linux-kernel - Re: [PATCH 4/7] cpufreq: amd_pstate: add AMD pstate EPP support for shared memory type processor

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Message-ID: <a21bdd7d-3ade-4a54-1a7f-42831ce8e83a@amd.com>
Date:   Thu, 15 Sep 2022 11:24:06 -0500
From:   Nathan Fontenot <nathan.fontenot@....com>
To:     Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
        ray.huang@....com, viresh.kumar@...aro.org
Cc:     Deepak.Sharma@....com, Mario.Limonciello@....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 4/7] cpufreq: amd_pstate: add AMD pstate EPP support for
 shared memory type processor

On 9/9/22 11:45, Perry Yuan wrote:
> Add Energy Performance Preference support for AMD SOCs which only
> support the shared memory interface that implemented on Zen2 and Zen3
> processors, because this type CPU has no MSR supported, it will use
> ACPI PCC channel to enable EPP and reset desired perf to be zero.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 451295284a26..fff298744a8e 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -133,12 +133,24 @@ static inline int pstate_enable(bool enable)
>  
>  static int cppc_enable(bool enable)
>  {
> +	struct cppc_perf_ctrls perf_ctrls;
>  	int cpu, ret = 0;
>  
>  	for_each_present_cpu(cpu) {
>  		ret = cppc_set_enable(cpu, enable);
>  		if (ret)
>  			return ret;
> +
> +	/* Enable active mode for EPP */
> +	ret = cppc_set_auto_epp(cpu, enable);
> +	if (ret)
> +		return ret;
> +
> +	/* Set zero to desired perf to enable EPP control*/
> +	perf_ctrls.desired_perf = 0;
> +	ret = cppc_set_perf(cpu, &perf_ctrls);
> +	if (ret)
> +		return ret;

Shouldn't this entire block be indented one additional tab over since its
part of the for_each_present_cpu() loop?

-Nathan

>  	}
>  
>  	return ret;