// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>

#include "../../../util/debug.h"
#include "../../../util/tsc.h"
#include "cpuid.h"

u64 rdtsc(void)
{
        unsigned int low, high;

        asm volatile("rdtsc" : "=a" (low), "=d" (high));

        return low | ((u64)high) << 32;
}

/*
 * Derive the TSC frequency in Hz from the /proc/cpuinfo, for example:
 * ...
 * model name      : Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz
 * ...
 * will return 3000000000.
 */
static u64 cpuinfo_tsc_freq(void)
{
        u64 result = 0;
        FILE *cpuinfo;
        char *line = NULL;
        size_t len = 0;

        cpuinfo = fopen("/proc/cpuinfo", "r");
        if (!cpuinfo) {
                pr_err("Failed to read /proc/cpuinfo for TSC frequency\n");
                return 0;
        }
        while (getline(&line, &len, cpuinfo) > 0) {
                if (!strncmp(line, "model name", 10)) {
                        char *pos = strstr(line + 11, " @ ");
                        double float_result;

                        if (pos && sscanf(pos, " @ %lfGHz", &float_result) == 1) {
                                float_result *= 1000000000;
                                result = (u64)float_result;
                                goto out;
                        }
                }
        }
out:
        if (result == 0)
                pr_err("Failed to find TSC frequency in /proc/cpuinfo\n");

        free(line);
        fclose(cpuinfo);
        return result;
}

u64 arch_get_tsc_freq(void)
{
        unsigned int a, b, c, d, lvl;
        static bool cached;
        static double tsc;
        char vendor[16];

        if (cached)
                return tsc;

        cached = true;
        get_cpuid_0(vendor, &lvl);
        if (!strstr(vendor, "Intel"))
                return 0;

        /*
         * Don't support Time Stamp Counter and
         * Nominal Core Crystal Clock Information Leaf.
         */
        if (lvl < 0x15) {
                tsc = cpuinfo_tsc_freq();
                return tsc;
        }

        cpuid(0x15, 0, &a, &b, &c, &d);
        /* TSC frequency is not enumerated */
        if (!a || !b || !c) {
                tsc = cpuinfo_tsc_freq();
                return tsc;
        }

        tsc = (u64)c * (u64)b / (u64)a;
        return tsc;
}