Re: [PATCH v7 06/13] cpufreq: amd-pstate: implement amd pstate cpu online and offline callback

[Huang Rui]

On Thu, Dec 08, 2022 at 07:18:45PM +0800, Yuan, Perry wrote:
> From: Perry Yuan <Perry.Yuan@xxxxxxx>
> 
> Adds online and offline driver callback support to allow cpu cores go
> offline and help to restore the previous working states when core goes
> back online later for EPP driver mode.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> ---
>  drivers/cpufreq/amd-pstate.c | 89 ++++++++++++++++++++++++++++++++++++
>  include/linux/amd-pstate.h   |  1 +
>  2 files changed, 90 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 0a521be1be8a..412accab7bda 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -1186,6 +1186,93 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
>  	return 0;
>  }
>  
> +static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
> +{
> +	struct cppc_perf_ctrls perf_ctrls;
> +	u64 value, max_perf;
> +	int ret;
> +
> +	ret = amd_pstate_enable(true);
> +	if (ret)
> +		pr_err("failed to enable amd pstate during resume, return %d\n", ret);
> +
> +	value = READ_ONCE(cpudata->cppc_req_cached);
> +	max_perf = READ_ONCE(cpudata->highest_perf);
> +
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +	} else {
> +		perf_ctrls.max_perf = max_perf;
> +		perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(cpudata->epp_cached);
> +		cppc_set_perf(cpudata->cpu, &perf_ctrls);
> +	}
> +}
> +
> +static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
> +
> +	pr_debug("AMD CPU Core %d going online\n", cpudata->cpu);
> +
> +	if (cppc_active) {
> +		amd_pstate_epp_reenable(cpudata);
> +		cpudata->suspended = false;
> +	}
> +
> +	return 0;
> +}
> +
> +static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
> +	struct cppc_perf_ctrls perf_ctrls;
> +	int min_perf;
> +	u64 value;
> +
> +	min_perf = READ_ONCE(cpudata->lowest_perf);
> +	value = READ_ONCE(cpudata->cppc_req_cached);
> +
> +	mutex_lock(&amd_pstate_limits_lock);
> +	if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +		cpudata->epp_policy = CPUFREQ_POLICY_UNKNOWN;
> +
> +		/* Set max perf same as min perf */
> +		value &= ~AMD_CPPC_MAX_PERF(~0L);
> +		value |= AMD_CPPC_MAX_PERF(min_perf);
> +		value &= ~AMD_CPPC_MIN_PERF(~0L);
> +		value |= AMD_CPPC_MIN_PERF(min_perf);
> +		wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> +	} else {
> +		perf_ctrls.desired_perf = 0;
> +		perf_ctrls.max_perf = min_perf;
> +		perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(HWP_EPP_POWERSAVE);
> +		cppc_set_perf(cpudata->cpu, &perf_ctrls);
> +	}

Could you double confirm whether these registers will be cleared or
modified while the CPU cores enter/exit online/offline? I remember Joe gave
a test before, the register value will be saved even it gets back to
idle/offline.

Thanks,
Ray

> +	mutex_unlock(&amd_pstate_limits_lock);
> +}
> +
> +static int amd_pstate_cpu_offline(struct cpufreq_policy *policy)
> +{
> +	struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
> +
> +	pr_debug("AMD CPU Core %d going offline\n", cpudata->cpu);
> +
> +	if (cpudata->suspended)
> +		return 0;
> +
> +	if (cppc_active)
> +		amd_pstate_epp_offline(policy);
> +
> +	return 0;
> +}
> +
> +static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
> +{
> +	amd_pstate_clear_update_util_hook(policy->cpu);
> +
> +	return amd_pstate_cpu_offline(policy);
> +}
> +
>  static void amd_pstate_verify_cpu_policy(struct amd_cpudata *cpudata,
>  					   struct cpufreq_policy_data *policy)
>  {
> @@ -1220,6 +1307,8 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
>  	.init		= amd_pstate_epp_cpu_init,
>  	.exit		= amd_pstate_epp_cpu_exit,
>  	.update_limits	= amd_pstate_epp_update_limits,
> +	.offline	= amd_pstate_epp_cpu_offline,
> +	.online		= amd_pstate_epp_cpu_online,
>  	.name		= "amd_pstate_epp",
>  	.attr		= amd_pstate_epp_attr,
>  };
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index 888af62040f1..3dd26a3d104c 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -99,6 +99,7 @@ struct amd_cpudata {
>  	u64	cppc_cap1_cached;
>  	struct	update_util_data update_util;
>  	struct	amd_aperf_mperf sample;
> +	bool suspended;
>  };
>  
>  /**
> -- 
> 2.34.1
>