Date:   Tue, 31 Jan 2023 17:45:00 +0000
From:   Wyes Karny <wyes.karny@amd.com>
To:     Mario Limonciello <mario.limonciello@amd.com>
Cc:     Rafael J Wysocki <rafael@kernel.org>,
        Huang Rui <ray.huang@amd.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Viresh Kumar <viresh.kumar@linaro.org>, Perry.Yuan@amd.com,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, Bagas Sanjaya <bagasdotme@gmail.com>,
        santosh.shukla@amd.com, Len Brown <lenb@kernel.org>,
        Robert Moore <robert.moore@intel.com>,
        Borislav Petkov <bp@alien8.de>,
        Ananth Narayan <ananth.narayan@amd.com>,
        gautham.shenoy@amd.com, Tor Vic <torvic9@mailbox.org>
Subject: Re: [PATCH v4 3/6] cpufreq: amd_pstate: Add guided autonomous mode
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On 31 Jan 07:37, Mario Limonciello wrote:
> On 1/30/23 23:21, Wyes Karny 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.
> > 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@amd.com>
> > ---
> >   .../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..0d8486325c9a 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
> > +			  tires to match the same performance level (if it is
> 
> s/tires/tries/
> 
> I don't think you need the () either in this sentence.
> 
> > +			  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 c5731fefcbef..48ab4684c3a5 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -267,7 +267,22 @@ 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);
> > @@ -344,12 +359,18 @@ 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 guv_flags)
> 
> You meant "gov_flags" not "guv_flags" right?
> 
> >   {
> >   	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) && (guv_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);
> > @@ -404,7 +425,7 @@ 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;
> > @@ -438,7 +459,8 @@ 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);
> >   }
> > @@ -1238,7 +1260,7 @@ 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");
> > @@ -1300,7 +1322,7 @@ 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 e9e291b7c2f9..85e980b8e0ac 100644
> > --- a/include/linux/amd-pstate.h
> > +++ b/include/linux/amd-pstate.h
> > @@ -92,6 +92,7 @@ enum amd_pstate_mode {
> >   	AMD_PSTATE_DISABLE = 0,
> >   	AMD_PSTATE_PASSIVE,
> >   	AMD_PSTATE_ACTIVE,
> > +	AMD_PSTATE_GUIDED,
> >   	AMD_PSTATE_MAX,
> >   };
> > @@ -99,6 +100,7 @@ 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,
> >   };
> 
> With two nits fixed
> 
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>

Thanks! I'll fix those.

>