linux-kernel - Re: [PATCH 3/6] cpufreq:amd-pstate: initialize nominal

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Message-ID: <67d61b66-4e3b-4b59-af3e-151c2af937bc@amd.com>
Date: Wed, 31 Jan 2024 15:47:29 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com
Cc: Alexander.Deucher@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
 Li.Meng@....com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] cpufreq:amd-pstate: initialize nominal_freq of each
 cpudata

On 1/31/2024 02:50, Perry Yuan wrote:
> Optimizes the process of retrieving the nominal frequency by utilizing
> 'cpudata->nominal_freq' instead of repeatedly accessing the cppc_acpi interface.
> 
> To enhance efficiency and reduce the CPU load, shifted to using
> 'cpudata->nominal_freq'. It allows for the nominal frequency to be accessed
> directly from the cached data in 'cpudata' of each CPU.
> It will also slightly reduce the frequency change latency while using pstate
> driver passive mode.
> 
> Signed-off-by: Perry Yuan <perry.yuan@....com>
Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> ---
>   drivers/cpufreq/amd-pstate.c | 26 ++++++++++++++------------
>   1 file changed, 14 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 9291a22bd3cc..db7b36afdce2 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -600,7 +600,7 @@ static int amd_get_max_freq(struct amd_cpudata *cpudata)
>   	if (ret)
>   		return ret;
>   
> -	nominal_freq = cppc_perf.nominal_freq;
> +	nominal_freq = READ_ONCE(cpudata->nominal_freq);
>   	nominal_perf = READ_ONCE(cpudata->nominal_perf);
>   	max_perf = READ_ONCE(cpudata->highest_perf);
>   
> @@ -639,7 +639,7 @@ static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
>   	if (ret)
>   		return ret;
>   
> -	nominal_freq = cppc_perf.nominal_freq;
> +	nominal_freq = READ_ONCE(cpudata->nominal_freq);
>   	nominal_perf = READ_ONCE(cpudata->nominal_perf);
>   
>   	lowest_nonlinear_perf = cppc_perf.lowest_nonlinear_perf;
> @@ -712,13 +712,15 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>   	amd_pstate_boost_init(cpudata);
>   
>   	min_freq = amd_get_min_freq(cpudata);
> -	max_freq = amd_get_max_freq(cpudata);
>   	nominal_freq = amd_get_nominal_freq(cpudata);
> +	cpudata->nominal_freq = nominal_freq;
> +	max_freq = amd_get_max_freq(cpudata);
>   	lowest_nonlinear_freq = amd_get_lowest_nonlinear_freq(cpudata);
>   
> -	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq) {
> -		dev_err(dev, "min_freq(%d) or max_freq(%d) value is incorrect\n",
> -			min_freq, max_freq);
> +	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq || nominal_freq == 0) {
> +		dev_err(dev, "min_freq(%d) or max_freq(%d) or nominal_freq(%d)	\
> +			value is incorrect\n",	\
> +			min_freq, max_freq, nominal_freq);
>   		ret = -EINVAL;
>   		goto free_cpudata1;
>   	}
> @@ -755,7 +757,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>   	/* Initial processor data capability frequencies */
>   	cpudata->max_freq = max_freq;
>   	cpudata->min_freq = min_freq;
> -	cpudata->nominal_freq = nominal_freq;
>   	cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;
>   
>   	policy->driver_data = cpudata;
> @@ -1266,12 +1267,14 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>   	amd_pstate_boost_init(cpudata);
>   
>   	min_freq = amd_get_min_freq(cpudata);
> -	max_freq = amd_get_max_freq(cpudata);
>   	nominal_freq = amd_get_nominal_freq(cpudata);
> +	cpudata->nominal_freq = nominal_freq;
> +	max_freq = amd_get_max_freq(cpudata);
>   	lowest_nonlinear_freq = amd_get_lowest_nonlinear_freq(cpudata);
> -	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq) {
> -		dev_err(dev, "min_freq(%d) or max_freq(%d) value is incorrect\n",
> -				min_freq, max_freq);
> +	if (min_freq < 0 || max_freq < 0 || min_freq > max_freq || nominal_freq == 0) {
> +		dev_err(dev, "min_freq(%d) or max_freq(%d) or nominal_freq(%d)	\
> +				value is incorrect\n",	\
> +				min_freq, max_freq, nominal_freq);
>   		ret = -EINVAL;
>   		goto free_cpudata1;
>   	}
> @@ -1284,7 +1287,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>   	/* Initial processor data capability frequencies */
>   	cpudata->max_freq = max_freq;
>   	cpudata->min_freq = min_freq;
> -	cpudata->nominal_freq = nominal_freq;
>   	cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;
>   
>   	policy->driver_data = cpudata;