// SPDX-License-Identifier: GPL-2.0-only
/*
 *  (C) 2010,2011       Thomas Renninger <trenn@suse.de>, Novell Inc.
 */

#if defined(__i386__) || defined(__x86_64__)

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#include <cpufreq.h>

#include "helpers/helpers.h"
#include "idle_monitor/cpupower-monitor.h"

#define MSR_APERF       0xE8
#define MSR_MPERF       0xE7

#define MSR_TSC 0x10

#define MSR_AMD_HWCR 0xc0010015

enum mperf_id { C0 = 0, Cx, AVG_FREQ, MPERF_CSTATE_COUNT };

static int mperf_get_count_percent(unsigned int self_id, double *percent,
                                   unsigned int cpu);
static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
                                unsigned int cpu);
static struct timespec time_start, time_end;

static cstate_t mperf_cstates[MPERF_CSTATE_COUNT] = {
        {
                .name                   = "C0",
                .desc                   = N_("Processor Core not idle"),
                .id                     = C0,
                .range                  = RANGE_THREAD,
                .get_count_percent      = mperf_get_count_percent,
        },
        {
                .name                   = "Cx",
                .desc                   = N_("Processor Core in an idle state"),
                .id                     = Cx,
                .range                  = RANGE_THREAD,
                .get_count_percent      = mperf_get_count_percent,
        },

        {
                .name                   = "Freq",
                .desc                   = N_("Average Frequency (including boost) in MHz"),
                .id                     = AVG_FREQ,
                .range                  = RANGE_THREAD,
                .get_count              = mperf_get_count_freq,
        },
};

enum MAX_FREQ_MODE { MAX_FREQ_SYSFS, MAX_FREQ_TSC_REF };
static int max_freq_mode;
/*
 * The max frequency mperf is ticking at (in C0), either retrieved via:
 *   1) calculated after measurements if we know TSC ticks at mperf/P0 frequency
 *   2) cpufreq /sys/devices/.../cpu0/cpufreq/cpuinfo_max_freq at init time
 * 1. Is preferred as it also works without cpufreq subsystem (e.g. on Xen)
 */
static unsigned long max_frequency;

static unsigned long long tsc_at_measure_start;
static unsigned long long tsc_at_measure_end;
static unsigned long long *mperf_previous_count;
static unsigned long long *aperf_previous_count;
static unsigned long long *mperf_current_count;
static unsigned long long *aperf_current_count;

/* valid flag for all CPUs. If a MSR read failed it will be zero */
static int *is_valid;

static int mperf_get_tsc(unsigned long long *tsc)
{
        int ret;

        ret = read_msr(base_cpu, MSR_TSC, tsc);
        if (ret)
                dprint("Reading TSC MSR failed, returning %llu\n", *tsc);
        return ret;
}

static int mperf_init_stats(unsigned int cpu)
{
        unsigned long long val;
        int ret;

        ret = read_msr(cpu, MSR_APERF, &val);
        aperf_previous_count[cpu] = val;
        ret |= read_msr(cpu, MSR_MPERF, &val);
        mperf_previous_count[cpu] = val;
        is_valid[cpu] = !ret;

        return 0;
}

static int mperf_measure_stats(unsigned int cpu)
{
        unsigned long long val;
        int ret;

        ret = read_msr(cpu, MSR_APERF, &val);
        aperf_current_count[cpu] = val;
        ret |= read_msr(cpu, MSR_MPERF, &val);
        mperf_current_count[cpu] = val;
        is_valid[cpu] = !ret;

        return 0;
}

static int mperf_get_count_percent(unsigned int id, double *percent,
                                   unsigned int cpu)
{
        unsigned long long aperf_diff, mperf_diff, tsc_diff;
        unsigned long long timediff;

        if (!is_valid[cpu])
                return -1;

        if (id != C0 && id != Cx)
                return -1;

        mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
        aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];

