/*
 * x86_energy_perf_policy -- set the energy versus performance
 * policy preference bias on recent X86 processors.
 */
/*
 * Copyright (c) 2010, Intel Corporation.
 * Len Brown <len.brown@intel.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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 St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/time.h>
#include <stdlib.h>
#include <string.h>

unsigned int verbose;           /* set with -v */
unsigned int read_only;         /* set with -r */
char *progname;
unsigned long long new_bias;
int cpu = -1;

/*
 * Usage:
 *
 * -c cpu: limit action to a single CPU (default is all CPUs)
 * -v: verbose output (can invoke more than once)
 * -r: read-only, don't change any settings
 *
 *  performance
 *      Performance is paramount.
 *      Unwilling to sacrifice any performance
 *      for the sake of energy saving. (hardware default)
 *
 *  normal
 *      Can tolerate minor performance compromise
 *      for potentially significant energy savings.
 *      (reasonable default for most desktops and servers)
 *
 *  powersave
 *      Can tolerate significant performance hit
 *      to maximize energy savings.
 *
 * n
 *      a numerical value to write to the underlying MSR.
 */
void usage(void)
{
        printf("%s: [-c cpu] [-v] "
                "(-r | 'performance' | 'normal' | 'powersave' | n)\n",
                progname);
        exit(1);
}

#define MSR_IA32_ENERGY_PERF_BIAS       0x000001b0

#define BIAS_PERFORMANCE                0
#define BIAS_BALANCE                    6
#define BIAS_POWERSAVE                  15

void cmdline(int argc, char **argv)
{
        int opt;

        progname = argv[0];

        while ((opt = getopt(argc, argv, "+rvc:")) != -1) {
                switch (opt) {
                case 'c':
                        cpu = atoi(optarg);
                        break;
                case 'r':
                        read_only = 1;
                        break;
                case 'v':
                        verbose++;
                        break;
                default:
                        usage();
                }
        }
        /* if -r, then should be no additional optind */
        if (read_only && (argc > optind))
                usage();

        /*
         * if no -r , then must be one additional optind
         */
        if (!read_only) {

                if (argc != optind + 1) {
                        printf("must supply -r or policy param\n");
                        usage();
                        }

                if (!strcmp("performance", argv[optind])) {
                        new_bias = BIAS_PERFORMANCE;
                } else if (!strcmp("normal", argv[optind])) {
                        new_bias = BIAS_BALANCE;
                } else if (!strcmp("powersave", argv[optind])) {
                        new_bias = BIAS_POWERSAVE;
                } else {
                        char *endptr;

                        new_bias = strtoull(argv[optind], &endptr, 0);
                        if (endptr == argv[optind] ||
                                new_bias > BIAS_POWERSAVE) {
                                        fprintf(stderr, "invalid value: %s\n",
                                                argv[optind]);
                                usage();
                        }
                }
        }
}

/*
 * validate_cpuid()
 * returns on success, quietly exits on failure (make verbose with -v)
 */
void validate_cpuid(void)
{
        unsigned int eax, ebx, ecx, edx, max_level;
        unsigned int fms, family, model, stepping;

        eax = ebx = ecx = edx = 0;

        asm("cpuid" : "=a" (max_level), "=b" (ebx), "=c" (ecx),
                "=d" (edx) : "a" (0));

        if (ebx != 0x756e6547 || edx != 0x49656e69 || ecx != 0x6c65746e) {
                if (verbose)
                        fprintf(stderr, "%.4s%.4s%.4s != GenuineIntel",
                                (char *)&ebx, (char *)&edx, (char *)&ecx);
                exit(1);
        }

        asm("cpuid" : "=a" (fms), "=c" (ecx), "=d" (edx) : "a" (1) : "ebx");
        family = (fms >> 8) & 0xf;
        model = (fms >> 4) & 0xf;
        stepping = fms & 0xf;
        if (family == 6 || family == 0xf)
                model += ((fms >> 16) & 0xf) << 4;

        if (verbose > 1)
                printf("CPUID %d levels family:model:stepping "
                        "0x%x:%x:%x (%d:%d:%d)\n", max_level,
                        family, model, stepping, family, model, stepping);

        if (!(edx & (1 << 5))) {
                if (verbose)
                        printf("CPUID: no MSR\n");
                exit(1);
        }

