Re: [PATCH v6 3/6] cpufreq: amd_pstate: Add guided autonomous mode

[Huang Rui]

On Tue, Feb 07, 2023 at 01:21:54AM +0800, Karny, Wyes wrote:
> From ACPI spec below 3 modes for CPPC can be defined:
> 1. Non autonomous: OS scaling governor specifies operating frequency/
>    performance level through `Desired Performance` register and platform
> follows that.
> 2. Guided autonomous: OS scaling governor specifies min and max
>    frequencies/ performance levels through `Minimum Performance` and
> `Maximum Performance` register, and platform can autonomously select an
> operating frequency in this range.

I believe the processors which are not sensitive to power consumption can
use this mode. Because this way can have better performance than "non
autonomous" mode. :-)

> 3. Fully autonomous: OS only hints (via EPP) to platform for the required
>    energy performance preference for the workload and platform autonomously
> scales the frequency.
> 
> Currently (1) is supported by amd_pstate as passive mode, and (3) is
> implemented by EPP support. This change is to support (2).
> 
> In guided autonomous mode the min_perf is based on the input from the
> scaling governor. For example, in case of schedutil this value depends
> on the current utilization. And max_perf is set to max capacity.
> 
> To activate guided auto mode ``amd_pstate=guided`` command line
> parameter has to be passed in the kernel.
> 
> Signed-off-by: Wyes Karny <wyes.karny@xxxxxxx>
> Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>

Wyes, could you still use prefix "cpufreq: amd-pstate:" as the subject to
align the previous patches? Because it's easy to sort out all amd-pstate
patches for us.

