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/mips/nlm/tick.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright 2003-2011 Netlogic Microsystems (Netlogic). All rights
    5  * reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions are
    9  * met:
   10  *
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in
   15  *    the documentation and/or other materials provided with the
   16  *    distribution.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY Netlogic Microsystems ``AS IS'' AND
   19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   21  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NETLOGIC OR CONTRIBUTORS BE
   22  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   24  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   25  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   26  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
   28  * THE POSSIBILITY OF SUCH DAMAGE.
   29  *
   30  * NETLOGIC_BSD */
   31 
   32 /*
   33  * Simple driver for the 32-bit interval counter built in to all
   34  * MIPS32 CPUs.
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: stable/12/sys/mips/nlm/tick.c 336007 2018-07-05 17:13:37Z andrew $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/sysctl.h>
   43 #include <sys/bus.h>
   44 #include <sys/kernel.h>
   45 #include <sys/module.h>
   46 #include <sys/rman.h>
   47 #include <sys/power.h>
   48 #include <sys/smp.h>
   49 #include <sys/time.h>
   50 #include <sys/timeet.h>
   51 #include <sys/timetc.h>
   52 
   53 #include <machine/hwfunc.h>
   54 #include <machine/clock.h>
   55 #include <machine/locore.h>
   56 #include <machine/md_var.h>
   57 #include <machine/intr_machdep.h>
   58 
   59 #include <mips/nlm/interrupt.h>
   60 
   61 uint64_t counter_freq;
   62 
   63 struct timecounter *platform_timecounter;
   64 
   65 DPCPU_DEFINE_STATIC(uint32_t, cycles_per_tick);
   66 static uint32_t cycles_per_usec;
   67 
   68 DPCPU_DEFINE_STATIC(volatile uint32_t, counter_upper);
   69 DPCPU_DEFINE_STATIC(volatile uint32_t, counter_lower_last);
   70 DPCPU_DEFINE_STATIC(uint32_t, compare_ticks);
   71 DPCPU_DEFINE_STATIC(uint32_t, lost_ticks);
   72 
   73 struct clock_softc {
   74         int intr_rid;
   75         struct resource *intr_res;
   76         void *intr_handler;
   77         struct timecounter tc;
   78         struct eventtimer et;
   79 };
   80 static struct clock_softc *softc;
   81 
   82 /*
   83  * Device methods
   84  */
   85 static int clock_probe(device_t);
   86 static void clock_identify(driver_t *, device_t);
   87 static int clock_attach(device_t);
   88 static unsigned counter_get_timecount(struct timecounter *tc);
   89 
   90 void
   91 mips_timer_early_init(uint64_t clock_hz)
   92 {
   93         /* Initialize clock early so that we can use DELAY sooner */
   94         counter_freq = clock_hz;
   95         cycles_per_usec = (clock_hz / (1000 * 1000));
   96 }
   97 
   98 void
   99 platform_initclocks(void)
  100 {
  101 
  102         if (platform_timecounter != NULL)
  103                 tc_init(platform_timecounter);
  104 }
  105 
  106 static uint64_t
  107 tick_ticker(void)
  108 {
  109         uint64_t ret;
  110         uint32_t ticktock;
  111         uint32_t t_lower_last, t_upper;
  112 
  113         /*
  114          * Disable preemption because we are working with cpu specific data.
  115          */
  116         critical_enter();
  117 
  118         /*
  119          * Note that even though preemption is disabled, interrupts are
  120          * still enabled. In particular there is a race with clock_intr()
  121          * reading the values of 'counter_upper' and 'counter_lower_last'.
  122          *
  123          * XXX this depends on clock_intr() being executed periodically
  124          * so that 'counter_upper' and 'counter_lower_last' are not stale.
  125          */
  126         do {
  127                 t_upper = DPCPU_GET(counter_upper);
  128                 t_lower_last = DPCPU_GET(counter_lower_last);
  129         } while (t_upper != DPCPU_GET(counter_upper));
  130 
  131         ticktock = mips_rd_count();
  132 
  133         critical_exit();
  134 
  135         /* COUNT register wrapped around */
  136         if (ticktock < t_lower_last)
  137                 t_upper++;
  138 
  139         ret = ((uint64_t)t_upper << 32) | ticktock;
  140         return (ret);
  141 }
  142 
  143 void
  144 mips_timer_init_params(uint64_t platform_counter_freq, int double_count)
  145 {
  146 
  147         /*
  148          * XXX: Do not use printf here: uart code 8250 may use DELAY so this
  149          * function should  be called before cninit.
