linux-kernel - Re: [PATCH v2 07/14] cpufreq: amd_pstate: map desired perf into pstate scope for powersave governor

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Date:   Mon, 11 Jul 2022 14:33:48 -0500
From:   Nathan Fontenot <nafonten@....com>
To:     Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
        viresh.kumar@...aro.org, Ray.Huang@....com
Cc:     Deepak.Sharma@....com, Mario.Limonciello@....com,
        Nathan.Fontenot@....com, Alexander.Deucher@....com,
        Jinzhou.Su@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
        Li.Meng@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/14] cpufreq: amd_pstate: map desired perf into
 pstate scope for powersave governor

On 7/9/22 09:19, Perry Yuan wrote:
> The patch will fix the invalid desired perf value for powersave
> governor. This issue is found when testing on one AMD EPYC system, the
> actual des_perf is smaller than the min_perf value, that is invalid
> value. because the min_perf is the lowest_perf system can support in
> idle state.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 7c51f4125263..8a2b6ad9b8c0 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -265,6 +265,7 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>  	u64 prev = READ_ONCE(cpudata->cppc_req_cached);
>  	u64 value = prev;
>  
> +	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);

You should also update amd_pstate_adjust_perf() to remove the clamp_t() call now
that it is done here.

-Nathan

>  	value &= ~AMD_CPPC_MIN_PERF(~0L);
>  	value |= AMD_CPPC_MIN_PERF(min_perf);
>