FreeBSD/Linux Kernel Cross Reference
sys/dev/efidev/efirtc.c

     /*-
      * Copyright (c) 2017 Andrew Turner
      * All rights reserved.
      *
      * This software was developed by SRI International and the University of
      * Cambridge Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
      * ("CTSRD"), as part of the DARPA CRASH research programme.
      *
      * 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 <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/clock.h>
    #include <sys/efi.h>
    #include <sys/kernel.h>
    #include <sys/module.h>
    
    #include "clock_if.h"
    
    static bool efirtc_zeroes_subseconds;
    static struct timespec efirtc_resadj;
    
    static const u_int us_per_s  = 1000000;
    static const u_int ns_per_s  = 1000000000;
    static const u_int ns_per_us = 1000;
    
    static void
    efirtc_identify(driver_t *driver, device_t parent)
    {
    
            /* Don't add the driver unless we have working runtime services. */
            if (efi_rt_ok() != 0)
                    return;
            if (device_find_child(parent, "efirtc", -1) != NULL)
                    return;
            if (BUS_ADD_CHILD(parent, 0, "efirtc", -1) == NULL)
                    device_printf(parent, "add child failed\n");
    }
    
    static int
    efirtc_probe(device_t dev)
    {
            struct efi_tm tm;
            int error;
    
            /*
             * Check whether we can read the time.  This will stop us from attaching
             * when there is EFI Runtime support but the gettime function is
             * unimplemented, e.g. on some builds of U-Boot.
             */
            if ((error = efi_get_time(&tm)) != 0) {
                    if (bootverbose)
                            device_printf(dev, "cannot read EFI realtime clock, "
                                "error %d\n", error);
                    return (error);
            }
            device_set_desc(dev, "EFI Realtime Clock");
            return (BUS_PROBE_DEFAULT);
    }
    
    static int
    efirtc_attach(device_t dev)
    {
            struct efi_tmcap tmcap;
            long res;
            int error;
    
            bzero(&tmcap, sizeof(tmcap));
            if ((error = efi_get_time_capabilities(&tmcap)) != 0) {
                    device_printf(dev, "cannot get EFI time capabilities");
                    return (error);
            }
    
            /* Translate resolution in Hz to tick length in usec. */
            if (tmcap.tc_res == 0)
                   res = us_per_s; /* 0 is insane, assume 1 Hz. */
           else if (tmcap.tc_res > us_per_s)
                   res = 1; /* 1us is the best we can represent */
           else
                   res = us_per_s / tmcap.tc_res;
   
           /* Clock rounding adjustment is 1/2 of resolution, in nsec. */
           efirtc_resadj.tv_nsec = (res * ns_per_us) / 2;
   
           /* Does the clock zero the subseconds when time is set? */
           efirtc_zeroes_subseconds = tmcap.tc_stz;
   
           /*
            * Register.  If the clock zeroes out the subseconds when it's set,
            * schedule the SetTime calls to happen just before top-of-second.
            */
           clock_register_flags(dev, res, CLOCKF_SETTIME_NO_ADJ);
           if (efirtc_zeroes_subseconds)
                   clock_schedule(dev, ns_per_s - ns_per_us);
   
           return (0);
   }
   
   static int
   efirtc_detach(device_t dev)
   {
   
           clock_unregister(dev);
           return (0);
   }
   
   static int
   efirtc_gettime(device_t dev, struct timespec *ts)
   {
           struct clocktime ct;
           struct efi_tm tm;
           int error;
   
           error = efi_get_time(&tm);
           if (error != 0)
                   return (error);
   
           ct.sec = tm.tm_sec;
           ct.min = tm.tm_min;
           ct.hour = tm.tm_hour;
           ct.day = tm.tm_mday;
           ct.mon = tm.tm_mon;
           ct.year = tm.tm_year;
           ct.nsec = tm.tm_nsec;
   
           clock_dbgprint_ct(dev, CLOCK_DBG_READ, &ct);
           return (clock_ct_to_ts(&ct, ts));
   }
   
   static int
   efirtc_settime(device_t dev, struct timespec *ts)
   {
           struct clocktime ct;
           struct efi_tm tm;
   
           /*
            * We request a timespec with no resolution-adjustment so that we can
            * apply it ourselves based on whether or not the clock zeroes the
            * sub-second part of the time when setting the time.
            */
           ts->tv_sec -= utc_offset();
           if (!efirtc_zeroes_subseconds)
                   timespecadd(ts, &efirtc_resadj, ts);
           
           clock_ts_to_ct(ts, &ct);
           clock_dbgprint_ct(dev, CLOCK_DBG_WRITE, &ct);
   
           bzero(&tm, sizeof(tm));
           tm.tm_sec = ct.sec;
           tm.tm_min = ct.min;
           tm.tm_hour = ct.hour;
           tm.tm_mday = ct.day;
           tm.tm_mon = ct.mon;
           tm.tm_year = ct.year;
           tm.tm_nsec = ct.nsec;
   
           return (efi_set_time(&tm));
   }
   
   static device_method_t efirtc_methods[] = {
           /* Device interface */
           DEVMETHOD(device_identify,      efirtc_identify),
           DEVMETHOD(device_probe,         efirtc_probe),
           DEVMETHOD(device_attach,        efirtc_attach),
           DEVMETHOD(device_detach,        efirtc_detach),
   
           /* Clock interface */
           DEVMETHOD(clock_gettime,        efirtc_gettime),
           DEVMETHOD(clock_settime,        efirtc_settime),
   
           DEVMETHOD_END
   };
   
   static driver_t efirtc_driver = {
           "efirtc",
           efirtc_methods,
           0
   };
   
   DRIVER_MODULE(efirtc, nexus, efirtc_driver, 0, 0);
   MODULE_VERSION(efirtc, 1);
   MODULE_DEPEND(efirtc, efirt, 1, 1, 1);

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