linux-kernel - Re: [PATCH 2/7] cpufreq: amd-pstate: initialize new core precision boost state

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Message-ID: <a673c90b-40c2-4b62-9239-530ced5a9140@amd.com>
Date: Fri, 26 Jan 2024 10:01:01 -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 2/7] cpufreq: amd-pstate: initialize new core precision
 boost state

On 1/26/2024 02:08, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> Add gloal global_params to represent current CPU Performance Boost(cpb)
> state for cpu frequency scaling, both active and passive modes all can
> support CPU cores frequency boosting control which is based on the BIOS
> setting, while BIOS turn on the "Core Performance Boost", it will
> allow OS control each core highest perf limitation from OS side.
> 
> If core performance boost is disabled while a core is in a boosted P-state,
> the core transitions to the highest performance non-boosted P-state,
> that is the same as the nominal frequency limit.
> 
> Issue: https://bugzilla.kernel.org/show_bug.cgi?id=217931

Rather than "Issue" this should be "Closes:", and the tag should come 
right after the Reported-by tag.

> Reported-by: Artem S. Tashkinov" <aros@....com>
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>   drivers/cpufreq/amd-pstate.c | 46 ++++++++++++++++++++++++++++--------
>   include/linux/amd-pstate.h   |  1 -
>   2 files changed, 36 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 8f308f56ade6..0dc9124140d4 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -65,6 +65,19 @@ static struct cpufreq_driver amd_pstate_epp_driver;
>   static int cppc_state = AMD_PSTATE_UNDEFINED;
>   static bool cppc_enabled;
>   
> +/**
> + * struct global_params - Global parameters, mostly tunable via sysfs.
> + * @cpb_boost:		Whether or not to use boost CPU P-states.
> + * @cpb_supported:	Whether or not CPU boost P-states are available
> + *			based on the MSR_K7_HWCR bit[25] state
> + */
> +struct global_params {
> +	bool cpb_boost;
> +	bool cpb_supported;
> +};
> +
> +static struct global_params global;
> +
>   /*
>    * AMD Energy Preference Performance (EPP)
>    * The EPP is used in the CCLK DPM controller to drive
> @@ -632,18 +645,27 @@ static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
>   	return lowest_nonlinear_freq * 1000;
>   }
>   
> -static void amd_pstate_boost_init(struct amd_cpudata *cpudata)
> +static int amd_pstate_boost_init(struct amd_cpudata *cpudata)
>   {
> -	u32 highest_perf, nominal_perf;
> +	u64 boost_state, boost_val;
> +	int ret;
>   
> -	highest_perf = READ_ONCE(cpudata->highest_perf);
> -	nominal_perf = READ_ONCE(cpudata->nominal_perf);
> +	ret = rdmsrl_on_cpu(cpudata->cpu, MSR_K7_HWCR, &boost_val);
> +	if (ret) {
> +		pr_err_once("failed to read initial CPU boost state!\n");
> +		return ret;
> +	}
>   
> -	if (highest_perf <= nominal_perf)
> -		return;
> +	boost_state = (boost_val >> 25) & 0x1;
> +	if (!boost_state) {
> +		global.cpb_supported = true;
> +		global.cpb_boost = true;
> +	} else {
> +		global.cpb_supported = false;
> +		global.cpb_boost = false;
> +	}

Seems like a lot of lines and an extra variable that could be simplified 
down to just:

global.cpb_supported = (boost_val >> 25) & 0x1;
global.cpb_boost = global.cpb_supported;

>   
> -	cpudata->boost_supported = true;
> -	current_pstate_driver->boost_enabled = true;
> +	return ret;
>   }
>   
>   static void amd_perf_ctl_reset(unsigned int cpu)
> @@ -676,6 +698,9 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>   	if (ret)
>   		goto free_cpudata1;
>   
> +	/* initialize cpu cores boot state */
> +	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);
> @@ -725,7 +750,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>   
>   	policy->driver_data = cpudata;
>   
> -	amd_pstate_boost_init(cpudata);
>   	if (!current_pstate_driver->adjust_perf)
>   		current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
>   
> @@ -1093,6 +1117,9 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>   	if (ret)
>   		goto free_cpudata1;
>   
> +	/* initialize cpu cores boot state */
> +	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);
> @@ -1143,7 +1170,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
>   			return ret;
>   		WRITE_ONCE(cpudata->cppc_cap1_cached, value);
>   	}
> -	amd_pstate_boost_init(cpudata);
>   
>   	return 0;
>   
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index 446394f84606..66d939a344b1 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -80,7 +80,6 @@ struct amd_cpudata {
>   	struct amd_aperf_mperf prev;
>   
>   	u64	freq;
> -	bool	boost_supported;
>   
>   	/* EPP feature related attributes*/
>   	s16	epp_policy;