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Date:   Fri, 9 Dec 2022 15:34:28 +0530
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Subject: Re: [PATCH 1/4] cpufreq: amd_pstate: Add guided autonomous mode
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To:     Huang Rui <ray.huang@amd.com>
Cc:     "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        "Limonciello, Mario" <Mario.Limonciello@amd.com>,
        "Yuan, Perry" <Perry.Yuan@amd.com>,
        "Narayan, Ananth" <Ananth.Narayan@amd.com>,
        "Shenoy, Gautham Ranjal" <gautham.shenoy@amd.com>
References: <20221207154648.233759-1-wyes.karny@amd.com>
 <20221207154648.233759-2-wyes.karny@amd.com> <Y5LnB+zUjy7aJmOr@amd.com>
From:   Wyes Karny <wyes.karny@amd.com>
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Hi Ray,

On 12/9/2022 1:13 PM, Huang Rui wrote:
> On Wed, Dec 07, 2022 at 11:46:45PM +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 PMFW
>> follows that.
>> 2. Guided autonomous: OS scaling governor specifies min and max
>>    frequencies/ performance levels through `Minimum Performance` and
>> `Maximum Performance` register, and PMFW can autonomously select an
>> operating frequency in this range.
>> 3. Fully autonomous: OS only hints (via EPP) to PMFW for the required
>>    energy performance preference for the workload and PMFW 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@amd.com>
>> ---
>>  .../admin-guide/kernel-parameters.txt         |  4 ++
>>  drivers/cpufreq/amd-pstate.c                  | 60 +++++++++++++++----
>>  2 files changed, 53 insertions(+), 11 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 42af9ca0127e..75e57afba77e 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -6970,3 +6970,7 @@
>>  			  management firmware translates the requests into actual
>>  			  hardware states (core frequency, data fabric and memory
>>  			  clocks etc.)
>> +			guided
>> +			  Activate guided autonomous mode. Driver requests minimum
>> +			  performance and maximum performance and the PMFW autonomously
>> +			  selects frequencies in this range.
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 204e39006dda..05e4003a77ee 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -50,6 +50,20 @@
>>  #define AMD_PSTATE_TRANSITION_LATENCY	20000
>>  #define AMD_PSTATE_TRANSITION_DELAY	1000
>>  
>> +enum amd_pstate_mode {
>> +	CPPC_DISABLE = 0,
>> +	CPPC_PASSIVE,
>> +	CPPC_GUIDED,
>> +	CPPC_MODE_MAX,
>> +};
>> +
>> +static const char * const amd_pstate_mode_string[] = {
>> +	[CPPC_DISABLE]     = "disable",
>> +	[CPPC_PASSIVE]     = "passive",
>> +	[CPPC_GUIDED]      = "guided",
>> +	NULL,
>> +};
>> +
>>  /*
>>   * TODO: We need more time to fine tune processors with shared memory solution
>>   * with community together.
>> @@ -60,7 +74,18 @@
>>   * module parameter to be able to enable it manually for debugging.
>>   */
>>  static struct cpufreq_driver amd_pstate_driver;
>> -static int cppc_load __initdata;
>> +static int cppc_state = CPPC_DISABLE;
>> +
>> +static inline int get_mode_idx_from_str(const char *str, size_t size)
>> +{
>> +	int i = 0;
>> +
>> +	for (; i < CPPC_MODE_MAX; ++i) {
>> +		if (!strncmp(str, amd_pstate_mode_string[i], size))
>> +			return i;
>> +	}
>> +	return -EINVAL;
>> +}
>>  
>>  static inline int pstate_enable(bool enable)
>>  {
>> @@ -212,12 +237,18 @@ 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 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 == CPPC_GUIDED && flags & CPUFREQ_GOV_DYNAMIC_SWITCHING) {
>> +		min_perf = des_perf;
>> +		des_perf = 0;
>> +	}
> 
> Since we would like to modify the min_perf on share memory processors as
> well. The current cppc_set_perf() in cppc_acpi doesn't provide the MIN/MAX
> values. Could you please add the max_perf/min_perf in cppc_acpi.c as well?
> Then the APIs will be available on the share memory processors like Rome.

Sure. Thanks for pointing this out.

> 
> Thanks,
> Ray
> 
>> +
>>  	value &= ~AMD_CPPC_MIN_PERF(~0L);
>>  	value |= AMD_CPPC_MIN_PERF(min_perf);
>>  
>> @@ -272,7 +303,7 @@ 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;
>> @@ -306,7 +337,8 @@ 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);
>>  }
>>  
>>  static int amd_get_min_freq(struct amd_cpudata *cpudata)
>> @@ -627,7 +659,7 @@ static int __init amd_pstate_init(void)
>>  	 * enable the amd_pstate passive mode driver explicitly
>>  	 * with amd_pstate=passive in kernel command line
>>  	 */
>> -	if (!cppc_load) {
>> +	if (cppc_state == CPPC_DISABLE) {
>>  		pr_debug("driver load is disabled, boot with amd_pstate=passive to enable this\n");
>>  		return -ENODEV;
>>  	}
>> @@ -670,16 +702,22 @@ device_initcall(amd_pstate_init);
>>  
>>  static int __init amd_pstate_param(char *str)
>>  {
>> +	int size, mode_idx;
>> +
>>  	if (!str)
>>  		return -EINVAL;
>>  
>> -	if (!strcmp(str, "disable")) {
>> -		cppc_load = 0;
>> -		pr_info("driver is explicitly disabled\n");
>> -	} else if (!strcmp(str, "passive"))
>> -		cppc_load = 1;
>> +	size = strlen(str);
>> +	mode_idx = get_mode_idx_from_str(str, size);
>>  
>> -	return 0;
>> +	if (mode_idx >= CPPC_DISABLE && mode_idx < CPPC_MODE_MAX) {
>> +		cppc_state = mode_idx;
>> +		if (cppc_state == CPPC_DISABLE)
>> +			pr_info("driver is explicitly disabled\n");
>> +		return 0;
>> +	}
>> +
>> +	return -EINVAL;
>>  }
>>  early_param("amd_pstate", amd_pstate_param);
>>  
>> -- 
>> 2.34.1
>>

-- 
Thanks & Regards,
Wyes