linux-kernel - Re: [PATCH 2/7] cpufreq: amd_pstate: add module parameter to load amd pstate EPP driver

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Date:   Fri, 9 Sep 2022 13:49:41 -0500
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
        ray.huang@....com, viresh.kumar@...aro.org
Cc:     Deepak.Sharma@....com, Nathan.Fontenot@....com,
        Alexander.Deucher@....com, Jinzhou.Su@....com,
        Shimmer.Huang@....com, Xiaojian.Du@....com, Li.Meng@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] cpufreq: amd_pstate: add module parameter to load amd
 pstate EPP driver

On 9/9/2022 11:45, Perry Yuan 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.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>   drivers/cpufreq/amd-pstate.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index a2463f785322..451295284a26 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -58,6 +58,12 @@ 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_enabled = true;
> +module_param(epp_enabled, bool, 0444);
> +MODULE_PARM_DESC(epp_enabled,
> +                "load amd_pstate or amd_pstate_epp (true = amd_pstate_epp driver instance (default), false = amd_pstate driver instance)");
> +

If you're operating in EPP mode or not the kernel module is still 
'amd-pstate'.  So to a user I think this is a pretty confusing 
designation.

I would propose the following instead:

 > +static bool epp = true;
 > +module_param(epp, bool, 0444);
 > +MODULE_PARM_DESC(epp,
 > +                "Enable energy performance preference (EPP) control");

> +
>   static struct cpufreq_driver amd_pstate_driver;
>   
>   /**