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SubjectRe: [PATCH v5 06/22] cpufreq: amd: introduce a new amd pstate driver to support future processors
On Fri, Dec 17, 2021 at 01:59:35AM +0800, Rafael J. Wysocki wrote:
> On Tue, Nov 30, 2021 at 1:37 PM Huang Rui <ray.huang@amd.com> wrote:
> >
> > amd-pstate is the AMD CPU performance scaling driver that introduces a
> > new CPU frequency control mechanism on AMD Zen based CPU series in Linux
> > kernel. 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_CPPC 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 adjust to the most efficiency frequency according to
> > the kernel scheduler loading.
> >
> > Please check the detailed CPU feature and MSR register description in
> > Processor Programming Reference (PPR) for AMD Family 19h Model 51h,
> > Revision A1 Processors:
> >
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amd.com%2Fsystem%2Ffiles%2FTechDocs%2F56569-A1-PUB.zip&amp;data=04%7C01%7Cray.huang%40amd.com%7C271b150291c64c7e3db808d9c0bdd9b0%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637752744522397473%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=VlOP2McSZlC11NJSJoVB74alfUqpdyDmoaAgT8Vl2Qc%3D&amp;reserved=0
> >
> > Signed-off-by: Huang Rui <ray.huang@amd.com>
> > ---
> > drivers/cpufreq/Kconfig.x86 | 17 ++
> > drivers/cpufreq/Makefile | 1 +
> > drivers/cpufreq/amd-pstate.c | 398 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 416 insertions(+)
> > create mode 100644 drivers/cpufreq/amd-pstate.c
> >
> > diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
> > index 92701a18bdd9..21837eb1698b 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
> > + tristate "AMD Processor P-State driver"
> > + depends on X86
> > + select ACPI_PROCESSOR if ACPI
> > + select ACPI_CPPC_LIB if X86_64 && ACPI
> > + select CPU_FREQ_GOV_SCHEDUTIL if SMP
> > + help
> > + This driver adds a CPUFreq driver which utilizes a fine grain
> > + processor performance frequency control range instead of legacy
> > + performance levels. This driver supports the AMD processors with
> > + _CPC object in the SBIOS.
>
> Well, _CPC needs to be present in the ACPI tables of the system.

Yes, will modify the words.

>
> > +
> > + For details, take a look at:
> > + <file:Documentation/admin-guide/pm/amd-pstate.rst>.
> > +
> > + 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..20ffbc30118f
> > --- /dev/null
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -0,0 +1,398 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * amd-pstate.c - AMD Processor P-state Frequency Driver
> > + *
> > + * Copyright (C) 2021 Advanced Micro Devices, Inc. All Rights Reserved.
> > + *
> > + * Author: Huang Rui <ray.huang@amd.com>
>
> Given the lack of other documentation, it would be nice to provide at
> least a brief description of the driver here.

Fine, will add the description in V6.

>
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/smp.h>
> > +#include <linux/sched.h>
> > +#include <linux/cpufreq.h>
> > +#include <linux/compiler.h>
> > +#include <linux/dmi.h>
> > +#include <linux/slab.h>
> > +#include <linux/acpi.h>
> > +#include <linux/io.h>
> > +#include <linux/delay.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/static_call.h>
> > +
> > +#include <acpi/processor.h>
> > +#include <acpi/cppc_acpi.h>
> > +
> > +#include <asm/msr.h>
> > +#include <asm/processor.h>
> > +#include <asm/cpufeature.h>
> > +#include <asm/cpu_device_id.h>
> > +
> > +#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;
> > +};
>
> Please describe the fields of this structure, preferably in a kerneldoc comment.

OK.

>
> > +
> > +static inline int pstate_enable(bool enable)
> > +{
> > + return wrmsrl_safe(MSR_AMD_CPPC_ENABLE, enable);
> > +}
> > +
> > +DEFINE_STATIC_CALL(amd_pstate_enable, pstate_enable);
>
> Why do you need a static call here?
>
> It doesn't get updated anywhere below.

Ah, the update behavior is defined in the following patch 8 (shared memory
support). Sorry to make you confused.

>
> > +
> > +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());
> > +
> > + 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);
>
> And same here.
>
> > +
> > +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);
>
> Same here.
>
> > +
> > +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 max_perf, min_perf, des_perf, cap_perf;
> > +
> > + if (!cpudata->max_freq)
> > + return -ENODEV;
> > +
> > + cap_perf = READ_ONCE(cpudata->highest_perf);
> > + min_perf = READ_ONCE(cpudata->lowest_nonlinear_perf);
> > + max_perf = cap_perf;
> > +
> > + freqs.old = policy->cur;
> > + freqs.new = target_freq;
> > +
> > + des_perf = DIV_ROUND_CLOSEST(target_freq * cap_perf,
> > + cpudata->max_freq);
> > +
> > + cpufreq_freq_transition_begin(policy, &freqs);
> > + amd_pstate_update(cpudata, min_perf, des_perf,
> > + 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;
> > +
> > + int ret = cppc_get_perf_caps(cpudata->cpu, &cppc_perf);
> > + if (ret)
> > + return ret;
> > +
> > + /* Switch to khz */
> > + return cppc_perf.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;
> > + 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 = policy->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;
>
> The freq_qos requests below are never updated in this file. What are they for?

The freq_qos requests will be updated while we set boost disabled or
enabled in patch 10. Sorry to make you confused again. Should I move the
freq_qos requests implementation into patch 10 as well?

Thanks,
Ray

>
> > +
> > + 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;
> > +
> > +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("the _CPC object is not present in SBIOS\n");
> > + 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_CPPC)) {
> > + pr_debug("AMD CPPC MSR based functionality is not supported\n");
> > + return -ENODEV;
> > + }
> > +
> > + /* enable amd pstate feature */
> > + ret = amd_pstate_enable(true);
> > + if (ret) {
> > + pr_err("failed to enable amd-pstate with return %d\n", ret);
> > + return ret;
> > + }
> > +
> > + ret = cpufreq_register_driver(&amd_pstate_driver);
> > + if (ret)
> > + pr_err("failed to register amd_pstate_driver with return %d\n",
> > + ret);
> > +
> > + return ret;
> > +}
> > +
> > +static void __exit amd_pstate_exit(void)
> > +{
> > + cpufreq_unregister_driver(&amd_pstate_driver);
> > +
> > + amd_pstate_enable(false);
> > +}
> > +
> > +module_init(amd_pstate_init);
> > +module_exit(amd_pstate_exit);
> > +
> > +MODULE_AUTHOR("Huang Rui <ray.huang@amd.com>");
> > +MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.25.1
> >

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