linux-kernel - Re: [PATCH v2 2/4] cpufreq: amd-pstate: Set a fallback policy based on preferred

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Date:   Tue, 20 Jun 2023 23:36:59 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>
Cc:     "Yuan, Perry" <Perry.Yuan@....com>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Karny, Wyes" <Wyes.Karny@....com>,
        "Shenoy, Gautham Ranjal" <gautham.shenoy@....com>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....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 v2 2/4] cpufreq: amd-pstate: Set a fallback policy based
 on preferred_profile

On Tue, Jun 20, 2023 at 11:18:30PM +0800, Limonciello, Mario wrote:
> 
> On 6/20/2023 10:06 AM, Huang Rui wrote:
> > On Tue, Jun 20, 2023 at 11:02:00PM +0800, Limonciello, Mario wrote:
> >> On 6/20/2023 9:58 AM, Huang Rui wrote:
> >>> On Thu, Jun 15, 2023 at 02:32:25PM +0800, Yuan, Perry wrote:
> >>>> From: Mario Limonciello <mario.limonciello@....com>
> >>>>
> >>>> If a user's configuration doesn't explicitly specify the cpufreq
> >>>> scaling governor then the code currently explicitly falls back to
> >>>> 'powersave'. This default is fine for notebooks and desktops, but
> >>> May I know if the processor is powerful desktop such as threadripper,
> >>> whether it will be default to 'performance' or 'powersave'?
> >> It's currently defaulting to 'powersave' for desktops and
> >> workstations.
> >>
> >> Do you think we should adopt performance for these?
> > Yes, I didn't see any different use cases here between server and
> > threadripper here. Or I missed anything?
> Workstations and Desktops usually have to go through energy
> consumption certifications.  Couldn't setting it to performance be
> inappropriate for those?

Hmm, that makes sense. Energy consumption certification is sufficient
reason.

> > Do we have a way to separate them?
> 
> If Threadripper identified as
> 
> 3 Workstation
> 
> I'd agree; but I'd think we're going to lump AM4/AM5 desktops
> along with Threadripper.  So should we still set all those to performance?
> 

If we don't have good way to separate them, we can set them to powersave at
this moment with your original patches. But I think we would better dig out
a method in future.

Please add my Acks for these series in next version.

Acked-by: Huang Rui <ray.huang@....com>

> >
> > Thanks,
> > Ray
> >
> >>> Thanks,
> >>> Ray
> >>>
> >>>> servers and undefined machines should default to 'performance'.
> >>>>
> >>>> Look at the 'preferred_profile' field from the FADT to set this
> >>>> policy accordingly.
> >>>>
> >>>> Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html#fixed-acpi-description-table-fadt
> >>>> Suggested-by: Wyes Karny <Wyes.Karny@....com>
> >>>> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
> >>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >>>> ---
> >>>>    drivers/cpufreq/amd-pstate.c | 7 +++++--
> >>>>    1 file changed, 5 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> >>>> index ddd346a239e0..c9d296ebf81e 100644
> >>>> --- a/drivers/cpufreq/amd-pstate.c
> >>>> +++ b/drivers/cpufreq/amd-pstate.c
> >>>> @@ -1102,10 +1102,13 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
> >>>>    	policy->max = policy->cpuinfo.max_freq;
> >>>>    
> >>>>    	/*
> >>>> -	 * Set the policy to powersave to provide a valid fallback value in case
> >>>> +	 * Set the policy to provide a valid fallback value in case
> >>>>    	 * the default cpufreq governor is neither powersave nor performance.
> >>>>    	 */
> >>>> -	policy->policy = CPUFREQ_POLICY_POWERSAVE;
> >>>> +	if (acpi_pm_profile_server() || acpi_pm_profile_undefined())
> >>>> +		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
> >>>> +	else
> >>>> +		policy->policy = CPUFREQ_POLICY_POWERSAVE;
> >>>>    
> >>>>    	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> >>>>    		ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
> >>>> -- 
> >>>> 2.34.1
> >>>>