  150          */
  151         counter_freq = platform_counter_freq;
  152         /*
  153          * XXX: Some MIPS32 cores update the Count register only every two
  154          * pipeline cycles.
  155          * We know this because of status registers in CP0, make it automatic.
  156          */
  157         if (double_count != 0)
  158                 counter_freq /= 2;
  159 
  160         cycles_per_usec = counter_freq / (1 * 1000 * 1000);
  161         set_cputicker(tick_ticker, counter_freq, 1);
  162 }
  163 
  164 static int
  165 sysctl_machdep_counter_freq(SYSCTL_HANDLER_ARGS)
  166 {
  167         int error;
  168         uint64_t freq;
  169 
  170         if (softc == NULL)
  171                 return (EOPNOTSUPP);
  172         freq = counter_freq;
  173         error = sysctl_handle_64(oidp, &freq, sizeof(freq), req);
  174         if (error == 0 && req->newptr != NULL) {
  175                 counter_freq = freq;
  176                 softc->et.et_frequency = counter_freq;
  177                 softc->tc.tc_frequency = counter_freq;
  178         }
  179         return (error);
  180 }
  181 
  182 SYSCTL_PROC(_machdep, OID_AUTO, counter_freq, CTLTYPE_U64 | CTLFLAG_RW,
  183     NULL, 0, sysctl_machdep_counter_freq, "QU",
  184     "Timecounter frequency in Hz");
  185 
  186 static unsigned
  187 counter_get_timecount(struct timecounter *tc)
  188 {
  189 
  190         return (mips_rd_count());
  191 }
  192 
  193 /*
  194  * Wait for about n microseconds (at least!).
  195  */
  196 void
  197 DELAY(int n)
  198 {
  199         uint32_t cur, last, delta, usecs;
  200 
  201         TSENTER();
  202         /*
  203          * This works by polling the timer and counting the number of
  204          * microseconds that go by.
  205          */
  206         last = mips_rd_count();
  207         delta = usecs = 0;
  208 
  209         while (n > usecs) {
  210                 cur = mips_rd_count();
  211 
  212                 /* Check to see if the timer has wrapped around. */
  213                 if (cur < last)
  214                         delta += cur + (0xffffffff - last) + 1;
  215                 else
  216                         delta += cur - last;
  217 
  218                 last = cur;
  219 
  220                 if (delta >= cycles_per_usec) {
  221                         usecs += delta / cycles_per_usec;
  222                         delta %= cycles_per_usec;
  223                 }
  224         }
  225         TSEXIT();
  226 }
  227 
  228 static int
  229 clock_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
  230 {
  231         uint32_t fdiv, div, next;
  232 
  233         if (period != 0)
  234                 div = (et->et_frequency * period) >> 32;
  235         else
  236                 div = 0;
  237         if (first != 0)
  238                 fdiv = (et->et_frequency * first) >> 32;
  239         else
  240                 fdiv = div;
  241         DPCPU_SET(cycles_per_tick, div);
  242         next = mips_rd_count() + fdiv;
  243         DPCPU_SET(compare_ticks, next);
  244         mips_wr_compare(next);
  245         return (0);
  246 }
  247 
  248 static int
  249 clock_stop(struct eventtimer *et)
  250 {
  251 
  252         DPCPU_SET(cycles_per_tick, 0);
  253         mips_wr_compare(0xffffffff);
  254         return (0);
  255 }
  256 
  257 /*
  258  * Device section of file below
  259  */
  260 static int
  261 clock_intr(void *arg)
  262 {
  263         struct clock_softc *sc = (struct clock_softc *)arg;
  264         uint32_t cycles_per_tick;
  265         uint32_t count, compare_last, compare_next, lost_ticks;
  266 
  267         cycles_per_tick = DPCPU_GET(cycles_per_tick);
  268         /*
  269          * Set next clock edge.
  270          */
  271         count = mips_rd_count();
  272         compare_last = DPCPU_GET(compare_ticks);
  273         if (cycles_per_tick > 0) {
  274                 compare_next = count + cycles_per_tick;
  275                 DPCPU_SET(compare_ticks, compare_next);
  276                 mips_wr_compare(compare_next);
  277         } else  /* In one-shot mode timer should be stopped after the event. */
  278                 mips_wr_compare(0xffffffff);
  279 
  280         /* COUNT register wrapped around */
  281         if (count < DPCPU_GET(counter_lower_last)) {
  282                 DPCPU_SET(counter_upper, DPCPU_GET(counter_upper) + 1);
  283         }
  284         DPCPU_SET(counter_lower_last, count);
  285 
  286         if (cycles_per_tick > 0) {
  287 
  288                 /*
  289                  * Account for the "lost time" between when the timer interrupt
  290                  * fired and when 'clock_intr' actually started executing.