        if (max_freq_mode == MAX_FREQ_TSC_REF) {
                tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
                *percent = 100.0 * mperf_diff / tsc_diff;
                dprint("%s: TSC Ref - mperf_diff: %llu, tsc_diff: %llu\n",
                       mperf_cstates[id].name, mperf_diff, tsc_diff);
        } else if (max_freq_mode == MAX_FREQ_SYSFS) {
                timediff = max_frequency * timespec_diff_us(time_start, time_end);
                *percent = 100.0 * mperf_diff / timediff;
                dprint("%s: MAXFREQ - mperf_diff: %llu, time_diff: %llu\n",
                       mperf_cstates[id].name, mperf_diff, timediff);
        } else
                return -1;

        if (id == Cx)
                *percent = 100.0 - *percent;

        dprint("%s: previous: %llu - current: %llu - (%u)\n",
                mperf_cstates[id].name, mperf_diff, aperf_diff, cpu);
        dprint("%s: %f\n", mperf_cstates[id].name, *percent);
        return 0;
}

static int mperf_get_count_freq(unsigned int id, unsigned long long *count,
                                unsigned int cpu)
{
        unsigned long long aperf_diff, mperf_diff, time_diff, tsc_diff;

        if (id != AVG_FREQ)
                return 1;

        if (!is_valid[cpu])
                return -1;

        mperf_diff = mperf_current_count[cpu] - mperf_previous_count[cpu];
        aperf_diff = aperf_current_count[cpu] - aperf_previous_count[cpu];

        if (max_freq_mode == MAX_FREQ_TSC_REF) {
                /* Calculate max_freq from TSC count */
                tsc_diff = tsc_at_measure_end - tsc_at_measure_start;
                time_diff = timespec_diff_us(time_start, time_end);
                max_frequency = tsc_diff / time_diff;
        }

        *count = max_frequency * ((double)aperf_diff / mperf_diff);
        dprint("%s: Average freq based on %s maximum frequency:\n",
               mperf_cstates[id].name,
               (max_freq_mode == MAX_FREQ_TSC_REF) ? "TSC calculated" : "sysfs read");
        dprint("max_frequency: %lu\n", max_frequency);
        dprint("aperf_diff: %llu\n", aperf_diff);
        dprint("mperf_diff: %llu\n", mperf_diff);
        dprint("avg freq:   %llu\n", *count);
        return 0;
}

static int mperf_start(void)
{
        int cpu;
        unsigned long long dbg;

        clock_gettime(CLOCK_REALTIME, &time_start);
        mperf_get_tsc(&tsc_at_measure_start);

        for (cpu = 0; cpu < cpu_count; cpu++)
                mperf_init_stats(cpu);

        mperf_get_tsc(&dbg);
        dprint("TSC diff: %llu\n", dbg - tsc_at_measure_start);
        return 0;
}

static int mperf_stop(void)
{
        unsigned long long dbg;
        int cpu;

        for (cpu = 0; cpu < cpu_count; cpu++)
                mperf_measure_stats(cpu);

        mperf_get_tsc(&tsc_at_measure_end);
        clock_gettime(CLOCK_REALTIME, &time_end);

        mperf_get_tsc(&dbg);
        dprint("TSC diff: %llu\n", dbg - tsc_at_measure_end);

        return 0;
}

/*
 * Mperf register is defined to tick at P0 (maximum) frequency
 *
 * Instead of reading out P0 which can be tricky to read out from HW,
 * we use TSC counter if it reliably ticks at P0/mperf frequency.
 *
 * Still try to fall back to:
 * /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
 * on older Intel HW without invariant TSC feature.
 * Or on AMD machines where TSC does not tick at P0 (do not exist yet, but
 * it's still double checked (MSR_AMD_HWCR)).
 *
 * On these machines the user would still get useful mperf
 * stats when acpi-cpufreq driver is loaded.
 */
static int init_maxfreq_mode(void)
{
        int ret;
        unsigned long long hwcr;
        unsigned long min;

