linux-kernel - Re: [PATCH v2 1/5] cpufreq/amd-pstate: Add dynamic energy performance preference

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Message-ID: <8e87fa8c-5254-46d5-a853-46e8c31cbe0e@amd.com>
Date: Wed, 12 Mar 2025 17:46:34 +0530
From: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
To: Mario Limonciello <superm1@...nel.org>,
 "Gautham R . Shenoy" <gautham.shenoy@....com>,
 Perry Yuan <perry.yuan@....com>
Cc: "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
 <linux-kernel@...r.kernel.org>,
 "open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>,
 Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v2 1/5] cpufreq/amd-pstate: Add dynamic energy performance
 preference

On 3/4/2025 8:53 PM, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
> 
> Dynamic energy performance preference will change the EPP profile
> based on whether the machine is running on AC or DC power.
> 
> A notification chain from the power supply core is used to adjust
> EPP values on plug in or plug out events.
> 
> For non-server systems:
>     * the default EPP for AC mode is `performance`.
>     * the default EPP for DC mode is `balance_performance`.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
> v1->v2:
>  * Change defaults to performance (AC) and balance_performance (DC)
>  * Default Kconfig to disabled for now
>  * Rebase on latest branch
> ---
>  Documentation/admin-guide/pm/amd-pstate.rst |  18 ++-
>  drivers/cpufreq/Kconfig.x86                 |  12 ++
>  drivers/cpufreq/amd-pstate.c                | 129 ++++++++++++++++++--
>  drivers/cpufreq/amd-pstate.h                |   5 +-
>  4 files changed, 155 insertions(+), 9 deletions(-)
> 
[Snip]
> @@ -1556,6 +1667,10 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>  	if (!policy->cpuinfo.max_freq)
>  		return -ENODEV;
>  
> +	/* policy can't be changed to performance policy while dynamic epp is enabled */
> +	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE && cpudata->dynamic_epp)
> +		return -EBUSY;

We might need to tweak this condition, because if we enable "CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP" in config
and boot with "amd_pstate=active" it lands here (cpufreq_online()->amd_pstate_epp_set_policy()) driver init fails 
as the default governor is performance. 

> +
>  	cpudata->policy = policy->policy;
>  
>  	ret = amd_pstate_epp_update_limit(policy);
> diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
> index fbe1c08d3f061..6882876f895de 100644
> --- a/drivers/cpufreq/amd-pstate.h
> +++ b/drivers/cpufreq/amd-pstate.h
> @@ -104,7 +104,10 @@ struct amd_cpudata {
>  	/* EPP feature related attributes*/
>  	u32	policy;
>  	bool	suspended;
> -	u8	epp_default;
> +	u8	epp_default_ac;
> +	u8	epp_default_dc;
> +	bool	dynamic_epp;
> +	struct notifier_block power_nb;
>  };
>  
>  /*