/* $NetBSD: jh7110_trng.c,v 1.2 2025/02/09 09:09:49 skrll Exp $ */

/*-
 * Copyright (c) 2025 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: jh7110_trng.c,v 1.2 2025/02/09 09:09:49 skrll Exp $");

#include <sys/param.h>

#include <sys/bus.h>
#include <sys/device.h>
#include <sys/condvar.h>
#include <sys/mutex.h>
#include <sys/rndsource.h>

#include <dev/fdt/fdtvar.h>


struct jh7110_trng_softc {
        device_t                sc_dev;
        bus_space_tag_t         sc_bst;
        bus_space_handle_t      sc_bsh;
        int                     sc_phandle;

        kmutex_t                sc_lock;
        kcondvar_t              sc_cv;
        void *                  sc_ih;
        bool                    sc_reseeddone;
        size_t                  sc_bytes_wanted;

        krndsource_t            sc_rndsource;
};


#define RD4(sc, reg)                                                           \
        bus_space_read_4((sc)->sc_bst, (sc)->sc_bsh, (reg))
#define WR4(sc, reg, val)                                                      \
        bus_space_write_4((sc)->sc_bst, (sc)->sc_bsh, (reg), (val))


/* Register definitions */
// https://doc-en.rvspace.org/JH7110/TRM/JH7110_TRM/control_registers_trng.html?hl=trng
#define JH7110_TRNG_CTRL                0x0000
#define  JH7110_TRNG_CTRL_NOP                   0x0
#define  JH7110_TRNG_CTRL_RANDOMIZE             0x1
#define  JH7110_TRNG_CTRL_RANDOM_RESEED         0x2
#define  JH7110_TRNG_CTRL_NONCE_RESEED          0x3
#define JH7110_TRNG_STAT                0x0004
#define  JH7110_TRNG_STAT_SEEDED                __BIT(9)

#define JH7110_TRNG_MODE                0x0008
#define  JH7110_TRNG_MODE_R256                  __BIT(3)
#define JH7110_TRNG_SMODE               0x000c
#define JH7110_TRNG_IENABLE             0x0010
#define  JH7110_TRNG_IENABLE_GLOBAL             __BIT(31)
#define  JH7110_TRNG_IENABLE_LFSR_LOCKUP        __BIT(4)
#define  JH7110_TRNG_IENABLE_RQST_LOCKUP        __BIT(3)
#define  JH7110_TRNG_IENABLE_AGE_ALARM          __BIT(2)
#define  JH7110_TRNG_IENABLE_SEED_DONE          __BIT(1)
#define  JH7110_TRNG_IENABLE_RAND_RDY           __BIT(0)
#define JH7110_TRNG_ISTATUS             0x0014
#define  JH7110_TRNG_ISTATUS_LFSR_LOCKUP        __BIT(4)
#define  JH7110_TRNG_ISTATUS_RQST_LOCKUP        __BIT(3)
#define  JH7110_TRNG_ISTATUS_AGE_ALARM          __BIT(2)
#define  JH7110_TRNG_ISTATUS_SEED_DONE          __BIT(1)
#define  JH7110_TRNG_ISTATUS_RAND_RDY           __BIT(0)
#define JH7110_TRNG_FEATURES            0x001c
#define  JH7110_TRNG_FEATURES_MM_RESET_STATE    __BIT(3)
#define  JH7110_TRNG_FEATURES_RAND_SEED_AVAIL   __BIT(2)
#define  JH7110_TRNG_FEATURES_MAX_RAND_LENGTH   __BITS(1,0)

#define  JH7110_TRNG_FEATURES_BITS                                             \
        "\177\020"      /* New bitmask */                                      \
        "f\003\01mode reset state\0"            /* bit  3 (1) */               \
            "=\x0" "test mode\0"                                               \
            "=\x1" "mission mode\0"                                            \
        "f\002\01ring oscillator\0"             /* bit  2 (1) */               \
            "=\x0" "not preset\0"                                              \
            "=\x1" "present\0"                                                 \
        "f\000\02max rand length\0"             /* bits 0 .. 1 */              \
            "=\x0" "128-bit\0"                                                 \
            "=\x1" "256-bit\0"                                                 \
        "\0"


#define JH7110_TRNG_DATA0               0x0020
#define JH7110_TRNG_DATA1               0x0024
#define JH7110_TRNG_DATA2               0x0028
#define JH7110_TRNG_DATA3               0x002c
#define JH7110_TRNG_DATA4               0x0030
#define JH7110_TRNG_DATA5               0x0034
#define JH7110_TRNG_DATA6               0x0038
#define JH7110_TRNG_DATA7               0x003c

