linux-kernel - Re: [PATCH v4 1/2] cpufreq: intel_pstate: Rearrange the storing of new EPP values

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Date:   Wed, 29 Jul 2020 18:31:07 -0700
From:   Francisco Jerez <currojerez@...eup.net>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     Linux Documentation <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Doug Smythies <dsmythies@...us.net>
Subject: Re: [PATCH v4 1/2] cpufreq: intel_pstate: Rearrange the storing of new EPP values

"Rafael J. Wysocki" <rjw@...ysocki.net> writes:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Move the locking away from intel_pstate_set_energy_pref_index()
> into its only caller and drop the (now redundant) return_pref label
> from it.
>
> Also move the "raw" EPP value check into the caller of that function,
> so as to do it before acquiring the mutex, and reduce code duplication
> related to the "raw" EPP values processing somewhat.
>
> No intentional functional impact.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Francisco Jerez <currojerez@...eup.net>

> ---
>
> v2 -> v3:
>
>    * Fix error handling in intel_pstate_set_energy_pref_index() and
>      rebase.
>
> v3 -> v4: No changes
>
> ---
>  drivers/cpufreq/intel_pstate.c |   35 +++++++++++++++--------------------
>  1 file changed, 15 insertions(+), 20 deletions(-)
>
> Index: linux-pm/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> +++ linux-pm/drivers/cpufreq/intel_pstate.c
> @@ -649,28 +649,18 @@ static int intel_pstate_set_energy_pref_
>  	if (!pref_index)
>  		epp = cpu_data->epp_default;
>  
> -	mutex_lock(&intel_pstate_limits_lock);
> -
>  	if (boot_cpu_has(X86_FEATURE_HWP_EPP)) {
>  		u64 value;
>  
>  		ret = rdmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, &value);
>  		if (ret)
> -			goto return_pref;
> +			return ret;
>  
>  		value &= ~GENMASK_ULL(31, 24);
>  
> -		if (use_raw) {
> -			if (raw_epp > 255) {
> -				ret = -EINVAL;
> -				goto return_pref;
> -			}
> -			value |= (u64)raw_epp << 24;
> -			ret = wrmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, value);
> -			goto return_pref;
> -		}
> -
> -		if (epp == -EINVAL)
> +		if (use_raw)
> +			epp = raw_epp;
> +		else if (epp == -EINVAL)
>  			epp = epp_values[pref_index - 1];
>  
>  		value |= (u64)epp << 24;
> @@ -680,8 +670,6 @@ static int intel_pstate_set_energy_pref_
>  			epp = (pref_index - 1) << 2;
>  		ret = intel_pstate_set_epb(cpu_data->cpu, epp);
>  	}
> -return_pref:
> -	mutex_unlock(&intel_pstate_limits_lock);
>  
>  	return ret;
>  }
> @@ -708,8 +696,8 @@ static ssize_t store_energy_performance_
>  	struct cpudata *cpu_data = all_cpu_data[policy->cpu];
>  	char str_preference[21];
>  	bool raw = false;
> +	ssize_t ret;
>  	u32 epp = 0;
> -	int ret;
>  
>  	ret = sscanf(buf, "%20s", str_preference);
>  	if (ret != 1)
> @@ -724,14 +712,21 @@ static ssize_t store_energy_performance_
>  		if (ret)
>  			return ret;
>  
> +		if (epp > 255)
> +			return -EINVAL;
> +
>  		raw = true;
>  	}
>  
> +	mutex_lock(&intel_pstate_limits_lock);
> +
>  	ret = intel_pstate_set_energy_pref_index(cpu_data, ret, raw, epp);
> -	if (ret)
> -		return ret;
> +	if (!ret)
> +		ret = count;
>  
> -	return count;
> +	mutex_unlock(&intel_pstate_limits_lock);
> +
> +	return ret;
>  }
>  
>  static ssize_t show_energy_performance_preference(


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