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 #include "opt_kdtrace.h"
   32 
   33 #include <sys/param.h>
   34 #include <sys/bus.h>
   35 #include <sys/cpu.h>
   36 #include <sys/malloc.h>
   37 #include <sys/systm.h>
   38 #include <sys/sysctl.h>
   39 #include <sys/time.h>
   40 #include <sys/timetc.h>
   41 #include <sys/kernel.h>
   42 #include <sys/power.h>
   43 #include <sys/smp.h>
   44 #include <machine/clock.h>
   45 #include <machine/md_var.h>
   46 #include <machine/specialreg.h>
   47 
   48 #ifdef KDTRACE_HOOKS
   49 #include <sys/dtrace_bsd.h>
   50 #endif
   51 
   52 #include "cpufreq_if.h"
   53 
   54 uint64_t        tsc_freq;
   55 int             tsc_is_broken;
   56 int             tsc_is_invariant;
   57 static eventhandler_tag tsc_levels_tag, tsc_pre_tag, tsc_post_tag;
   58 
   59 SYSCTL_INT(_kern_timecounter, OID_AUTO, invariant_tsc, CTLFLAG_RDTUN,
   60     &tsc_is_invariant, 0, "Indicates whether the TSC is P-state invariant");
   61 TUNABLE_INT("kern.timecounter.invariant_tsc", &tsc_is_invariant);
   62 
   63 #ifdef SMP
   64 static int      smp_tsc;
   65 SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
   66     "Indicates whether the TSC is safe to use in SMP mode");
   67 TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
   68 #endif
   69 
   70 static void tsc_freq_changed(void *arg, const struct cf_level *level,
   71     int status);
   72 static void tsc_freq_changing(void *arg, const struct cf_level *level,
   73     int *status);
   74 static  unsigned tsc_get_timecount(struct timecounter *tc);
   75 static void tsc_levels_changed(void *arg, int unit);
   76 
   77 static struct timecounter tsc_timecounter = {
   78         tsc_get_timecount,      /* get_timecount */
   79         0,                      /* no poll_pps */
   80         ~0u,                    /* counter_mask */
   81         0,                      /* frequency */
   82         "TSC",                  /* name */
   83         800,                    /* quality (adjusted in code) */
   84 };
   85 
   86 void
   87 init_TSC(void)
   88 {
   89         u_int64_t tscval[2];
   90 
   91         if (bootverbose)
   92                 printf("Calibrating TSC clock ... ");
   93 
   94         tscval[0] = rdtsc();
   95         DELAY(1000000);
   96         tscval[1] = rdtsc();
   97 
   98         tsc_freq = tscval[1] - tscval[0];
   99         if (bootverbose)
  100                 printf("TSC clock: %lu Hz\n", tsc_freq);
  101 
  102         /*
  103          * Inform CPU accounting about our boot-time clock rate.  Once the
  104          * system is finished booting, we will get the real max clock rate
  105          * via tsc_freq_max().  This also will be updated if someone loads
  106          * a cpufreq driver after boot that discovers a new max frequency.
  107          */
  108         set_cputicker(rdtsc, tsc_freq, 1);
  109 
  110         /* Register to find out about changes in CPU frequency. */
  111         tsc_pre_tag = EVENTHANDLER_REGISTER(cpufreq_pre_change,
  112             tsc_freq_changing, NULL, EVENTHANDLER_PRI_FIRST);
  113         tsc_post_tag = EVENTHANDLER_REGISTER(cpufreq_post_change,
  114             tsc_freq_changed, NULL, EVENTHANDLER_PRI_FIRST);
  115         tsc_levels_tag = EVENTHANDLER_REGISTER(cpufreq_levels_changed,
  116             tsc_levels_changed, NULL, EVENTHANDLER_PRI_ANY);
  117 }
  118 
  119 void
  120 init_TSC_tc(void)
  121 {
  122 
  123 #ifdef SMP
  124         /*
  125          * We can not use the TSC in SMP mode unless the TSCs on all CPUs
  126          * are somehow synchronized.  Some hardware configurations do
  127          * this, but we have no way of determining whether this is the
  128          * case, so we do not use the TSC in multi-processor systems
  129          * unless the user indicated (by setting kern.timecounter.smp_tsc
  130          * to 1) that he believes that his TSCs are synchronized.
