FreeBSD/Linux Kernel Cross Reference
sys/arm/freescale/imx/imx6_snvs.c

     /*-
      * Copyright (c) 2017 Ian Lepore <ian@freebsd.org>
      * All rights reserved.
      *
      * 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("$FreeBSD$");
    
    /*
     * Driver for imx6 Secure Non-Volatile Storage system, which really means "all
     * the stuff that's powered by a battery when main power is off".  This includes
     * realtime clock, tamper monitor, and power-management functions.  Currently
     * this driver provides only realtime clock support.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bus.h>
    #include <sys/clock.h>
    #include <sys/kernel.h>
    #include <sys/module.h>
    #include <machine/bus.h>
    
    #include <dev/ofw/ofw_bus_subr.h>
    
    #include "clock_if.h"
    
    #define SNVS_LPCR               0x38            /* Control register */
    #define   LPCR_LPCALB_VAL_SHIFT   10            /* Calibration shift */
    #define   LPCR_LPCALB_VAL_MASK    0x1f          /* Calibration mask */
    #define   LPCR_LPCALB_EN          (1u << 8)     /* Calibration enable */
    #define   LPCR_SRTC_ENV           (1u << 0)     /* RTC enabled/valid */
    
    #define SNVS_LPSRTCMR           0x50            /* Counter MSB */
    #define SNVS_LPSRTCLR           0x54            /* Counter LSB */
    
    #define RTC_RESOLUTION_US       (1000000 / 32768) /* 32khz clock */
    
    /*
     * The RTC is a 47-bit counter clocked at 32KHz and organized as a 32.15
     * fixed-point binary value.  Shifting by SBT_LSB bits translates between
     * counter and sbintime values.
     */
    #define RTC_BITS        47
    #define SBT_BITS        64
    #define SBT_LSB         (SBT_BITS - RTC_BITS)
    
    struct snvs_softc {
            device_t                dev;
            struct resource *       memres;
            uint32_t                lpcr;
    };
    
    static struct ofw_compat_data compat_data[] = {
            {"fsl,sec-v4.0-mon-rtc-lp", true},
            {"fsl,sec-v4.0-mon", true},
            {NULL,               false}
    };
    
    static inline uint32_t
    RD4(struct snvs_softc *sc, bus_size_t offset)
    {
    
            return (bus_read_4(sc->memres, offset));
    }
    
    static inline void
    WR4(struct snvs_softc *sc, bus_size_t offset, uint32_t value)
    {
    
            bus_write_4(sc->memres, offset, value);
    }
    
    static void
    snvs_rtc_enable(struct snvs_softc *sc, bool enable)
    {
            uint32_t enbit;
    
           if (enable)
                   sc->lpcr |= LPCR_SRTC_ENV;
           else
                   sc->lpcr &= ~LPCR_SRTC_ENV;
           WR4(sc, SNVS_LPCR, sc->lpcr);
   
           /* Wait for the hardware to achieve the requested state. */
           enbit = sc->lpcr & LPCR_SRTC_ENV;
           while ((RD4(sc, SNVS_LPCR) & LPCR_SRTC_ENV) != enbit)
                   continue;
   }
   
   static int
   snvs_gettime(device_t dev, struct timespec *ts)
   {
           struct snvs_softc *sc;
           sbintime_t counter1, counter2;
   
           sc = device_get_softc(dev);
   
           /* If the clock is not enabled and valid, we can't help. */
           if (!(RD4(sc, SNVS_LPCR) & LPCR_SRTC_ENV)) {
                   return (EINVAL);
           }
   
           /*
            * The counter is clocked asynchronously to cpu accesses; read and
            * assemble the pieces of the counter until we get the same value twice.
            * The counter is 47 bits, organized as a 32.15 binary fixed-point
            * value. If we shift it up to the high order part of a 64-bit word it
            * turns into an sbintime.
            */
           do {
                   counter1  = (uint64_t)RD4(sc, SNVS_LPSRTCMR) << (SBT_LSB + 32);
                   counter1 |= (uint64_t)RD4(sc, SNVS_LPSRTCLR) << (SBT_LSB);
                   counter2  = (uint64_t)RD4(sc, SNVS_LPSRTCMR) << (SBT_LSB + 32);
                   counter2 |= (uint64_t)RD4(sc, SNVS_LPSRTCLR) << (SBT_LSB);
           } while (counter1 != counter2);
   
           *ts = sbttots(counter1);
   
           clock_dbgprint_ts(sc->dev, CLOCK_DBG_READ, ts); 
   
           return (0);
   }
   
   static int
   snvs_settime(device_t dev, struct timespec *ts)
   {
           struct snvs_softc *sc;
           sbintime_t sbt;
   
           sc = device_get_softc(dev);
   
           /*
            * The hardware format is the same as sbt (with fewer fractional bits),
            * so first convert the time to sbt.  It takes two clock cycles for the
            * counter to start after setting the enable bit, so add two SBT_LSBs to
            * what we're about to set.
            */
           sbt = tstosbt(*ts);
           sbt += 2 << SBT_LSB;
           snvs_rtc_enable(sc, false);
           WR4(sc, SNVS_LPSRTCMR, (uint32_t)(sbt >> (SBT_LSB + 32)));
           WR4(sc, SNVS_LPSRTCLR, (uint32_t)(sbt >> (SBT_LSB)));
           snvs_rtc_enable(sc, true);
   
           clock_dbgprint_ts(sc->dev, CLOCK_DBG_WRITE, ts); 
   
           return (0);
   }
   
   static int
   snvs_probe(device_t dev)
   {
   
           if (!ofw_bus_status_okay(dev))
                   return (ENXIO);
   
           if (!ofw_bus_search_compatible(dev, compat_data)->ocd_data)
                   return (ENXIO);
   
           device_set_desc(dev, "i.MX6 SNVS RTC");
           return (BUS_PROBE_DEFAULT);
   }
   
   static int
   snvs_attach(device_t dev)
   {
           struct snvs_softc *sc;
           int rid;
   
           sc = device_get_softc(dev);
           sc->dev = dev;
   
           rid = 0;
           sc->memres = bus_alloc_resource_any(sc->dev, SYS_RES_MEMORY, &rid,
               RF_ACTIVE);
           if (sc->memres == NULL) {
                   device_printf(sc->dev, "could not allocate registers\n");
                   return (ENXIO);
           }
   
           clock_register(sc->dev, RTC_RESOLUTION_US);
   
           return (0);
   }
   
   static int
   snvs_detach(device_t dev)
   {
           struct snvs_softc *sc;
   
           sc = device_get_softc(dev);
           clock_unregister(sc->dev);
           bus_release_resource(sc->dev, SYS_RES_MEMORY, 0, sc->memres);
           return (0);
   }
   
   static device_method_t snvs_methods[] = {
           DEVMETHOD(device_probe,         snvs_probe),
           DEVMETHOD(device_attach,        snvs_attach),
           DEVMETHOD(device_detach,        snvs_detach),
   
           /* clock_if methods */
           DEVMETHOD(clock_gettime,        snvs_gettime),
           DEVMETHOD(clock_settime,        snvs_settime),
   
           DEVMETHOD_END
   };
   
   static driver_t snvs_driver = {
           "snvs",
           snvs_methods,
           sizeof(struct snvs_softc),
   };
   
   static devclass_t snvs_devclass;
   
   DRIVER_MODULE(snvs, simplebus, snvs_driver, snvs_devclass, 0, 0);
   SIMPLEBUS_PNP_INFO(compat_data);

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