  291                  */
  292                 lost_ticks = DPCPU_GET(lost_ticks);
  293                 lost_ticks += count - compare_last;
  294 
  295                 /*
  296                  * If the COUNT and COMPARE registers are no longer in sync
  297                  * then make up some reasonable value for the 'lost_ticks'.
  298                  *
  299                  * This could happen, for e.g., after we resume normal
  300                  * operations after exiting the debugger.
  301                  */
  302                 if (lost_ticks > 2 * cycles_per_tick)
  303                         lost_ticks = cycles_per_tick;
  304 
  305                 while (lost_ticks >= cycles_per_tick) {
  306                         if (sc->et.et_active)
  307                                 sc->et.et_event_cb(&sc->et, sc->et.et_arg);
  308                         lost_ticks -= cycles_per_tick;
  309                 }
  310                 DPCPU_SET(lost_ticks, lost_ticks);
  311         }
  312         if (sc->et.et_active)
  313                 sc->et.et_event_cb(&sc->et, sc->et.et_arg);
  314         return (FILTER_HANDLED);
  315 }
  316 
  317 static int
  318 clock_probe(device_t dev)
  319 {
  320 
  321         device_set_desc(dev, "Generic MIPS32 ticker");
  322         return (BUS_PROBE_NOWILDCARD);
  323 }
  324 
  325 static void
  326 clock_identify(driver_t * drv, device_t parent)
  327 {
  328 
  329         BUS_ADD_CHILD(parent, 0, "clock", 0);
  330 }
  331 
  332 static int
  333 clock_attach(device_t dev)
  334 {
  335         struct clock_softc *sc;
  336 
  337         if (device_get_unit(dev) != 0)
  338                 panic("can't attach more clocks");
  339 
  340         softc = sc = device_get_softc(dev);
  341         cpu_establish_hardintr("compare", clock_intr, NULL,
  342             sc, IRQ_TIMER, INTR_TYPE_CLK, &sc->intr_handler);
  343 
  344         sc->tc.tc_get_timecount = counter_get_timecount;
  345         sc->tc.tc_counter_mask = 0xffffffff;
  346         sc->tc.tc_frequency = counter_freq;
  347         sc->tc.tc_name = "MIPS32";
  348         sc->tc.tc_quality = 800;
  349         sc->tc.tc_priv = sc;
  350         tc_init(&sc->tc);
  351         sc->et.et_name = "MIPS32";
  352 #if 0
  353         sc->et.et_flags = ET_FLAGS_PERIODIC | ET_FLAGS_ONESHOT |
  354             ET_FLAGS_PERCPU;
  355 #endif
  356         sc->et.et_flags = ET_FLAGS_PERIODIC | ET_FLAGS_PERCPU;
  357         sc->et.et_quality = 800;
  358         sc->et.et_frequency = counter_freq;
  359         sc->et.et_min_period = 0x00004000LLU; /* To be safe. */
  360         sc->et.et_max_period = (0xfffffffeLLU << 32) / sc->et.et_frequency;
  361         sc->et.et_start = clock_start;
  362         sc->et.et_stop = clock_stop;
  363         sc->et.et_priv = sc;
  364         et_register(&sc->et);
  365         return (0);
  366 }
  367 
  368 static device_method_t clock_methods[] = {
  369         /* Device interface */
  370         DEVMETHOD(device_probe, clock_probe),
  371         DEVMETHOD(device_identify, clock_identify),
  372         DEVMETHOD(device_attach, clock_attach),
  373         DEVMETHOD(device_detach, bus_generic_detach),
  374         DEVMETHOD(device_shutdown, bus_generic_shutdown),
  375 
  376         {0, 0}
  377 };
  378 
  379 static driver_t clock_driver = {
  380         "clock",
  381         clock_methods,
  382         sizeof(struct clock_softc),
  383 };
  384 
  385 static devclass_t clock_devclass;
  386 
  387 DRIVER_MODULE(clock, nexus, clock_driver, clock_devclass, 0, 0);

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