RE: [PATCH v7 07/13] cpufreq: amd-pstate: implement suspend and resume callbacks

[Yuan, Perry]

[Public]



> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Monday, December 12, 2022 11:15 PM
> To: Huang, Ray <Ray.Huang@xxxxxxx>; Yuan, Perry <Perry.Yuan@xxxxxxx>
> Cc: rafael.j.wysocki@xxxxxxxxx; viresh.kumar@xxxxxxxxxx; Sharma, Deepak
> <Deepak.Sharma@xxxxxxx>; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> Li (Jassmine) <Li.Meng@xxxxxxx>; Karny, Wyes <Wyes.Karny@xxxxxxx>;
> linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH v7 07/13] cpufreq: amd-pstate: implement suspend and
> resume callbacks
> 
> [Public]
> 
> 
> 
> > -----Original Message-----
> > From: Huang, Ray <Ray.Huang@xxxxxxx>
> > Sent: Monday, December 12, 2022 03:05
> > To: Yuan, Perry <Perry.Yuan@xxxxxxx>
> > Cc: rafael.j.wysocki@xxxxxxxxx; Limonciello, Mario
> > <Mario.Limonciello@xxxxxxx>; viresh.kumar@xxxxxxxxxx; Sharma,
> Deepak
> > <Deepak.Sharma@xxxxxxx>; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>;
> > Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> > <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>;
> Meng, Li
> > (Jassmine) <Li.Meng@xxxxxxx>; Karny, Wyes <Wyes.Karny@xxxxxxx>;
> > linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v7 07/13] cpufreq: amd-pstate: implement suspend
> > and resume callbacks
> >
> > On Thu, Dec 08, 2022 at 07:18:46PM +0800, Yuan, Perry wrote:
> > > From: Perry Yuan <Perry.Yuan@xxxxxxx>
> > >
> > > 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.
> > >
> > > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > > ---
> > >  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 412accab7bda..ea9255bdc9ac
> > > 100644
> > > --- a/drivers/cpufreq/amd-pstate.c
> > > +++ b/drivers/cpufreq/amd-pstate.c
> > > @@ -1273,6 +1273,44 @@ static int amd_pstate_epp_cpu_offline(struct
> > cpufreq_policy *policy)
> > >  	return amd_pstate_cpu_offline(policy);  }
> > >
> > > +static int amd_pstate_epp_suspend(struct cpufreq_policy *policy) {
> > > +	struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
> > > +	int ret;
> > > +
> > > +	/* avoid suspending when EPP is not enabled */
> > > +	if (!cppc_active)
> > > +		return 0;
> > > +
> > > +	/* set this flag to avoid setting core offline*/
> > > +	cpudata->suspended = true;
> > > +
> > > +	/* disable CPPC in lowlevel firmware */
> > > +	ret = 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 = all_cpu_data[policy->cpu];
> > > +
> > > +	if (cpudata->suspended) {
> > > +		mutex_lock(&amd_pstate_limits_lock);
> > > +
> > > +		/* enable amd pstate from suspend state*/
> > > +		amd_pstate_epp_reenable(cpudata);
> >
> > The same comment, could you please double confirm whether the
> > perfo_ctrls registers will be cleared while we execute a round of S3
> > suspend/resume?

PERF_CTL register will be always 0 if we do not load acpi_cpufreq driver after kernel booting. 
So suspend/resume will not change the PERF_CTL MSR as well.


> 
> And if they are; identify what is clearing them.  It might not be the same for
> s0i3 and S3.

I checked the PERF_CTRL with suspend/resume,  offline/online test.
The MSRs of all cores are not changed while amd-pstate driver loaded instead of acpi-cpufreq.


> 
> >
> > > +
> > > +		mutex_unlock(&amd_pstate_limits_lock);
> > > +
> > > +		cpudata->suspended = false;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static void amd_pstate_verify_cpu_policy(struct amd_cpudata *cpudata,
> > >  					   struct cpufreq_policy_data *policy)
> { @@ -1309,6 +1347,8
> > > @@ static struct cpufreq_driver
> > amd_pstate_epp_driver = {
> > >  	.update_limits	= amd_pstate_epp_update_limits,
> > >  	.offline	= amd_pstate_epp_cpu_offline,
> > >  	.online		= amd_pstate_epp_cpu_online,
> > > +	.suspend	= amd_pstate_epp_suspend,
> > > +	.resume		= amd_pstate_epp_resume,
> > >  	.name		= "amd_pstate_epp",
> > >  	.attr		= amd_pstate_epp_attr,
> > >  };
> > > --
> > > 2.34.1
> > >