Acked-by: Huang Rui <ray.huang@xxxxxxx>

> ---
>  .../admin-guide/kernel-parameters.txt         | 15 +++++---
>  drivers/cpufreq/amd-pstate.c                  | 34 +++++++++++++++----
>  include/linux/amd-pstate.h                    |  2 ++
>  3 files changed, 40 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e3618dfdb36a..56d5c189e458 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -7015,11 +7015,11 @@
>  			  Do not enable amd_pstate as the default
>  			  scaling driver for the supported processors
>  			passive
> -			  Use amd_pstate as a scaling driver, driver requests a
> -			  desired performance on this abstract scale and the power
> -			  management firmware translates the requests into actual
> -			  hardware states (core frequency, data fabric and memory
> -			  clocks etc.)
> +			  Use amd_pstate with passive mode as a scaling driver.
> +			  In this mode autonomous selection is disabled.
> +			  Driver requests a desired performance level and platform
> +			  tries to match the same performance level if it is
> +			  satisfied by guaranteed performance level.
>  			active
>  			  Use amd_pstate_epp driver instance as the scaling driver,
>  			  driver provides a hint to the hardware if software wants
> @@ -7027,3 +7027,8 @@
>  			  to the CPPC firmware. then CPPC power algorithm will
>  			  calculate the runtime workload and adjust the realtime cores
>  			  frequency.
> +			guided
> +			  Activate guided autonomous mode. Driver requests minimum and
> +			  maximum performance level and the platform autonomously
> +			  selects a performance level in this range and appropriate
> +			  to the current workload.
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 168a28bed6ee..6582c922ad3a 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -308,7 +308,22 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
>  		   cppc_perf.lowest_nonlinear_perf);
>  	WRITE_ONCE(cpudata->lowest_perf, cppc_perf.lowest_perf);
>  
> -	return 0;
> +	if (cppc_state == AMD_PSTATE_ACTIVE)
> +		return 0;
> +
> +	ret = cppc_get_auto_sel_caps(cpudata->cpu, &cppc_perf);
> +	if (ret) {
> +		pr_warn("failed to get auto_sel, ret: %d\n", ret);
> +		return 0;
> +	}
> +
> +	ret = cppc_set_auto_sel(cpudata->cpu,
> +			(cppc_state == AMD_PSTATE_PASSIVE) ? 0 : 1);
> +
> +	if (ret)
> +		pr_warn("failed to set auto_sel, ret: %d\n", ret);
> +
> +	return ret;
>  }
>  
>  DEFINE_STATIC_CALL(amd_pstate_init_perf, pstate_init_perf);
> @@ -385,12 +400,18 @@ static inline bool amd_pstate_sample(struct amd_cpudata *cpudata)
>  }
>  
>  static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> -			      u32 des_perf, u32 max_perf, bool fast_switch)
> +			      u32 des_perf, u32 max_perf, bool fast_switch, int gov_flags)
>  {
>  	u64 prev = READ_ONCE(cpudata->cppc_req_cached);
>  	u64 value = prev;
>  
>  	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
> +
> +	if ((cppc_state == AMD_PSTATE_GUIDED) && (gov_flags & CPUFREQ_GOV_DYNAMIC_SWITCHING)) {
> +		min_perf = des_perf;
> +		des_perf = 0;
> +	}
> +
>  	value &= ~AMD_CPPC_MIN_PERF(~0L);
>  	value |= AMD_CPPC_MIN_PERF(min_perf);
>  
> @@ -445,7 +466,7 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
>  
>  	cpufreq_freq_transition_begin(policy, &freqs);
>  	amd_pstate_update(cpudata, min_perf, des_perf,
> -			  max_perf, false);
> +			  max_perf, false, policy->governor->flags);
>  	cpufreq_freq_transition_end(policy, &freqs, false);
>  
>  	return 0;
> @@ -479,7 +500,8 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>  	if (max_perf < min_perf)
>  		max_perf = min_perf;
>  
> -	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true);
> +	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, true,
> +			policy->governor->flags);
>  	cpufreq_cpu_put(policy);
>  }
>  
> @@ -1279,7 +1301,7 @@ static int __init amd_pstate_init(void)
>  	/* capability check */
>  	if (boot_cpu_has(X86_FEATURE_CPPC)) {
>  		pr_debug("AMD CPPC MSR based functionality is supported\n");
> -		if (cppc_state == AMD_PSTATE_PASSIVE)
> +		if (cppc_state != AMD_PSTATE_ACTIVE)
>  			current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
>  	} else {
>  		pr_debug("AMD CPPC shared memory based functionality is supported\n");
> @@ -1341,7 +1363,7 @@ static int __init amd_pstate_param(char *str)
>  		if (cppc_state == AMD_PSTATE_ACTIVE)
>  			current_pstate_driver = &amd_pstate_epp_driver;
>  
> -		if (cppc_state == AMD_PSTATE_PASSIVE)
> +		if (cppc_state == AMD_PSTATE_PASSIVE || cppc_state == AMD_PSTATE_GUIDED)
>  			current_pstate_driver = &amd_pstate_driver;
>  
>  		return 0;
> diff --git a/include/linux/amd-pstate.h b/include/linux/amd-pstate.h
> index f5f22418e64b..c10ebf8c42e6 100644
> --- a/include/linux/amd-pstate.h
> +++ b/include/linux/amd-pstate.h
> @@ -97,6 +97,7 @@ enum amd_pstate_mode {
>  	AMD_PSTATE_DISABLE = 0,
>  	AMD_PSTATE_PASSIVE,
>  	AMD_PSTATE_ACTIVE,
> +	AMD_PSTATE_GUIDED,
>  	AMD_PSTATE_MAX,
>  };
>  
> @@ -104,6 +105,7 @@ static const char * const amd_pstate_mode_string[] = {
>  	[AMD_PSTATE_DISABLE]     = "disable",
>  	[AMD_PSTATE_PASSIVE]     = "passive",
>  	[AMD_PSTATE_ACTIVE]      = "active",
> +	[AMD_PSTATE_GUIDED]      = "guided",
>  	NULL,
>  };
>  #endif /* _LINUX_AMD_PSTATE_H */
> -- 
> 2.34.1
>