linux-kernel - Re: [PATCH v3 04/13] cpufreq: amd-pstate: prefetch cppc_req_cached value in amd_pstate_cpu

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Date:   Wed, 13 Jul 2022 10:57:08 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Perry Yuan <Perry.Yuan@....com>
Cc:     rafael.j.wysocki@...el.com, Ray.Huang@....com,
        Deepak.Sharma@....com, Mario.Limonciello@....com,
        Nathan.Fontenot@....com, Alexander.Deucher@....com,
        Jinzhou.Su@....com, Xinmei.Huang@....com, Xiaojian.Du@....com,
        Li.Meng@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v3 04/13] cpufreq: amd-pstate: prefetch cppc_req_cached
 value in amd_pstate_cpu_init()

On 12-07-22, 11:40, Perry Yuan wrote:
> This cppc_req_cached valued should be prefetched during
> amd_pstate_cpu_init call period, then the amd_pstate_update() will get
> correct cached value before updating the perf to change the cpu perf
> level.

You are doing more than this in the patch, either mention all the
stuff with reasoning or split into two patches.

> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 43e6df9f67f6..e4904da54541 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -547,12 +547,17 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
>  	cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq;
>  
>  	policy->driver_data = cpudata;
> +	if (!shared_mem) {

This is a new change, which the commit log doesn't talk about.

> +		ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_HW_CTL, &value);
> +		if (ret)
> +			return ret;
> +		WRITE_ONCE(cpudata->cppc_hw_conf_cached, value);
>  
> -	ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_HW_CTL, &value);
> -	if (ret)
> -		return ret;
> -	WRITE_ONCE(cpudata->cppc_hw_conf_cached, value);
> -
> +		ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
> +		if (ret)
> +			return ret;
> +		WRITE_ONCE(cpudata->cppc_req_cached, value);
> +	}
>  	amd_pstate_boost_init(cpudata);
>  
>  	return 0;
> -- 
> 2.25.1

-- 
viresh