linux-kernel - RE: [PATCH v3 6/8] cpufreq: amd-pstate: implement suspend and resume callbacks

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Date:   Sun, 13 Nov 2022 16:19:06 +0000
From:   "Yuan, Perry" <Perry.Yuan@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "Huang, Ray" <Ray.Huang@....com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>
CC:     "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Huang, Shimmer" <Shimmer.Huang@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "Meng, Li (Jassmine)" <Li.Meng@....com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 6/8] cpufreq: amd-pstate: implement suspend and resume
 callbacks

[AMD Official Use Only - General]

Hi Mario. 

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@....com>
> Sent: Tuesday, November 8, 2022 2:18 AM
> To: Yuan, Perry <Perry.Yuan@....com>; rafael.j.wysocki@...el.com; Huang,
> Ray <Ray.Huang@....com>; viresh.kumar@...aro.org
> Cc: Sharma, Deepak <Deepak.Sharma@....com>; Fontenot, Nathan
> <Nathan.Fontenot@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Huang, Shimmer
> <Shimmer.Huang@....com>; Du, Xiaojian <Xiaojian.Du@....com>; Meng,
> Li (Jassmine) <Li.Meng@....com>; linux-pm@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH v3 6/8] cpufreq: amd-pstate: implement suspend and
> resume callbacks
> 
> On 11/7/2022 11:57, Perry Yuan wrote:
> > 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@....com>
> 
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>

Thank you.
I pick up the RB tag in the V4.

Perry. 

> 
> > ---
> >   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 6ce9fca0a128..841b1e2383b8
> 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -1282,6 +1282,44 @@ 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);
> > +
> > +		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)
> >   {
> > @@ -1318,6 +1356,8 @@ 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,
> >   };