linux-kernel - Re: [RESEND PATCH V2 2/9] cpufreq: amd_pstate: add module parameter to load amd pstate EPP driver

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Message-ID: <Y00koVkHD3ECCY7H@amd.com>
Date:   Mon, 17 Oct 2022 17:47:13 +0800
From:   Huang Rui <ray.huang@....com>
To:     "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>,
        "Limonciello, Mario" <Mario.Limonciello@....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: [RESEND PATCH V2 2/9] cpufreq: amd_pstate: add module parameter
 to load amd pstate EPP driver

On Tue, Oct 11, 2022 at 12:22:41AM +0800, Yuan, Perry wrote:
> The amd_pstate mode parameter will allow user to select which amd pstate
> working mode as booting mode, amd_pstate instance or amd_pstate_epp instance.
> 
> 1) amd_pstate instance is depending on the target operation mode.
> 2) amd_pstate_epp instance is depending on the set_policy operation mode.It
>    is also called active mode that AMD SMU has EPP algorithm to control the
>    CPU runtime frequency according to the EPP set value and workload.
> 

There is one concern here: how can the user know which kind of processor
supports the EPP function in hardware?

Thanks,
Ray

> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index f52b8f2fe529..2d28f458589c 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -63,6 +63,10 @@ module_param(shared_mem, bool, 0444);
>  MODULE_PARM_DESC(shared_mem,
>  		 "enable amd-pstate on processors with shared memory solution (false = disabled (default), true = enabled)");
>  
> +static bool epp = false;
> +module_param(epp, bool, 0444);
> +MODULE_PARM_DESC(epp, "Enable energy performance preference (EPP) control");
> +
>  static struct cpufreq_driver amd_pstate_driver;
>  
>  /**
> -- 
> 2.34.1
>