// SPDX-License-Identifier: GPL-2.0-only
/*
 * amd_freq_sensitivity.c: AMD frequency sensitivity feedback powersave bias
 *                         for the ondemand governor.
 *
 * Copyright (C) 2013 Advanced Micro Devices, Inc.
 *
 * Author: Jacob Shin <jacob.shin@amd.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/pci.h>
#include <linux/percpu-defs.h>
#include <linux/init.h>

#include <asm/msr.h>
#include <asm/cpufeature.h>
#include <asm/cpu_device_id.h>

#include "cpufreq_ondemand.h"

#define MSR_AMD64_FREQ_SENSITIVITY_ACTUAL       0xc0010080
#define MSR_AMD64_FREQ_SENSITIVITY_REFERENCE    0xc0010081
#define CLASS_CODE_SHIFT                        56
#define POWERSAVE_BIAS_MAX                      1000
#define POWERSAVE_BIAS_DEF                      400

struct cpu_data_t {
        u64 actual;
        u64 reference;
        unsigned int freq_prev;
};

static DEFINE_PER_CPU(struct cpu_data_t, cpu_data);

static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
                                              unsigned int freq_next,
                                              unsigned int relation)
{
        int sensitivity;
        long d_actual, d_reference;
        struct msr actual, reference;
        struct cpu_data_t *data = &per_cpu(cpu_data, policy->cpu);
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct dbs_data *od_data = policy_dbs->dbs_data;
        struct od_dbs_tuners *od_tuners = od_data->tuners;

        if (!policy->freq_table)
                return freq_next;

        rdmsrq_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &actual.q);
        rdmsrq_on_cpu(policy->cpu, MSR_AMD64_FREQ_SENSITIVITY_REFERENCE, &reference.q);
        actual.h &= 0x00ffffff;
        reference.h &= 0x00ffffff;

        /* counter wrapped around, so stay on current frequency */
        if (actual.q < data->actual || reference.q < data->reference) {
                freq_next = policy->cur;
                goto out;
        }

        d_actual = actual.q - data->actual;
        d_reference = reference.q - data->reference;

        /* divide by 0, so stay on current frequency as well */
        if (d_reference == 0) {
                freq_next = policy->cur;
                goto out;
        }

        sensitivity = POWERSAVE_BIAS_MAX -
                (POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);

        clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);

        /* this workload is not CPU bound, so choose a lower freq */
        if (sensitivity < od_tuners->powersave_bias) {
                if (data->freq_prev == policy->cur)
                        freq_next = policy->cur;

                if (freq_next > policy->cur)
                        freq_next = policy->cur;
                else if (freq_next < policy->cur)
                        freq_next = policy->min;
                else {
                        unsigned int index;

                        index = cpufreq_table_find_index_h(policy,
                                                           policy->cur - 1,
                                                           relation & CPUFREQ_RELATION_E);
                        freq_next = policy->freq_table[index].frequency;
                }

                data->freq_prev = freq_next;
        } else
                data->freq_prev = 0;

out:
        data->actual = actual.q;
        data->reference = reference.q;
        return freq_next;
}

static int __init amd_freq_sensitivity_init(void)
{
        u64 val;
        struct pci_dev *pcidev;
        unsigned int pci_vendor;

        if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
                pci_vendor = PCI_VENDOR_ID_AMD;
        else if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
                pci_vendor = PCI_VENDOR_ID_HYGON;
        else
                return -ENODEV;

        pcidev = pci_get_device(pci_vendor,
                        PCI_DEVICE_ID_AMD_KERNCZ_SMBUS, NULL);

        if (!pcidev) {
                if (!boot_cpu_has(X86_FEATURE_PROC_FEEDBACK))
                        return -ENODEV;
        } else {
                pci_dev_put(pcidev);
        }

        if (rdmsrq_safe(MSR_AMD64_FREQ_SENSITIVITY_ACTUAL, &val))
                return -ENODEV;

        if (!(val >> CLASS_CODE_SHIFT))
                return -ENODEV;

        od_register_powersave_bias_handler(amd_powersave_bias_target,
                        POWERSAVE_BIAS_DEF);
        return 0;
}
late_initcall(amd_freq_sensitivity_init);

static void __exit amd_freq_sensitivity_exit(void)
{
        od_unregister_powersave_bias_handler();
}
module_exit(amd_freq_sensitivity_exit);

static const struct x86_cpu_id __maybe_unused amd_freq_sensitivity_ids[] = {
        X86_MATCH_FEATURE(X86_FEATURE_PROC_FEEDBACK, NULL),
        {}
};
MODULE_DEVICE_TABLE(x86cpu, amd_freq_sensitivity_ids);

MODULE_AUTHOR("Jacob Shin <jacob.shin@amd.com>");
MODULE_DESCRIPTION("AMD frequency sensitivity feedback powersave bias for "
                "the ondemand governor.");
MODULE_LICENSE("GPL");