Date: Wed, 07 Feb 2024 15:45:20 +0100
From: Oleksandr Natalenko <oleksandr@...alenko.name>
To: rafael.j.wysocki@...el.com, Mario.Limonciello@....com,
 viresh.kumar@...aro.org, Ray.Huang@....com, gautham.shenoy@....com,
 Borislav.Petkov@....com, Perry Yuan <perry.yuan@....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 v3 1/7] cpufreq: amd-pstate: initialize new core precision boost
 state

On středa 7. února 2024 10:21:52 CET 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.
> 
> Reported-by: Artem S. Tashkinov" <aros@....com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 49 ++++++++++++------------------------
>  include/linux/amd-pstate.h   | 14 +++++++++++
>  2 files changed, 30 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 08e112444c27..3772f71f525f 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -67,6 +67,7 @@ static struct cpufreq_driver amd_pstate_epp_driver;
>  static int cppc_state = AMD_PSTATE_UNDEFINED;
>  static bool cppc_enabled;
>  static bool amd_pstate_prefcore = true;
> +struct global_params global;

Doesn't this require `EXPORT_SYMBOL_GPL(global)` then? Otherwise with v6.8 I get this:

```
ERROR: modpost: "global" [drivers/cpufreq/amd-pstate-ut.ko] undefined!
```

If so, I'd pretty mush rename this to be less generic, say, `amd_pstate_global_params_struct` for the struct name itself and `amd_pstate_global_params` for the actual variable name.

>  
>  /*
>   * AMD Energy Preference Performance (EPP)
> @@ -669,43 +670,21 @@ static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata)
>  	return lowest_nonlinear_freq * 1000;
>  }
>  
> -static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
> +static int amd_pstate_boost_init(struct amd_cpudata *cpudata)
>  {
> -	struct amd_cpudata *cpudata = policy->driver_data;
> +	u64 boost_val;
>  	int ret;
>  
> -	if (!cpudata->boost_supported) {
> -		pr_err("Boost mode is not supported by this processor or SBIOS\n");
> -		return -EINVAL;
> -	}
> -
> -	if (state)
> -		policy->cpuinfo.max_freq = cpudata->max_freq;
> -	else
> -		policy->cpuinfo.max_freq = cpudata->nominal_freq;
> -
> -	policy->max = policy->cpuinfo.max_freq;
> -
> -	ret = freq_qos_update_request(&cpudata->req[1],
> -				      policy->cpuinfo.max_freq);
> -	if (ret < 0)
> +	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;
> +	}
>  
> -	return 0;
> -}
> -
> -static void amd_pstate_boost_init(struct amd_cpudata *cpudata)
> -{
> -	u32 highest_perf, nominal_perf;
> -
> -	highest_perf = READ_ONCE(cpudata->highest_perf);
> -	nominal_perf = READ_ONCE(cpudata->nominal_perf);
> -
> -	if (highest_perf <= nominal_perf)
> -		return;
> +	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)
> @@ -848,6 +827,9 @@ 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);
> @@ -899,7 +881,6 @@ 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;
>  
> @@ -1310,6 +1291,9 @@ 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);
> @@ -1360,7 +1344,6 @@ 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 d21838835abd..465e9295a60c 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -124,4 +124,18 @@ static const char * const amd_pstate_mode_string[] = {
>  	[AMD_PSTATE_GUIDED]      = "guided",
>  	NULL,
>  };
> +
> +/**
> + * 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;
> +};
> +
> +extern struct global_params global;
> +
>  #endif /* _LINUX_AMD_PSTATE_H */
> 


-- 
Oleksandr Natalenko (post-factum)
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