The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/tsc.c

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    1 /*-
    2  * Copyright (c) 1998-2003 Poul-Henning Kamp
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD$");
   29 
   30 #include "opt_clock.h"
   31 
   32 #include <sys/param.h>
   33 #include <sys/bus.h>
   34 #include <sys/cpu.h>
   35 #include <sys/malloc.h>
   36 #include <sys/systm.h>
   37 #include <sys/sysctl.h>
   38 #include <sys/time.h>
   39 #include <sys/timetc.h>
   40 #include <sys/kernel.h>
   41 #include <sys/power.h>
   42 #include <sys/smp.h>
   43 #include <machine/clock.h>
   44 #include <machine/md_var.h>
   45 #include <machine/specialreg.h>
   46 
   47 #include "cpufreq_if.h"
   48 
   49 uint64_t        tsc_freq;
   50 int             tsc_is_broken;
   51 static eventhandler_tag tsc_levels_tag, tsc_pre_tag, tsc_post_tag;
   52 
   53 #ifdef SMP
   54 static int      smp_tsc;
   55 SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
   56     "Indicates whether the TSC is safe to use in SMP mode");
   57 TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
   58 #endif
   59 
   60 static void tsc_freq_changed(void *arg, const struct cf_level *level,
   61     int status);
   62 static void tsc_freq_changing(void *arg, const struct cf_level *level,
   63     int *status);
   64 static  unsigned tsc_get_timecount(struct timecounter *tc);
   65 static void tsc_levels_changed(void *arg, int unit);
   66 
   67 static struct timecounter tsc_timecounter = {
   68         tsc_get_timecount,      /* get_timecount */
   69         0,                      /* no poll_pps */
   70         ~0u,                    /* counter_mask */
   71         0,                      /* frequency */
   72         "TSC",                  /* name */
   73         800,                    /* quality (adjusted in code) */
   74 };
   75 
   76 void
   77 init_TSC(void)
   78 {
   79         u_int64_t tscval[2];
   80 
   81         if (bootverbose)
   82                 printf("Calibrating TSC clock ... ");
   83 
   84         tscval[0] = rdtsc();
   85         DELAY(1000000);
   86         tscval[1] = rdtsc();
   87 
   88         tsc_freq = tscval[1] - tscval[0];
   89         if (bootverbose)
   90                 printf("TSC clock: %lu Hz\n", tsc_freq);
   91 
   92         /*
   93          * Inform CPU accounting about our boot-time clock rate.  Once the
   94          * system is finished booting, we will get the real max clock rate
   95          * via tsc_freq_max().  This also will be updated if someone loads
   96          * a cpufreq driver after boot that discovers a new max frequency.
   97          */
   98         set_cputicker(rdtsc, tsc_freq, 1);
   99 
  100         /* Register to find out about changes in CPU frequency. */
  101         tsc_pre_tag = EVENTHANDLER_REGISTER(cpufreq_pre_change,
  102             tsc_freq_changing, NULL, EVENTHANDLER_PRI_FIRST);
  103         tsc_post_tag = EVENTHANDLER_REGISTER(cpufreq_post_change,
  104             tsc_freq_changed, NULL, EVENTHANDLER_PRI_FIRST);
  105         tsc_levels_tag = EVENTHANDLER_REGISTER(cpufreq_levels_changed,
  106             tsc_levels_changed, NULL, EVENTHANDLER_PRI_ANY);
  107 }
  108 
  109 void
  110 init_TSC_tc(void)
  111 {
  112 
  113 #ifdef SMP
  114         /*
  115          * We can not use the TSC in SMP mode unless the TSCs on all CPUs
  116          * are somehow synchronized.  Some hardware configurations do
  117          * this, but we have no way of determining whether this is the
  118          * case, so we do not use the TSC in multi-processor systems
  119          * unless the user indicated (by setting kern.timecounter.smp_tsc
  120          * to 1) that he believes that his TSCs are synchronized.
  121          */
  122         if (mp_ncpus > 1 && !smp_tsc)
  123                 tsc_timecounter.tc_quality = -100;
  124 #endif
  125 
  126         if (tsc_freq != 0 && !tsc_is_broken) {
  127                 tsc_timecounter.tc_frequency = tsc_freq;
  128                 tc_init(&tsc_timecounter);
  129         }
  130 }
  131 
  132 /*
  133  * When cpufreq levels change, find out about the (new) max frequency.  We
  134  * use this to update CPU accounting in case it got a lower estimate at boot.
  135  */
  136 static void
  137 tsc_levels_changed(void *arg, int unit)
  138 {
  139         device_t cf_dev;
  140         struct cf_level *levels;
  141         int count, error;
  142         uint64_t max_freq;
  143 
  144         /* Only use values from the first CPU, assuming all are equal. */
  145         if (unit != 0)
  146                 return;
  147 
  148         /* Find the appropriate cpufreq device instance. */
  149         cf_dev = devclass_get_device(devclass_find("cpufreq"), unit);
  150         if (cf_dev == NULL) {
  151                 printf("tsc_levels_changed() called but no cpufreq device?\n");
  152                 return;
  153         }
  154 
  155         /* Get settings from the device and find the max frequency. */
  156         count = 64;
  157         levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
  158         if (levels == NULL)
  159                 return;
  160         error = CPUFREQ_LEVELS(cf_dev, levels, &count);
  161         if (error == 0 && count != 0) {
  162                 max_freq = (uint64_t)levels[0].total_set.freq * 1000000;
  163                 set_cputicker(rdtsc, max_freq, 1);
  164         } else
  165                 printf("tsc_levels_changed: no max freq found\n");
  166         free(levels, M_TEMP);
  167 }
  168 
  169 /*
  170  * If the TSC timecounter is in use, veto the pending change.  It may be
  171  * possible in the future to handle a dynamically-changing timecounter rate.
  172  */
  173 static void
  174 tsc_freq_changing(void *arg, const struct cf_level *level, int *status)
  175 {
  176 
  177         if (*status != 0 || timecounter != &tsc_timecounter)
  178                 return;
  179 
  180         printf("timecounter TSC must not be in use when "
  181              "changing frequencies; change denied\n");
  182         *status = EBUSY;
  183 }
  184 
  185 /* Update TSC freq with the value indicated by the caller. */
  186 static void
  187 tsc_freq_changed(void *arg, const struct cf_level *level, int status)
  188 {
  189         /* If there was an error during the transition, don't do anything. */
  190         if (status != 0)
  191                 return;
  192 
  193         /* Total setting for this level gives the new frequency in MHz. */
  194         tsc_freq = (uint64_t)level->total_set.freq * 1000000;
  195         tsc_timecounter.tc_frequency = tsc_freq;
  196 }
  197 
  198 static int
  199 sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
  200 {
  201         int error;
  202         uint64_t freq;
  203 
  204         if (tsc_timecounter.tc_frequency == 0)
  205                 return (EOPNOTSUPP);
  206         freq = tsc_freq;
  207         error = sysctl_handle_quad(oidp, &freq, 0, req);
  208         if (error == 0 && req->newptr != NULL) {
  209                 tsc_freq = freq;
  210                 tsc_timecounter.tc_frequency = tsc_freq;
  211         }
  212         return (error);
  213 }
  214 
  215 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_QUAD | CTLFLAG_RW,
  216     0, sizeof(u_int), sysctl_machdep_tsc_freq, "QU", "");
  217 
  218 static unsigned
  219 tsc_get_timecount(struct timecounter *tc)
  220 {
  221         return (rdtsc());
  222 }

Cache object: 2d2462eb5d58e7007ea0fe4438e95e9b


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