        if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_INV_TSC))
                goto use_sysfs;

        if (cpupower_cpu_info.vendor == X86_VENDOR_AMD ||
            cpupower_cpu_info.vendor == X86_VENDOR_HYGON) {
                /* MSR_AMD_HWCR tells us whether TSC runs at P0/mperf
                 * freq.
                 * A test whether hwcr is accessable/available would be:
                 * (cpupower_cpu_info.family > 0x10 ||
                 *   cpupower_cpu_info.family == 0x10 &&
                 *   cpupower_cpu_info.model >= 0x2))
                 * This should be the case for all aperf/mperf
                 * capable AMD machines and is therefore safe to test here.
                 * Compare with Linus kernel git commit: acf01734b1747b1ec4
                 */
                ret = read_msr(0, MSR_AMD_HWCR, &hwcr);
                /*
                 * If the MSR read failed, assume a Xen system that did
                 * not explicitly provide access to it and assume TSC works
                */
                if (ret != 0) {
                        dprint("TSC read 0x%x failed - assume TSC working\n",
                               MSR_AMD_HWCR);
                        return 0;
                } else if (1 & (hwcr >> 24)) {
                        max_freq_mode = MAX_FREQ_TSC_REF;
                        return 0;
                } else { /* Use sysfs max frequency if available */ }
        } else if (cpupower_cpu_info.vendor == X86_VENDOR_INTEL) {
                /*
                 * On Intel we assume mperf (in C0) is ticking at same
                 * rate than TSC
                 */
                max_freq_mode = MAX_FREQ_TSC_REF;
                return 0;
        }
use_sysfs:
        if (cpufreq_get_hardware_limits(0, &min, &max_frequency)) {
                dprint("Cannot retrieve max freq from cpufreq kernel "
                       "subsystem\n");
                return -1;
        }
        max_freq_mode = MAX_FREQ_SYSFS;
        max_frequency /= 1000; /* Default automatically to MHz value */
        return 0;
}

/*
 * This monitor provides:
 *
 * 1) Average frequency a CPU resided in
 *    This always works if the CPU has aperf/mperf capabilities
 *
 * 2) C0 and Cx (any sleep state) time a CPU resided in
 *    Works if mperf timer stops ticking in sleep states which
 *    seem to be the case on all current HW.
 * Both is directly retrieved from HW registers and is independent
 * from kernel statistics.
 */
struct cpuidle_monitor mperf_monitor;
struct cpuidle_monitor *mperf_register(void)
{
        if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_APERF))
                return NULL;

        if (init_maxfreq_mode())
                return NULL;

        /* Free this at program termination */
        is_valid = calloc(cpu_count, sizeof(int));
        mperf_previous_count = calloc(cpu_count, sizeof(unsigned long long));
        aperf_previous_count = calloc(cpu_count, sizeof(unsigned long long));
        mperf_current_count = calloc(cpu_count, sizeof(unsigned long long));
        aperf_current_count = calloc(cpu_count, sizeof(unsigned long long));

        mperf_monitor.name_len = strlen(mperf_monitor.name);
        return &mperf_monitor;
}

void mperf_unregister(void)
{
        free(mperf_previous_count);
        free(aperf_previous_count);
        free(mperf_current_count);
        free(aperf_current_count);
        free(is_valid);
}

struct cpuidle_monitor mperf_monitor = {
        .name                   = "Mperf",
        .hw_states_num          = MPERF_CSTATE_COUNT,
        .hw_states              = mperf_cstates,
        .start                  = mperf_start,
        .stop                   = mperf_stop,
        .do_register            = mperf_register,
        .unregister             = mperf_unregister,
        .needs_root             = 1,
        .overflow_s             = 922000000 /* 922337203 seconds TSC overflow
                                               at 20GHz */
};
#endif /* #if defined(__i386__) || defined(__x86_64__) */