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 10:02:00 -0500
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Huang Rui <ray.huang@....com>, "Yuan, Perry" <Perry.Yuan@....com>
Cc:     "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 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?

>
> 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
>>