linux-kernel - Re: [PATCH 3/5] cpufreq/amd-pstate: Refactor amd_pstate_epp_reenable() and amd_pstate_epp

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Message-ID: <Z1KFDDFl3L7bHS9k@BLRRASHENOY1.amd.com>
Date: Fri, 6 Dec 2024 10:31:00 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Cc: mario.limonciello@....com, perry.yuan@....com, rafael@...nel.org,
	viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] cpufreq/amd-pstate: Refactor
 amd_pstate_epp_reenable() and amd_pstate_epp_offline()

On Wed, Dec 04, 2024 at 02:48:40PM +0000, Dhananjay Ugwekar wrote:
> Replace similar code chunks with amd_pstate_update_perf() and
> amd_pstate_set_epp() function calls.
> 
> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 36 +++++++-----------------------------
>  1 file changed, 7 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index a1b2393cef22..a38be7727c9d 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1630,25 +1630,17 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>  
>  static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
>  {
> -	struct cppc_perf_ctrls perf_ctrls;
> -	u64 value, max_perf;
> +	u64 max_perf;
>  	int ret;
>  
>  	ret = amd_pstate_cppc_enable(true);
>  	if (ret)
>  		pr_err("failed to enable amd pstate during resume, return %d\n", ret);
>  
> -	value = READ_ONCE(cpudata->cppc_req_cached);
>  	max_perf = READ_ONCE(cpudata->highest_perf);
>  
> -	if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> -		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> -	} else {
> -		perf_ctrls.max_perf = max_perf;
> -		cppc_set_perf(cpudata->cpu, &perf_ctrls);
> -		perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(cpudata->epp_cached);
> -		cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> -	}
> +	amd_pstate_update_perf(cpudata, 0, 0, max_perf, false);
> +	amd_pstate_set_epp(cpudata, cpudata->epp_cached);

This will cause two MSR writes on MSR based systems.

But then, we don't expect the amd_pstate_epp_reenable() and
amd_pstate_epp_offline() to be called often. Hence it should be ok.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>

--
Thanks and Regards
gautham.




>  }
>  
>  static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
> @@ -1668,7 +1660,6 @@ static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
>  static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
>  {
>  	struct amd_cpudata *cpudata = policy->driver_data;
> -	struct cppc_perf_ctrls perf_ctrls;
>  	int min_perf;
>  	u64 value;
>  
> @@ -1676,23 +1667,10 @@ static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
>  	value = READ_ONCE(cpudata->cppc_req_cached);
>  
>  	mutex_lock(&amd_pstate_limits_lock);
> -	if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
> -		cpudata->epp_policy = CPUFREQ_POLICY_UNKNOWN;
> -
> -		/* Set max perf same as min perf */
> -		value &= ~AMD_CPPC_MAX_PERF(~0L);
> -		value |= AMD_CPPC_MAX_PERF(min_perf);
> -		value &= ~AMD_CPPC_MIN_PERF(~0L);
> -		value |= AMD_CPPC_MIN_PERF(min_perf);
> -		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> -	} else {
> -		perf_ctrls.desired_perf = 0;
> -		perf_ctrls.min_perf = min_perf;
> -		perf_ctrls.max_perf = min_perf;
> -		cppc_set_perf(cpudata->cpu, &perf_ctrls);
> -		perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(HWP_EPP_BALANCE_POWERSAVE);
> -		cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> -	}
> +
> +	amd_pstate_update_perf(cpudata, min_perf, 0, min_perf, false);
> +	amd_pstate_set_epp(cpudata, AMD_CPPC_EPP_BALANCE_POWERSAVE);
> +
>  	mutex_unlock(&amd_pstate_limits_lock);
>  }
>  
> -- 
> 2.34.1
>