#define JH7110_TRNG_BCONF               0x0068
#define  JH7110_TRNG_BCONF_AUTO_RESEED_LOOPBACK __BIT(5)
#define  JH7110_TRNG_BCONF_MODE_AFTER_RST       __BIT(4)
#define  JH7110_TRNG_BCONF_PRNG_LEN_AFTER_RST   __BIT(3)
#define  JH7110_TRNG_BCONF_MAX_PRNG_LEN         __BIT(2)
#define  JH7110_TRNG_BCONF_BITS                                                \
        "\177\020"      /* New bitmask */                                      \
        "f\005\01auto reseed loopback\0"        /* bit  5 (1) */               \
            "=\x0" "not present\0"                                             \
            "=\x1" "present\0"                                                 \
        "f\004\01mode after reset\0"            /* bit  4 (1) */               \
            "=\x0" "test mode\0"                                               \
            "=\x1" "mission mode\0"                                            \
        "f\003\01PRNG after reset\0"            /* bit  3 (1) */               \
            "=\x0" "not preset\0"                                              \
            "=\x1" "present\0"                                                 \
        "f\002\01max PRNG length\0"             /* bit  2 (1) */               \
            "=\x0" "128-bit\0"                                                 \
            "=\x1" "256-bit\0"                                                 \
        "\0"


#define RD4(sc, reg)                                                           \
        bus_space_read_4((sc)->sc_bst, (sc)->sc_bsh, (reg))
#define WR4(sc, reg, val)                                                      \
        bus_space_write_4((sc)->sc_bst, (sc)->sc_bsh, (reg), (val))


static void
jh7110_trng_irqenable(struct jh7110_trng_softc *sc)
{
        WR4(sc, JH7110_TRNG_IENABLE,
            JH7110_TRNG_IENABLE_GLOBAL |
            JH7110_TRNG_IENABLE_SEED_DONE |
            JH7110_TRNG_IENABLE_RAND_RDY |
            JH7110_TRNG_IENABLE_LFSR_LOCKUP);
}

static void
jh7110_trng_irqdisable(struct jh7110_trng_softc *sc)
{
        WR4(sc, JH7110_TRNG_IENABLE, 0);
}

static void
jh7110_trng_probe(struct jh7110_trng_softc *sc, uint32_t istat)
{
        KASSERT(mutex_owned(&sc->sc_lock));

        if (sc->sc_bytes_wanted != 0) {
                uint32_t data[8];
                const uint32_t stat = RD4(sc, JH7110_TRNG_STAT);

                if (stat & JH7110_TRNG_STAT_SEEDED) {
                        if (istat & JH7110_TRNG_ISTATUS_RAND_RDY) {

                                WR4(sc, JH7110_TRNG_ISTATUS,
                                    JH7110_TRNG_ISTATUS_RAND_RDY);

                                data[0] = RD4(sc, JH7110_TRNG_DATA0);
                                data[1] = RD4(sc, JH7110_TRNG_DATA1);
                                data[2] = RD4(sc, JH7110_TRNG_DATA2);
                                data[3] = RD4(sc, JH7110_TRNG_DATA3);
                                data[4] = RD4(sc, JH7110_TRNG_DATA4);
                                data[5] = RD4(sc, JH7110_TRNG_DATA5);
                                data[6] = RD4(sc, JH7110_TRNG_DATA6);
                                data[7] = RD4(sc, JH7110_TRNG_DATA7);

                                rnd_add_data_sync(&sc->sc_rndsource, &data,
                                    sizeof(data), sizeof(data) * NBBY);

                                sc->sc_bytes_wanted -=
                                    MIN(sc->sc_bytes_wanted, sizeof(data));

                                if (sc->sc_bytes_wanted == 0)
                                        jh7110_trng_irqdisable(sc);
                        }
                } else {
                        WR4(sc, JH7110_TRNG_CTRL,
                            JH7110_TRNG_CTRL_RANDOM_RESEED);
                }
                explicit_memset(data, 0, sizeof data);
        }
        if (sc->sc_bytes_wanted != 0) {
                WR4(sc, JH7110_TRNG_CTRL,
                    JH7110_TRNG_CTRL_RANDOMIZE);
        }
}

static void
jh7110_trng_get(size_t bytes_wanted, void *arg)
{
        struct jh7110_trng_softc * const sc = arg;

        mutex_enter(&sc->sc_lock);
        sc->sc_bytes_wanted += bytes_wanted;

        jh7110_trng_irqenable(sc);

        const uint32_t istat = RD4(sc, JH7110_TRNG_ISTATUS);
        jh7110_trng_probe(sc, istat);

        mutex_exit(&sc->sc_lock);
}


static int
jh7110_trng_intr(void *priv)
{
        struct jh7110_trng_softc * const sc = priv;

        mutex_enter(&sc->sc_lock);

        const uint32_t istat = RD4(sc, JH7110_TRNG_ISTATUS);

        if (istat & JH7110_TRNG_ISTATUS_RAND_RDY) {
                KASSERT(RD4(sc, JH7110_TRNG_STAT) & JH7110_TRNG_STAT_SEEDED);
                jh7110_trng_probe(sc, istat);
                //sc->sc_randready = true;

        }

        if (istat & JH7110_TRNG_ISTATUS_SEED_DONE)
                sc->sc_reseeddone = true;

