FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/tsc.c

     /*-
      * Copyright (c) 1998-2003 Poul-Henning Kamp
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_clock.h"
    
    #include <sys/param.h>
    #include <sys/bus.h>
    #include <sys/cpu.h>
    #include <sys/malloc.h>
    #include <sys/systm.h>
    #include <sys/sysctl.h>
    #include <sys/time.h>
    #include <sys/timetc.h>
    #include <sys/kernel.h>
    #include <sys/power.h>
    #include <sys/smp.h>
    #include <machine/clock.h>
    #include <machine/md_var.h>
    #include <machine/specialreg.h>
    
    #include "cpufreq_if.h"
    
    uint64_t        tsc_freq;
    int             tsc_is_broken;
    u_int           tsc_present;
    static eventhandler_tag tsc_levels_tag, tsc_pre_tag, tsc_post_tag;
    
    #ifdef SMP
    static int      smp_tsc;
    SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
        "Indicates whether the TSC is safe to use in SMP mode");
    TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
    #endif
    
    static void tsc_freq_changed(void *arg, const struct cf_level *level,
        int status);
    static void tsc_freq_changing(void *arg, const struct cf_level *level,
        int *status);
    static  unsigned tsc_get_timecount(struct timecounter *tc);
    static void tsc_levels_changed(void *arg, int unit);
    
    static struct timecounter tsc_timecounter = {
            tsc_get_timecount,      /* get_timecount */
            0,                      /* no poll_pps */
            ~0u,                    /* counter_mask */
            0,                      /* frequency */
            "TSC",                  /* name */
            800,                    /* quality (adjusted in code) */
    };
    
    void
    init_TSC(void)
    {
            u_int64_t tscval[2];
    
            if (cpu_feature & CPUID_TSC)
                    tsc_present = 1;
            else
                    tsc_present = 0;
    
            if (!tsc_present) 
                    return;
    
            if (bootverbose)
                    printf("Calibrating TSC clock ... ");
    
            tscval[0] = rdtsc();
            DELAY(1000000);
            tscval[1] = rdtsc();
    
            tsc_freq = tscval[1] - tscval[0];
            if (bootverbose)
                    printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq);
   
           /*
            * Inform CPU accounting about our boot-time clock rate.  Once the
            * system is finished booting, we will get the real max clock rate
            * via tsc_freq_max().  This also will be updated if someone loads
            * a cpufreq driver after boot that discovers a new max frequency.
            */
           set_cputicker(rdtsc, tsc_freq, 1);
   
           /* Register to find out about changes in CPU frequency. */
           tsc_pre_tag = EVENTHANDLER_REGISTER(cpufreq_pre_change,
               tsc_freq_changing, NULL, EVENTHANDLER_PRI_FIRST);
           tsc_post_tag = EVENTHANDLER_REGISTER(cpufreq_post_change,
               tsc_freq_changed, NULL, EVENTHANDLER_PRI_FIRST);
           tsc_levels_tag = EVENTHANDLER_REGISTER(cpufreq_levels_changed,
               tsc_levels_changed, NULL, EVENTHANDLER_PRI_ANY);
   }
   
   void
   init_TSC_tc(void)
   {
           /*
            * We can not use the TSC if we support APM.  Precise timekeeping
            * on an APM'ed machine is at best a fools pursuit, since 
            * any and all of the time spent in various SMM code can't 
            * be reliably accounted for.  Reading the RTC is your only
            * source of reliable time info.  The i8254 loses too, of course,
            * but we need to have some kind of time...
            * We don't know at this point whether APM is going to be used
            * or not, nor when it might be activated.  Play it safe.
            */
           if (power_pm_get_type() == POWER_PM_TYPE_APM) {
                   tsc_timecounter.tc_quality = -1000;
                   if (bootverbose)
                           printf("TSC timecounter disabled: APM enabled.\n");
           }
   
   #ifdef SMP
           /*
            * We can not use the TSC in SMP mode unless the TSCs on all CPUs
            * are somehow synchronized.  Some hardware configurations do
            * this, but we have no way of determining whether this is the
            * case, so we do not use the TSC in multi-processor systems
            * unless the user indicated (by setting kern.timecounter.smp_tsc
            * to 1) that he believes that his TSCs are synchronized.
            */
           if (mp_ncpus > 1 && !smp_tsc)
                   tsc_timecounter.tc_quality = -100;
   #endif
   
           if (tsc_present && tsc_freq != 0 && !tsc_is_broken) {
                   tsc_timecounter.tc_frequency = tsc_freq;
                   tc_init(&tsc_timecounter);
           }
   }
   
   /*
    * When cpufreq levels change, find out about the (new) max frequency.  We
    * use this to update CPU accounting in case it got a lower estimate at boot.
    */
   static void
   tsc_levels_changed(void *arg, int unit)
   {
           device_t cf_dev;
           struct cf_level *levels;
           int count, error;
           uint64_t max_freq;
   
           /* Only use values from the first CPU, assuming all are equal. */
           if (unit != 0)
                   return;
   
           /* Find the appropriate cpufreq device instance. */
           cf_dev = devclass_get_device(devclass_find("cpufreq"), unit);
           if (cf_dev == NULL) {
                   printf("tsc_levels_changed() called but no cpufreq device?\n");
                   return;
           }
   
           /* Get settings from the device and find the max frequency. */
           count = 64;
           levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
           if (levels == NULL)
                   return;
           error = CPUFREQ_LEVELS(cf_dev, levels, &count);
           if (error == 0 && count != 0) {
                   max_freq = (uint64_t)levels[0].total_set.freq * 1000000;
                   set_cputicker(rdtsc, max_freq, 1);
           } else
                   printf("tsc_levels_changed: no max freq found\n");
           free(levels, M_TEMP);
   }
   
   /*
    * If the TSC timecounter is in use, veto the pending change.  It may be
    * possible in the future to handle a dynamically-changing timecounter rate.
    */
   static void
   tsc_freq_changing(void *arg, const struct cf_level *level, int *status)
   {
   
           if (*status != 0 || timecounter != &tsc_timecounter)
                   return;
   
           printf("timecounter TSC must not be in use when "
                "changing frequencies; change denied\n");
           *status = EBUSY;
   }
   
   /* Update TSC freq with the value indicated by the caller. */
   static void
   tsc_freq_changed(void *arg, const struct cf_level *level, int status)
   {
           /* If there was an error during the transition, don't do anything. */
           if (status != 0)
                   return;
   
           /* Total setting for this level gives the new frequency in MHz. */
           tsc_freq = (uint64_t)level->total_set.freq * 1000000;
           tsc_timecounter.tc_frequency = tsc_freq;
   }
   
   static int
   sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
   {
           int error;
           uint64_t freq;
   
           if (tsc_timecounter.tc_frequency == 0)
                   return (EOPNOTSUPP);
           freq = tsc_freq;
           error = sysctl_handle_quad(oidp, &freq, 0, req);
           if (error == 0 && req->newptr != NULL) {
                   tsc_freq = freq;
                   tsc_timecounter.tc_frequency = tsc_freq;
           }
           return (error);
   }
   
   SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_QUAD | CTLFLAG_RW,
       0, sizeof(u_int), sysctl_machdep_tsc_freq, "QU", "");
   
   static unsigned
   tsc_get_timecount(struct timecounter *tc)
   {
           return (rdtsc());
   }

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