        /*
         * Support for MSR_IA32_ENERGY_PERF_BIAS
         * is indicated by CPUID.06H.ECX.bit3
         */
        asm("cpuid" : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) : "a" (6));
        if (verbose)
                printf("CPUID.06H.ECX: 0x%x\n", ecx);
        if (!(ecx & (1 << 3))) {
                if (verbose)
                        printf("CPUID: No MSR_IA32_ENERGY_PERF_BIAS\n");
                exit(1);
        }
        return; /* success */
}

unsigned long long get_msr(int cpu, int offset)
{
        unsigned long long msr;
        char msr_path[32];
        int retval;
        int fd;

        sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
        fd = open(msr_path, O_RDONLY);
        if (fd < 0) {
                printf("Try \"# modprobe msr\"\n");
                perror(msr_path);
                exit(1);
        }

        retval = pread(fd, &msr, sizeof msr, offset);

        if (retval != sizeof msr) {
                printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
                exit(-2);
        }
        close(fd);
        return msr;
}

unsigned long long  put_msr(int cpu, unsigned long long new_msr, int offset)
{
        unsigned long long old_msr;
        char msr_path[32];
        int retval;
        int fd;

        sprintf(msr_path, "/dev/cpu/%d/msr", cpu);
        fd = open(msr_path, O_RDWR);
        if (fd < 0) {
                perror(msr_path);
                exit(1);
        }

        retval = pread(fd, &old_msr, sizeof old_msr, offset);
        if (retval != sizeof old_msr) {
                perror("pwrite");
                printf("pread cpu%d 0x%x = %d\n", cpu, offset, retval);
                exit(-2);
        }

        retval = pwrite(fd, &new_msr, sizeof new_msr, offset);
        if (retval != sizeof new_msr) {
                perror("pwrite");
                printf("pwrite cpu%d 0x%x = %d\n", cpu, offset, retval);
                exit(-2);
        }

        close(fd);

        return old_msr;
}

void print_msr(int cpu)
{
        printf("cpu%d: 0x%016llx\n",
                cpu, get_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS));
}

void update_msr(int cpu)
{
        unsigned long long previous_msr;

        previous_msr = put_msr(cpu, new_bias, MSR_IA32_ENERGY_PERF_BIAS);

        if (verbose)
                printf("cpu%d  msr0x%x 0x%016llx -> 0x%016llx\n",
                        cpu, MSR_IA32_ENERGY_PERF_BIAS, previous_msr, new_bias);

        return;
}

char *proc_stat = "/proc/stat";
/*
 * run func() on every cpu in /dev/cpu
 */
void for_every_cpu(void (func)(int))
{
        FILE *fp;
        int retval;

        fp = fopen(proc_stat, "r");
        if (fp == NULL) {
                perror(proc_stat);
                exit(1);
        }

        retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
        if (retval != 0) {
                perror("/proc/stat format");
                exit(1);
        }

        while (1) {
                int cpu;

                retval = fscanf(fp,
                        "cpu%u %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n",
                        &cpu);
                if (retval != 1)
                        break;

                func(cpu);
        }
        fclose(fp);
}

int main(int argc, char **argv)
{
        cmdline(argc, argv);

        if (verbose > 1)
                printf("x86_energy_perf_policy Nov 24, 2010"
                                " - Len Brown <lenb@kernel.org>\n");
        if (verbose > 1 && !read_only)
                printf("new_bias %lld\n", new_bias);

        validate_cpuid();

        if (cpu != -1) {
                if (read_only)
                        print_msr(cpu);
                else
                        update_msr(cpu);
        } else {
                if (read_only)
                        for_every_cpu(print_msr);
                else
                        for_every_cpu(update_msr);
        }

        return 0;
}