#if 0
        if (istat & JH7110_TRNG_ISTATUS_LFSR_LOCKUP) {
                sc->sc_reseeddone = false;
        }
#endif
        WR4(sc, JH7110_TRNG_ISTATUS, istat);

        if (sc->sc_reseeddone)
                cv_broadcast(&sc->sc_cv);

        mutex_exit(&sc->sc_lock);

        return 1;
}


static void
jh7110_trng_init(struct jh7110_trng_softc *sc)
{
        /* Mask and clear all interrupts. */
        WR4(sc, JH7110_TRNG_IENABLE,  0U);
        WR4(sc, JH7110_TRNG_ISTATUS, ~0U);

        WR4(sc, JH7110_TRNG_MODE, JH7110_TRNG_MODE_R256);

        mutex_enter(&sc->sc_lock);

        jh7110_trng_irqenable(sc);

        sc->sc_reseeddone = false;
        WR4(sc, JH7110_TRNG_CTRL, JH7110_TRNG_CTRL_RANDOM_RESEED);

        while (!sc->sc_reseeddone) {
                const int error = cv_timedwait(&sc->sc_cv, &sc->sc_lock, 1);
                if (error) {
                        printf("%s: timedout\n", __func__);
                        mutex_exit(&sc->sc_lock);
                        return;
                }
        }
        mutex_exit(&sc->sc_lock);
}

static void
jh7110_trng_attach_i(device_t self)
{
        struct jh7110_trng_softc * const sc = device_private(self);

        jh7110_trng_init(sc);

        /* set up an rndsource */
        rndsource_setcb(&sc->sc_rndsource, &jh7110_trng_get, sc);
        rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG,
            RND_FLAG_COLLECT_VALUE | RND_FLAG_HASCB);
}

/* Compat string(s) */
static const struct device_compatible_entry compat_data[] = {
        { .compat = "starfive,jh7110-trng" },
        DEVICE_COMPAT_EOL
};


static int
jh7110_trng_match(device_t parent, cfdata_t cf, void *aux)
{
        struct fdt_attach_args * const faa = aux;

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

static void
jh7110_trng_attach(device_t parent, device_t self, void *aux)
{
        struct jh7110_trng_softc * const sc = device_private(self);
        struct fdt_attach_args * const faa = aux;
        const int phandle = faa->faa_phandle;
        bus_space_tag_t bst = faa->faa_bst;
        bus_addr_t addr;
        bus_size_t size;
        int error;

        if (fdtbus_get_reg(phandle, 0, &addr, &size) != 0) {
                aprint_error(": couldn't get registers\n");
                return;
        }

        error = bus_space_map(bst, addr, size, 0, &sc->sc_bsh);
        if (error) {
                aprint_error(": couldn't map %#" PRIxBUSADDR ": %d", addr,
                    error);
                return;
        }

        /* Enable the hclk clock.  */
        error = fdtbus_clock_enable(phandle, "hclk", true);
        if (error) {
                aprint_error(": couldn't enable 'hclk' clock\n");
                return;
        }

        /* Enable the hclk clock.  */
        error = fdtbus_clock_enable(phandle, "ahb", true);
        if (error) {
                aprint_error(": couldn't enable 'ahb' clock\n");
                return;
        }

        /* Get a reset handle if we need and try to deassert it.  */
        struct fdtbus_reset * const rst = fdtbus_reset_get_index(phandle, 0);
        if (rst != NULL) {
                if (fdtbus_reset_deassert(rst) != 0) {
                        aprint_error(": couldn't de-assert reset\n");
                        return;
                }
        }

        sc->sc_dev = self;
        sc->sc_phandle = phandle;
        sc->sc_bst = bst;

        mutex_init(&sc->sc_lock, MUTEX_DEFAULT, IPL_VM);
        cv_init(&sc->sc_cv, "jh7110trng");

        aprint_naive("\n");
        aprint_normal(": JH7110 TRNG\n");

        char buf[256];

        snprintb(buf, sizeof(buf), JH7110_TRNG_FEATURES_BITS,
            RD4(sc, JH7110_TRNG_FEATURES));
        aprint_verbose_dev(sc->sc_dev, "Features    : %s\n", buf);

        snprintb(buf, sizeof(buf), JH7110_TRNG_BCONF_BITS,
            RD4(sc, JH7110_TRNG_BCONF));
        aprint_verbose_dev(sc->sc_dev, "Build config: %s\n", buf);

        char intrstr[128];
        if (!fdtbus_intr_str(phandle, 0, intrstr, sizeof(intrstr))) {
                aprint_error_dev(self, "failed to decode interrupt\n");
                return;
        }

        sc->sc_ih = fdtbus_intr_establish_xname(phandle, 0, IPL_VM,
            FDT_INTR_MPSAFE, jh7110_trng_intr, sc, device_xname(self));
        if (sc->sc_ih == NULL) {
                aprint_error_dev(self, "failed to establish interrupt on %s\n",
                    intrstr);
                return;
        }
        aprint_normal_dev(self, "interrupting on %s\n", intrstr);

        config_interrupts(self, jh7110_trng_attach_i);
}

CFATTACH_DECL_NEW(jh7110_trng, sizeof(struct jh7110_trng_softc),
        jh7110_trng_match, jh7110_trng_attach, NULL, NULL);