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The new mechanism is based on Collaborative processor > performance control (CPPC) which is finer grain frequency management > than legacy ACPI hardware P-States. Current AMD CPU platforms are using > the ACPI P-states driver to manage CPU frequency and clocks with > switching only in 3 P-states. AMD P-States is to replace the ACPI > P-states controls, allows a flexible, low-latency interface for the > Linux kernel to directly communicate the performance hints to hardware. > > "amd-pstate" leverages the Linux kernel governors such as *schedutil*, > *ondemand*, etc. to manage the performance hints which are provided by CPPC > hardware functionality. The first version for amd-pstate is to support one > of the Zen3 processors, and we will support more in future after we verify > the hardware and SBIOS functionalities. > > There are two types of hardware implementations for amd-pstate: one is full > MSR support and another is shared memory support. It can use > X86_FEATURE_AMD_CPPC_EXT feature flag to distinguish the different types. > > Using the new AMD P-States method + kernel governors (*schedutil*, > *ondemand*, ...) to manage the frequency update is the most appropriate > bridge between AMD Zen based hardware processor and Linux kernel, the > processor is able to ajust to the most efficiency frequency according to > the kernel scheduler loading. > > Performance Per Watt (PPW) Caculation: > > The PPW caculation is referred by below paper: > https://software.intel.com/content/dam/develop/external/us/en/documents/performance-per-what-paper.pdf > > Below formula is referred from below spec to measure the PPW: > > (F / t) / P = F * t / (t * E) = F / E, > > "F" is the number of frames per second. > "P" is power measurd in watts. > "E" is energy measured in joules. > > We use the RAPL interface with "perf" tool to get the energy data of the > package power. > > The data comparsions between amd-pstate and acpi-freq module are tested on > AMD Cezanne processor: > > 1) TBench CPU benchmark: > > +---------------------------------------------------------------------+ > | | > | TBench (Performance Per Watt) | > | Higher is better | > +-------------------+------------------------+------------------------+ > | | Performance Per Watt | Performance Per Watt | > | Kernel Module | (Schedutil) | (Ondemand) | > | | Unit: MB / (s * J) | Unit: MB / (s * J) | > +-------------------+------------------------+------------------------+ > | | | | > | acpi-cpufreq | 3.022 | 2.969 | > | | | | > +-------------------+------------------------+------------------------+ > | | | | > | amd-pstate | 3.131 | 3.284 | > | | | | > +-------------------+------------------------+------------------------+ > > 2) Gitsource CPU benchmark: > > +---------------------------------------------------------------------+ > | | > | Gitsource (Performance Per Watt) | > | Higher is better | > +-------------------+------------------------+------------------------+ > | | Performance Per Watt | Performance Per Watt | > | Kernel Module | (Schedutil) | (Ondemand) | > | | Unit: 1 / (s * J) | Unit: 1 / (s * J) | > +-------------------+------------------------+------------------------+ > | | | | > | acpi-cpufreq | 3.42172E-07 | 2.74508E-07 | > | | | | > +-------------------+------------------------+------------------------+ > | | | | > | amd-pstate | 4.09141E-07 | 3.47610E-07 | > | | | | > +-------------------+------------------------+------------------------+ > > 3) Speedometer 2.0 CPU benchmark: > > +---------------------------------------------------------------------+ > | | > | Speedometer 2.0 (Performance Per Watt) | > | Higher is better | > +-------------------+------------------------+------------------------+ > | | Performance Per Watt | Performance Per Watt | > | Kernel Module | (Schedutil) | (Ondemand) | > | | Unit: 1 / (s * J) | Unit: 1 / (s * J) | > +-------------------+------------------------+------------------------+ > | | | | > | acpi-cpufreq | 0.116111767 | 0.110321664 | > | | | | > +-------------------+------------------------+------------------------+ > | | | | > | amd-pstate | 0.115825281 | 0.122024299 | > | | | | > +-------------------+------------------------+------------------------+ > > According to above average data, we can see this solution has shown better > performance per watt scaling on mobile CPU benchmarks in most of cases. > > Signed-off-by: Huang Rui > --- > drivers/cpufreq/Kconfig.x86 | 17 ++ > drivers/cpufreq/Makefile | 1 + > drivers/cpufreq/amd-pstate.c | 413 +++++++++++++++++++++++++++++++++++ > 3 files changed, 431 insertions(+) > create mode 100644 drivers/cpufreq/amd-pstate.c > > diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86 > index 92701a18bdd9..2e798b2c0bdb 100644 > --- a/drivers/cpufreq/Kconfig.x86 > +++ b/drivers/cpufreq/Kconfig.x86 > @@ -34,6 +34,23 @@ config X86_PCC_CPUFREQ > > If in doubt, say N. > > +config X86_AMD_PSTATE > + bool "AMD Processor P-State driver" > + depends on X86 > + select ACPI_PROCESSOR if ACPI > + select ACPI_CPPC_LIB if X86_64 && ACPI && SCHED_MC_PRIO > + select CPU_FREQ_GOV_SCHEDUTIL if SMP > + help > + This driver adds a CPUFreq driver which utilizes a fine grain > + processor performance freqency control range instead of legacy > + performance levels. This driver supports the AMD processors with > + _CPC object in the SBIOS. > + > + For details, take a look at: > + . > + > + If in doubt, say N. > + > config X86_ACPI_CPUFREQ > tristate "ACPI Processor P-States driver" > depends on ACPI_PROCESSOR > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile > index 48ee5859030c..c8d307010922 100644 > --- a/drivers/cpufreq/Makefile > +++ b/drivers/cpufreq/Makefile > @@ -25,6 +25,7 @@ obj-$(CONFIG_CPUFREQ_DT_PLATDEV) += cpufreq-dt-platdev.o > # speedstep-* is preferred over p4-clockmod. > > obj-$(CONFIG_X86_ACPI_CPUFREQ) += acpi-cpufreq.o > +obj-$(CONFIG_X86_AMD_PSTATE) += amd-pstate.o > obj-$(CONFIG_X86_POWERNOW_K8) += powernow-k8.o > obj-$(CONFIG_X86_PCC_CPUFREQ) += pcc-cpufreq.o > obj-$(CONFIG_X86_POWERNOW_K6) += powernow-k6.o > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c > new file mode 100644 > index 000000000000..a400861c7fdc > --- /dev/null > +++ b/drivers/cpufreq/amd-pstate.c > @@ -0,0 +1,413 @@ > +/* > + * amd-pstate.c - AMD Processor P-state Frequency Driver > + * > + * Copyright (C) 2021 Advanced Micro Devices, Inc. All Rights Reserved. > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; either version 2 > + * of the License, or (at your option) any later version. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License along with > + * this program; if not, write to the Free Software > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. > + * > + * Author: Huang Rui > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include > +#include > + > +#include > +#include > +#include > +#include > + > +#define AMD_PSTATE_TRANSITION_LATENCY 0x20000 > +#define AMD_PSTATE_TRANSITION_DELAY 500 > + > +static struct cpufreq_driver amd_pstate_driver; > + > +struct amd_cpudata { > + int cpu; > + > + struct freq_qos_request req[2]; > + > + u64 cppc_req_cached; > + > + u32 highest_perf; > + u32 nominal_perf; > + u32 lowest_nonlinear_perf; > + u32 lowest_perf; > + > + u32 max_freq; > + u32 min_freq; > + u32 nominal_freq; > + u32 lowest_nonlinear_freq; > +}; > + > +static inline int pstate_enable(bool enable) > +{ > + return wrmsrl_safe(MSR_AMD_CPPC_ENABLE, enable ? 1 : 0); > +} > + > +DEFINE_STATIC_CALL(amd_pstate_enable, pstate_enable); > + > +static inline int amd_pstate_enable(bool enable) > +{ > + return static_call(amd_pstate_enable)(enable); > +} > + > +static int pstate_init_perf(struct amd_cpudata *cpudata) > +{ > + u64 cap1; > + > + int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1, > + &cap1); > + if (ret) > + return ret; > + > + /* > + * TODO: Introduce AMD specific power feature. > + * > + * CPPC entry doesn't indicate the highest performance in some ASICs. > + */ > + WRITE_ONCE(cpudata->highest_perf, amd_get_highest_perf()); Wouldn't it be better to default to CAP1_HIGHEST_PERF(cap1) and quirk the ones that don't work instead? > + > + WRITE_ONCE(cpudata->nominal_perf, CAP1_NOMINAL_PERF(cap1)); > + WRITE_ONCE(cpudata->lowest_nonlinear_perf, CAP1_LOWNONLIN_PERF(cap1)); > + WRITE_ONCE(cpudata->lowest_perf, CAP1_LOWEST_PERF(cap1)); > + > + return 