  131          */
  132         if (mp_ncpus > 1 && !smp_tsc)
  133                 tsc_timecounter.tc_quality = -100;
  134 #endif
  135 
  136         if (tsc_freq != 0 && !tsc_is_broken) {
  137                 tsc_timecounter.tc_frequency = tsc_freq;
  138                 tc_init(&tsc_timecounter);
  139         }
  140 }
  141 
  142 /*
  143  * When cpufreq levels change, find out about the (new) max frequency.  We
  144  * use this to update CPU accounting in case it got a lower estimate at boot.
  145  */
  146 static void
  147 tsc_levels_changed(void *arg, int unit)
  148 {
  149         device_t cf_dev;
  150         struct cf_level *levels;
  151         int count, error;
  152         uint64_t max_freq;
  153 
  154         /* Only use values from the first CPU, assuming all are equal. */
  155         if (unit != 0)
  156                 return;
  157 
  158         /* Find the appropriate cpufreq device instance. */
  159         cf_dev = devclass_get_device(devclass_find("cpufreq"), unit);
  160         if (cf_dev == NULL) {
  161                 printf("tsc_levels_changed() called but no cpufreq device?\n");
  162                 return;
  163         }
  164 
  165         /* Get settings from the device and find the max frequency. */
  166         count = 64;
  167         levels = malloc(count * sizeof(*levels), M_TEMP, M_NOWAIT);
  168         if (levels == NULL)
  169                 return;
  170         error = CPUFREQ_LEVELS(cf_dev, levels, &count);
  171         if (error == 0 && count != 0) {
  172                 max_freq = (uint64_t)levels[0].total_set.freq * 1000000;
  173                 set_cputicker(rdtsc, max_freq, 1);
  174         } else
  175                 printf("tsc_levels_changed: no max freq found\n");
  176         free(levels, M_TEMP);
  177 }
  178 
  179 /*
  180  * If the TSC timecounter is in use, veto the pending change.  It may be
  181  * possible in the future to handle a dynamically-changing timecounter rate.
  182  */
  183 static void
  184 tsc_freq_changing(void *arg, const struct cf_level *level, int *status)
  185 {
  186 
  187         if (*status != 0 || timecounter != &tsc_timecounter ||
  188             tsc_is_invariant)
  189                 return;
  190 
  191         printf("timecounter TSC must not be in use when "
  192             "changing frequencies; change denied\n");
  193         *status = EBUSY;
  194 }
  195 
  196 /* Update TSC freq with the value indicated by the caller. */
  197 static void
  198 tsc_freq_changed(void *arg, const struct cf_level *level, int status)
  199 {
  200         /*
  201          * If there was an error during the transition or
  202          * TSC is P-state invariant, don't do anything.
  203          */
  204         if (status != 0 || tsc_is_invariant)
  205                 return;
  206 
  207         /* Total setting for this level gives the new frequency in MHz. */
  208         tsc_freq = (uint64_t)level->total_set.freq * 1000000;
  209         tsc_timecounter.tc_frequency = tsc_freq;
  210 }
  211 
  212 static int
  213 sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
  214 {
  215         int error;
  216         uint64_t freq;
  217 
  218         if (tsc_timecounter.tc_frequency == 0)
  219                 return (EOPNOTSUPP);
  220         freq = tsc_freq;
  221         error = sysctl_handle_quad(oidp, &freq, 0, req);
  222         if (error == 0 && req->newptr != NULL) {
  223                 tsc_freq = freq;
  224                 tsc_timecounter.tc_frequency = tsc_freq;
  225         }
  226         return (error);
  227 }
  228 
  229 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_QUAD | CTLFLAG_RW,
  230     0, sizeof(u_int), sysctl_machdep_tsc_freq, "QU", "");
  231 
  232 static unsigned
  233 tsc_get_timecount(struct timecounter *tc)
  234 {
  235         return (rdtsc());
  236 }
  237 
  238 #ifdef KDTRACE_HOOKS
  239 /*
  240  * DTrace needs a high resolution time function which can
  241  * be called from a probe context and guaranteed not to have
  242  * instrumented with probes itself.
  243  *
  244  * Returns nanoseconds since boot.
  245  */
  246 uint64_t
  247 dtrace_gethrtime()
  248 {
  249         return (rdtsc() * (uint64_t) 1000000000 / tsc_freq);
  250 }
  251 #endif

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