/*      $NetBSD: bcm2835_tmr.c,v 1.12 2021/01/29 14:11:14 skrll Exp $   */

/*-
 * Copyright (c) 2012 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Nick Hudson
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
__KERNEL_RCSID(0, "$NetBSD: bcm2835_tmr.c,v 1.12 2021/01/29 14:11:14 skrll Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>
#include <sys/kernel.h>
#include <sys/timetc.h>
#include <sys/bus.h>

#include <arm/broadcom/bcm2835_intr.h>
#include <arm/broadcom/bcm2835reg.h>
#include <arm/broadcom/bcm2835var.h>

#include <dev/fdt/fdtvar.h>

#include <arm/fdt/arm_fdtvar.h>

/* Use the 3rd timer*/
#define BCMTIMER        3

#define BCM2835_STIMER_CS       0x00
#define  BCM2835_STIMER_M0       __BIT(0)
#define  BCM2835_STIMER_M1       __BIT(1)
#define  BCM2835_STIMER_M2       __BIT(2)
#define  BCM2835_STIMER_M3       __BIT(3)
#define BCM2835_STIMER_CLO      0x04
#define BCM2835_STIMER_CHI      0x08
#define BCM2835_STIMER_C0       0x0c
#define BCM2835_STIMER_C1       0x10
#define BCM2835_STIMER_C2       0x14
#define BCM2835_STIMER_C3       0x18

#define BCM2835_STIMER_HZ       1000000

static const uint32_t counts_per_usec = (BCM2835_STIMER_HZ / 1000000);
static uint32_t counts_per_hz = ~0;

struct bcm2835tmr_softc {
        device_t                sc_dev;

        bus_space_tag_t sc_iot;
        bus_space_handle_t sc_ioh;

        void *sc_ih;
};

static int bcmtmr_match(device_t, cfdata_t, void *);
static void bcmtmr_attach(device_t, device_t, void *);

static int clockhandler(void *);

static u_int bcm2835tmr_get_timecount(struct timecounter *);
void bcm2835_tmr_setstatclockrate(int);

static struct bcm2835tmr_softc *bcm2835tmr_sc;

static struct timecounter bcm2835tmr_timecounter = {
        .tc_get_timecount = bcm2835tmr_get_timecount,
        .tc_poll_pps = 0,
        .tc_counter_mask = ~0u,
        .tc_frequency = BCM2835_STIMER_HZ,
        .tc_name = NULL,                        /* set by attach */
        .tc_quality = 100,
        .tc_priv = NULL,
        .tc_next = NULL,
};

CFATTACH_DECL_NEW(bcmtmr_fdt, sizeof(struct bcm2835tmr_softc),
    bcmtmr_match, bcmtmr_attach, NULL, NULL);

static const struct device_compatible_entry compat_data[] = {
        { .compat = "brcm,bcm2835-system-timer" },
        DEVICE_COMPAT_EOL
};

/* ARGSUSED */
static int
bcmtmr_match(device_t parent, cfdata_t match, void *aux)
{
        struct fdt_attach_args * const faa = aux;

        return of_compatible_match(faa->faa_phandle, compat_data);
}

static void
bcmtmr_attach(device_t parent, device_t self, void *aux)
{
        struct bcm2835tmr_softc *sc = device_private(self);
        struct fdt_attach_args * const faa = aux;

        aprint_naive("\n");
        aprint_normal(": VC System Timer\n");

        if (bcm2835tmr_sc == NULL)
                bcm2835tmr_sc = sc;

        sc->sc_dev = self;
        sc->sc_iot = faa->faa_bst;
        const int phandle = faa->faa_phandle;

        bus_addr_t addr;
        bus_size_t size;

        if (fdtbus_get_reg(phandle, 0, &addr, &size) != 0) {
                aprint_error(": missing 'reg' property\n");
                return;
        }

        if (bus_space_map(sc->sc_iot, addr, size, 0, &sc->sc_ioh) != 0) {
                aprint_error_dev(sc->sc_dev, "unable to map device\n");
                return;
        }

        char intrstr[128];
        if (!fdtbus_intr_str(phandle, BCMTIMER, intrstr, sizeof(intrstr))) {
                aprint_error(": failed to decode interrupt\n");
                return;
        }

        sc->sc_ih = fdtbus_intr_establish_xname(phandle, BCMTIMER, IPL_CLOCK,
            FDT_INTR_MPSAFE, clockhandler, NULL, device_xname(self));
        if (sc->sc_ih == NULL) {
                aprint_error(": failed to establish interrupt on %s\n",
                    intrstr);
                return;
        }
        aprint_normal_dev(self, "interrupting on %s\n", intrstr);

        bcm2835tmr_timecounter.tc_name = device_xname(self);
}

void
cpu_initclocks(void)
{
        struct bcm2835tmr_softc *sc = bcm2835tmr_sc;
        uint32_t stcl;

        KASSERT(sc != NULL);

        bcm2835tmr_timecounter.tc_priv = sc;

        counts_per_hz = BCM2835_STIMER_HZ / hz;

        stcl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_CLO);
        stcl += counts_per_hz;

        bus_space_write_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_C3, stcl);

        tc_init(&bcm2835tmr_timecounter);
}

void
bcm2835_tmr_delay(unsigned int n)
{
        struct bcm2835tmr_softc *sc = bcm2835tmr_sc;
        uint32_t last, curr;
        uint32_t delta, usecs;

        KASSERT(sc != NULL);

        last = bus_space_read_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_CLO);

        delta = usecs = 0;
        while (n > usecs) {
                curr = bus_space_read_4(sc->sc_iot, sc->sc_ioh,
                    BCM2835_STIMER_CLO);

                /* Check to see if the timer has wrapped around. */
                if (curr < last)
                        delta += curr + (UINT32_MAX - last);
                else
                        delta += curr - last;

                last = curr;

                if (delta >= counts_per_usec) {
                        usecs += delta / counts_per_usec;
                        delta %= counts_per_usec;
                }
        }
}

/*
 * clockhandler:
 *
 *      Handle the hardclock interrupt.
 */
static int
clockhandler(void *arg)
{
        struct bcm2835tmr_softc *sc = bcm2835tmr_sc;
        struct clockframe *frame = arg;
        uint32_t curr, status;

        status = bus_space_read_4(sc->sc_iot, sc->sc_ioh,
            BCM2835_STIMER_CS);

        if (!(status & BCM2835_STIMER_M3))
                return 0;

        bus_space_write_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_CS,
            BCM2835_STIMER_M3);

        hardclock(frame);

        curr = bus_space_read_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_CLO);

        curr += counts_per_hz;
        bus_space_write_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_C3, curr);

        return 1;
}

void
setstatclockrate(int newhz)
{
}

static u_int
bcm2835tmr_get_timecount(struct timecounter *tc)
{
        struct bcm2835tmr_softc *sc = tc->tc_priv;

        return bus_space_read_4(sc->sc_iot, sc->sc_ioh, BCM2835_STIMER_CLO);
}