linux-kernel - Re: [PATCH v11 06/11] cpufreq: amd-pstate: implement suspend and resume callbacks

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Date:   Thu, 19 Jan 2023 11:01:01 +0530
From:   Wyes Karny <wyes.karny@....com>
To:     Perry Yuan <perry.yuan@....com>
Cc:     Deepak.Sharma@....com, Nathan.Fontenot@....com,
        Alexander.Deucher@....com, Shimmer.Huang@....com,
        Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rafael.j.wysocki@...el.com,
        Mario.Limonciello@....com, viresh.kumar@...aro.org,
        ray.huang@....com
Subject: Re: [PATCH v11 06/11] cpufreq: amd-pstate: implement suspend and
 resume callbacks



On 1/18/2023 1:22 PM, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> add suspend and resume support for the AMD processors by amd_pstate_epp
> driver instance.
> 
> When the CPPC is suspended, EPP driver will set EPP profile to 'power'
> profile and set max/min perf to lowest perf value.
> When resume happens, it will restore the MSR registers with
> previous cached value.
> 
> Acked-by: Huang Rui <ray.huang@....com>
> Tested-by: Wyes Karny <wyes.karny@....com>
> Reviewed-by: Mario Limonciello <Mario.Limonciello@....com>
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>

Reviewed-by: <wyes.karny@....com>

> ---
>  drivers/cpufreq/amd-pstate.c | 40 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 1472a6382b29..9e1bee060597 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1045,6 +1045,44 @@ static int amd_pstate_epp_verify_policy(struct cpufreq_policy_data *policy)
>  	return 0;
>  }
>  
> +static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +	int ret;
> +
> +	/* avoid suspending when EPP is not enabled */
> +	if (cppc_state != AMD_PSTATE_ACTIVE)
> +		return 0;
> +
> +	/* set this flag to avoid setting core offline*/
> +	cpudata->suspended = true;
> +
> +	/* disable CPPC in lowlevel firmware */
> +	ret = amd_pstate_enable(false);
> +	if (ret)
> +		pr_err("failed to suspend, return %d\n", ret);
> +
> +	return 0;
> +}
> +
> +static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata = policy->driver_data;
> +
> +	if (cpudata->suspended) {
> +		mutex_lock(&amd_pstate_limits_lock);
> +
> +		/* enable amd pstate from suspend state*/
> +		amd_pstate_epp_reenable(cpudata);
> +
> +		mutex_unlock(&amd_pstate_limits_lock);
> +
> +		cpudata->suspended = false;
> +	}
> +
> +	return 0;
> +}
> +
>  static struct cpufreq_driver amd_pstate_driver = {
>  	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
>  	.verify		= amd_pstate_verify,
> @@ -1066,6 +1104,8 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
>  	.exit		= amd_pstate_epp_cpu_exit,
>  	.offline	= amd_pstate_epp_cpu_offline,
>  	.online		= amd_pstate_epp_cpu_online,
> +	.suspend	= amd_pstate_epp_suspend,
> +	.resume		= amd_pstate_epp_resume,
>  	.name		= "amd_pstate_epp",
>  	.attr		= amd_pstate_epp_attr,
>  };

-- 
Thanks & Regards,
Wyes