIMITS,
> >  	.verify		=3D amd_pstate_verify,
> > @@ -1062,6 +1100,8 @@ static struct cpufreq_driver
> amd_pstate_epp_driver =3D {
> >  	.exit		=3D amd_pstate_epp_cpu_exit,
> >  	.offline	=3D amd_pstate_epp_cpu_offline,
> >  	.online		=3D amd_pstate_epp_cpu_online,
> > +	.suspend	=3D amd_pstate_epp_suspend,
> > +	.resume		=3D amd_pstate_epp_resume,
> >  	.name		=3D "amd_pstate_epp",
> >  	.attr		=3D amd_pstate_epp_attr,
> >  };
> > --
> > 2.34.1
>=20
> --
> viresh