FreeBSD/Linux Kernel Cross Reference
sys/dev/goldfish/goldfish_rtc.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2020 Jessica Clarke <jrtc27@FreeBSD.org>
      *
      * 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.
     */
    
    /*
     * RTC for the goldfish virtual hardware platform implemented in QEMU,
     * initially for Android but now also used for RISC-V's virt machine.
     *
     * https://android.googlesource.com/platform/external/qemu/+/master/docs/GOLDFISH-VIRTUAL-HARDWARE.TXT
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/clock.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/module.h>
    #include <sys/mutex.h>
    #include <sys/types.h>
    
    #include <dev/ofw/ofw_bus.h>
    #include <dev/ofw/ofw_bus_subr.h>
    
    #include <machine/bus.h>
    #include <machine/resource.h>
    #include <sys/rman.h>
    
    #include "clock_if.h"
    
    #define GOLDFISH_RTC_TIME_LOW   0x00
    #define GOLDFISH_RTC_TIME_HIGH  0x04
    
    struct goldfish_rtc_softc {
            struct resource *res;
            int             rid;
            struct mtx      mtx;
    };
    
    static int
    goldfish_rtc_probe(device_t dev)
    {
    
            if (!ofw_bus_status_okay(dev))
                    return (ENXIO);
    
            if (ofw_bus_is_compatible(dev, "google,goldfish-rtc")) {
                    device_set_desc(dev, "Goldfish RTC");
                    return (BUS_PROBE_DEFAULT);
            }
    
            return (ENXIO);
    }
    
    static int
    goldfish_rtc_attach(device_t dev)
    {
            struct goldfish_rtc_softc *sc;
    
            sc = device_get_softc(dev);
    
            sc->rid = 0;
            sc->res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &sc->rid,
                RF_ACTIVE);
            if (sc->res == NULL) {
                    device_printf(dev, "could not allocate resource\n");
                    return (ENXIO);
            }
    
            mtx_init(&sc->mtx, device_get_nameunit(dev), NULL, MTX_DEF);
    
            /*
             * Register as a system realtime clock with 1 second resolution.
            */
           clock_register_flags(dev, 1000000, CLOCKF_SETTIME_NO_ADJ);
           clock_schedule(dev, 1);
   
           return (0);
   }
   
   static int
   goldfish_rtc_detach(device_t dev)
   {
           struct goldfish_rtc_softc *sc;
   
           sc = device_get_softc(dev);
   
           clock_unregister(dev);
           mtx_destroy(&sc->mtx);
           bus_release_resource(dev, SYS_RES_MEMORY, sc->rid, sc->res);
   
           return (0);
   }
   
   static int
   goldfish_rtc_gettime(device_t dev, struct timespec *ts)
   {
           struct goldfish_rtc_softc *sc;
           uint64_t low, high, nsec;
   
           sc = device_get_softc(dev);
   
           /*
            * Reading TIME_HIGH is defined in the documentation to give the high
            * 32 bits corresponding to the last TIME_LOW read, so must be done in
            * that order, but means we have atomicity guaranteed.
            */
           mtx_lock(&sc->mtx);
           low = bus_read_4(sc->res, GOLDFISH_RTC_TIME_LOW);
           high = bus_read_4(sc->res, GOLDFISH_RTC_TIME_HIGH);
           mtx_unlock(&sc->mtx);
   
           nsec = (high << 32) | low;
           ts->tv_sec = nsec / 1000000000;
           ts->tv_nsec = nsec % 1000000000;
   
           return (0);
   }
   
   static int
   goldfish_rtc_settime(device_t dev, struct timespec *ts)
   {
           struct goldfish_rtc_softc *sc;
           uint64_t nsec;
   
           sc = device_get_softc(dev);
   
           /*
            * We request a timespec with no resolution-adjustment.  That also
            * disables utc adjustment, so apply that ourselves.
            */
           ts->tv_sec -= utc_offset();
           nsec = (uint64_t)ts->tv_sec * 1000000000 + ts->tv_nsec;
   
           mtx_lock(&sc->mtx);
           bus_write_4(sc->res, GOLDFISH_RTC_TIME_HIGH, nsec >> 32);
           bus_write_4(sc->res, GOLDFISH_RTC_TIME_LOW, nsec);
           mtx_unlock(&sc->mtx);
   
           return (0);
   }
   
   static device_method_t goldfish_rtc_methods[] = {
           /* Device interface */
           DEVMETHOD(device_probe,         goldfish_rtc_probe),
           DEVMETHOD(device_attach,        goldfish_rtc_attach),
           DEVMETHOD(device_detach,        goldfish_rtc_detach),
   
           /* Clock interface */
           DEVMETHOD(clock_gettime,        goldfish_rtc_gettime),
           DEVMETHOD(clock_settime,        goldfish_rtc_settime),
   
           DEVMETHOD_END,
   };
   
   DEFINE_CLASS_0(goldfish_rtc, goldfish_rtc_driver, goldfish_rtc_methods,
       sizeof(struct goldfish_rtc_softc));
   
   DRIVER_MODULE(goldfish_rtc, simplebus, goldfish_rtc_driver, NULL, NULL);

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