0; > +} > + > +DEFINE_STATIC_CALL(amd_pstate_init_perf, pstate_init_perf); > + > +static inline int amd_pstate_init_perf(struct amd_cpudata *cpudata) > +{ > + return static_call(amd_pstate_init_perf)(cpudata); > +} > + > +static void pstate_update_perf(struct amd_cpudata *cpudata, u32 min_perf, > + u32 des_perf, u32 max_perf, bool fast_switch) > +{ > + if (fast_switch) > + wrmsrl(MSR_AMD_CPPC_REQ, READ_ONCE(cpudata->cppc_req_cached)); > + else > + wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, > + READ_ONCE(cpudata->cppc_req_cached)); > +} > + > +DEFINE_STATIC_CALL(amd_pstate_update_perf, pstate_update_perf); > + > +static inline void amd_pstate_update_perf(struct amd_cpudata *cpudata, > + u32 min_perf, u32 des_perf, > + u32 max_perf, bool fast_switch) > +{ > + static_call(amd_pstate_update_perf)(cpudata, min_perf, des_perf, > + max_perf, fast_switch); > +} > + > +static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf, > + u32 des_perf, u32 max_perf, bool fast_switch) > +{ > + u64 prev = READ_ONCE(cpudata->cppc_req_cached); > + u64 value = prev; > + > + value &= ~REQ_MIN_PERF(~0L); > + value |= REQ_MIN_PERF(min_perf); > + > + value &= ~REQ_DES_PERF(~0L); > + value |= REQ_DES_PERF(des_perf); > + > + value &= ~REQ_MAX_PERF(~0L); > + value |= REQ_MAX_PERF(max_perf); > + > + if (value == prev) > + return; > + > + WRITE_ONCE(cpudata->cppc_req_cached, value); > + > + amd_pstate_update_perf(cpudata, min_perf, des_perf, > + max_perf, fast_switch); > +} > + > +static int amd_pstate_verify(struct cpufreq_policy_data *policy) > +{ > + cpufreq_verify_within_cpu_limits(policy); > + > + return 0; > +} > + > +static int amd_pstate_target(struct cpufreq_policy *policy, > + unsigned int target_freq, > + unsigned int relation) > +{ > + struct cpufreq_freqs freqs; > + struct amd_cpudata *cpudata = policy->driver_data; > + unsigned long amd_max_perf, amd_min_perf, amd_des_perf, > + amd_cap_perf; > + > + if (!cpudata->max_freq) > + return -ENODEV; > + > + amd_cap_perf = READ_ONCE(cpudata->highest_perf); > + amd_min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf); > + amd_max_perf = amd_cap_perf; > + > + freqs.old = policy->cur; > + freqs.new = target_freq; > + > + amd_des_perf = DIV_ROUND_CLOSEST(target_freq * amd_cap_perf, > + cpudata->max_freq); > + > + cpufreq_freq_transition_begin(policy, &freqs); > + amd_pstate_update(cpudata, amd_min_perf, amd_des_perf, > + amd_max_perf, false); > + cpufreq_freq_transition_end(policy, &freqs, false); > + > + return 0; > +} > + > +static int amd_get_min_freq(struct amd_cpudata *cpudata) > +{ > + struct cppc_perf_caps cppc_perf; > + > + int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf); > + if (ret) > + return ret; > + > + /* Switch to khz */ > + return cppc_perf.lowest_freq * 1000; > +} > + > +static int amd_get_max_freq(struct amd_cpudata *cpudata) > +{ > + struct cppc_perf_caps cppc_perf; > + u32 max_perf, max_freq, nominal_freq, nominal_perf; > + u64 boost_ratio; > + > + int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf); > + if (ret) > + return ret; > + > + nominal_freq = cppc_perf.nominal_freq; > + nominal_perf = READ_ONCE(cpudata->nominal_perf); > + max_perf = READ_ONCE(cpudata->highest_perf); > + > + boost_ratio = div_u64(max_perf << SCHED_CAPACITY_SHIFT, > + nominal_perf); > + > + max_freq = nominal_freq * boost_ratio >> SCHED_CAPACITY_SHIFT; > + > + /* Switch to khz */ > + return max_freq * 1000; > +} > + > +static int amd_get_nominal_freq(struct amd_cpudata *cpudata) > +{ > + struct cppc_perf_caps cppc_perf; > + u32 nominal_freq; > + > + int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf); > + if (ret) > + return ret; > + > + nominal_freq = cppc_perf.nominal_freq; > + > + /* Switch to khz */ > + return nominal_freq * 1000; > +} > + > +static int amd_get_lowest_nonlinear_freq(struct amd_cpudata *cpudata) > +{ > + struct cppc_perf_caps cppc_perf; > + u32 lowest_nonlinear_freq, lowest_nonlinear_perf, > + nominal_freq, nominal_perf; > + u64 lowest_nonlinear_ratio; > + > + int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf); > + if (ret) > + return ret; > + > + nominal_freq = cppc_perf.nominal_freq; > + nominal_perf = READ_ONCE(cpudata->nominal_perf); > + > + lowest_nonlinear_perf = cppc_perf.lowest_nonlinear_perf; > + > + lowest_nonlinear_ratio = div_u64(lowest_nonlinear_perf << > + SCHED_CAPACITY_SHIFT, nominal_perf); > + > + lowest_nonlinear_freq = nominal_freq * lowest_nonlinear_ratio >> SCHED_CAPACITY_SHIFT; > + > + /* Switch to khz */ > + return lowest_nonlinear_freq * 1000; > +} > + > +static int amd_pstate_cpu_init(struct cpufreq_policy *policy) > +{ > + int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret; > + unsigned int cpu = policy->cpu; > + struct device *dev; > + struct amd_cpudata *cpudata; > + > + dev = get_cpu_device(policy->cpu); > + if (!dev) > + return -ENODEV; > + > + cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL); > + if (!cpudata) > + return -ENOMEM; > + > + cpudata->cpu = cpu; > + > + ret = amd_pstate_init_perf(cpudata); > + if (ret) > + goto free_cpudata1; > + > + min_freq = amd_get_min_freq(cpudata); > + max_freq = amd_get_max_freq(cpudata); > + nominal_freq = amd_get_nominal_freq(cpudata); > + lowest_nonlinear_freq = amd_get_lowest_nonlinear_freq(cpudata); > + > + if (min_freq < 0 || max_freq < 0 || min_freq > max_freq) { > + dev_err(dev, "min_freq(%d) or max_freq(%d) value is incorrect\n", > + min_freq, max_freq); > + ret = -EINVAL; > + goto free_cpudata1; > + } > + > + policy->cpuinfo.transition_latency = AMD_PSTATE_TRANSITION_LATENCY; > + policy->transition_delay_us = AMD_PSTATE_TRANSITION_DELAY; > + > + policy->min = min_freq; > + policy->max = max_freq; > + > + policy->cpuinfo.min_freq = min_freq; > + policy->cpuinfo.max_freq = max_freq; > + > + /* It will be updated by governor */ > + policy->cur = policy->cpuinfo.min_freq; > + > + ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0], > + FREQ_QOS_MIN, policy->cpuinfo.min_freq); > + if (ret < 0) { > + dev_err(dev, "Failed to add min-freq constraint (%d)\n", ret); > + goto free_cpudata1; > + } > + > + ret = freq_qos_add_request(&policy->constraints, &cpudata->req[1], > + FREQ_QOS_MAX, policy->cpuinfo.max_freq); > + if (ret < 0) { > + dev_err(dev, "Failed to add max-freq constraint (%d)\n", ret); > + goto free_cpudata2; > + } > + > + /* Initial processor data capability frequencies */ > + cpudata->max_freq = max_freq; > + cpudata->min_freq = min_freq; > + cpudata->nominal_freq = nominal_freq; > + cpudata->lowest_nonlinear_freq = lowest_nonlinear_freq; > + > + policy->driver_data = cpudata; > + > + return 0; > + > + freq_qos_remove_request(&cpudata->req[1]); > +free_cpudata2: > + freq_qos_remove_request(&cpudata->req[0]); > +free_cpudata1: > + kfree(cpudata); > + return ret; > +} > + > +static int amd_pstate_cpu_exit(struct cpufreq_policy *policy) > +{ > + struct amd_cpudata *cpudata; > + > + cpudata = policy->driver_data; > + > + freq_qos_remove_request(&cpudata->req[1]); > + freq_qos_remove_request(&cpudata->req[0]); > + kfree(cpudata); > + > + return 0; > +} > + > +static struct cpufreq_driver amd_pstate_driver = { > + .flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS, > + .verify = amd_pstate_verify, > + .target = amd_pstate_target, > + .init = amd_pstate_cpu_init, > + .exit = amd_pstate_cpu_exit, > + .name = "amd-pstate", > +}; > + > +static int __init amd_pstate_init(void) > +{ > + int ret; > + > + if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) > + return -ENODEV; > + > + if (!acpi_cpc_valid()) { > + pr_debug("%s, the _CPC object is not present in SBIOS\n", > + __func__); > + return -ENODEV; > + } > + > + /* don't keep reloading if cpufreq_driver exists */ > + if (cpufreq_get_current_driver()) > + return -EEXIST; > + > + /* capability check */ > + if (!boot_cpu_has(X86_FEATURE_AMD_CPPC)) { > + pr_debug("%s, AMD CPPC MSR based functionality is not supported\n", > + __func__); > + return -ENODEV; > + } > + > + /* enable amd pstate feature */ > + ret = amd_pstate_enable(true); > + if (ret) { > + pr_err("%s, failed to enable amd-pstate with return %d\n", > + __func__, ret); > + return ret; > + } > + > + ret = cpufreq_register_driver(&amd_pstate_driver); > + if (ret) { > + pr_err("%s, return %d\n", __func__, ret); > + return ret; > + } > + > + return 0; > +} > + > +device_initcall(amd_pstate_init); > + > +MODULE_AUTHOR("Huang Rui "); > +MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver"); > +MODULE_LICENSE("GPL"); >