Re: [PATCH 6/7] cpufreq: amd_pstate: implement amd pstate cpu online and offline callback

["Limonciello, Mario" <mario.limonciello@amd.com>]

On 9/9/2022 11:45, Perry Yuan wrote:
> The patch adds online and offline driver callback to 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@amd.com>
> ---
>   drivers/cpufreq/amd-pstate.c | 93 +++++++++++++++++++++++++++++++++++-
>   1 file changed, 92 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index e71b06e20050..e63fed39f90c 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -111,7 +111,8 @@ struct amd_aperf_mperf {
>    * @cppc_cap1_cached: Cached value of the last CPPC Capabilities MSR
>    * @update_util: Cpufreq utility callback information
>    * @sample: the stored performance sample
> -
> + * @suspended:	Whether or not the driver has been suspended.
> + *
>    * The amd_cpudata is key private data for each CPU thread in AMD P-State, and
>    * represents all the attributes and goals that AMD P-State requests at runtime.
>    */
> @@ -151,6 +152,7 @@ struct amd_cpudata {
>   	u64	cppc_cap1_cached;
>   	struct	update_util_data update_util;
>   	struct	amd_aperf_mperf sample;
> +	bool suspended;
>   };
>   
>   /**
> @@ -1387,6 +1389,93 @@ 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);

As this driver uses pr_fmt, this doesn't need to be as verbose.  Look at 
my comments in patch 7/7 and you can adopt the same here.

> +
> +	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 (epp_enabled) {
> +		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(AMD_CPPC_EPP_POWERSAVE);
> +		cppc_set_perf(cpudata->cpu, &perf_ctrls);
> +	}
> +	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 (epp_enabled)
> +		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)
>   {
> @@ -1421,6 +1510,8 @@ 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,
>   };