/*      $NetBSD: fwhrng.c,v 1.9 2015/04/13 16:03:51 riastradh Exp $     */

/*
* Copyright (c) 2000 Michael Shalayeff
* 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 ``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 HIS RELATIVES 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 MIND, 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.
*
*      from OpenBSD: pchb.c,v 1.23 2000/10/23 20:07:30 deraadt Exp
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: fwhrng.c,v 1.9 2015/04/13 16:03:51 riastradh Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>
#include <sys/time.h>
#include <sys/rndsource.h>

#include <sys/bus.h>

#include <arch/x86/pci/i82802reg.h>

struct fwhrng_softc {
       device_t sc_dev;

       bus_space_tag_t sc_st;
       bus_space_handle_t sc_sh;

       struct callout sc_rnd_ch;
       krndsource_t sc_rnd_source;

       int sc_rnd_i;
       uint32_t sc_rnd_ax;
};

static int fwhrng_match(device_t, cfdata_t, void *);
static void fwhrng_attach(device_t, device_t, void *);
static int fwhrng_detach(device_t, int);

static void fwhrng_callout(void *v);

#define FWHRNG_RETRIES          1000
#define FWHRNG_MIN_SAMPLES      10

CFATTACH_DECL_NEW(fwhrng, sizeof(struct fwhrng_softc),
   fwhrng_match, fwhrng_attach, fwhrng_detach, NULL);

static int
fwhrng_match(device_t parent, cfdata_t match, void *aux)
{
       bus_space_tag_t bst;
       bus_space_handle_t bsh;
       uint8_t id0, id1, data0, data1;

       bst = x86_bus_space_mem;

       /* read chip ID */
       if (bus_space_map(bst, I82802AB_MEMBASE, I82802AB_WINSIZE, 0, &bsh))
               return 0;

       bus_space_write_1(bst, bsh, 0, 0xff); /* reset */
       data0 = bus_space_read_1(bst, bsh, 0);
       data1 = bus_space_read_1(bst, bsh, 1);
       bus_space_write_1(bst, bsh, 0, 0x90); /* enter read id */
       id0 = bus_space_read_1(bst, bsh, 0);
       id1 = bus_space_read_1(bst, bsh, 1);
       bus_space_write_1(bst, bsh, 0, 0xff); /* reset */

       bus_space_unmap(bst, bsh, I82802AB_WINSIZE);

       aprint_debug_dev(parent, "fwh: data %02x,%02x, id %02x,%02x\n",
           data0, data1, id0, id1);

       /* unlikely to have these match if we actually read the ID */
       if ((id0 == data0) && (id1 == data1))
               return 0;

       /* check for chips with RNG */
       if (!(id0 == I82802_MFG))
               return 0;
       if (!((id1 == I82802AB_ID) || (id1 == I82802AC_ID)))
               return 0;

       /* check for RNG presence */
       if (bus_space_map(bst, I82802AC_REGBASE, I82802AC_WINSIZE, 0, &bsh))
               return 0;
       data0 = bus_space_read_1(bst, bsh, I82802_RNG_HSR);
       bus_space_unmap(bst, bsh, I82802AC_WINSIZE);
       if ((data0 & I82802_RNG_HSR_PRESENT) == I82802_RNG_HSR_PRESENT)
               return 1;

       return 0;
}

static void
fwhrng_attach(device_t parent, device_t self, void *aux)
{
       struct fwhrng_softc *sc;
       int i, j, count_ff;
       uint8_t reg8;

       sc = device_private(self);
       sc->sc_dev = self;

       aprint_naive("\n");
       aprint_normal(": Intel Firmware Hub Random Number Generator\n");

       sc->sc_st = x86_bus_space_mem;

       if (bus_space_map(sc->sc_st, I82802AC_REGBASE, I82802AC_WINSIZE, 0,
           &sc->sc_sh) != 0) {
               aprint_error_dev(self, "unable to map registers\n");
               return;
       }

       /* Enable the RNG. */
       reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR);
       bus_space_write_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR,
           reg8 | I82802_RNG_HSR_ENABLE);
       reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR);
       if ((reg8 & I82802_RNG_HSR_ENABLE) == 0) {
               aprint_error_dev(self, "unable to enable\n");
               bus_space_unmap(sc->sc_st, sc->sc_sh, I82802AC_WINSIZE);
               return;
       }

       /* Check to see if we can read data from the RNG. */
       count_ff = 0;
       for (j = 0; j < FWHRNG_MIN_SAMPLES; ++j) {
               for (i = 0; i < FWHRNG_RETRIES; i++) {
                       reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh,
                           I82802_RNG_DSR);
                       if (!(reg8 & I82802_RNG_DSR_VALID)) {
                               delay(10);
                               continue;
                       }
                       reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh,
                           I82802_RNG_DR);
                       break;
               }
               if (i == FWHRNG_RETRIES) {
                       bus_space_unmap(sc->sc_st, sc->sc_sh, I82802AC_WINSIZE);
                       aprint_verbose_dev(sc->sc_dev,
                           "timeout reading test samples, RNG disabled.\n");
                       return;
               }
               if (reg8 == 0xff)
                       ++count_ff;
       }

       if (count_ff == FWHRNG_MIN_SAMPLES) {
               /* Disable the RNG. */
               reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR);
               bus_space_write_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR,
                   reg8 & ~I82802_RNG_HSR_ENABLE);
               bus_space_unmap(sc->sc_st, sc->sc_sh, I82802AC_WINSIZE);
               aprint_error_dev(sc->sc_dev,
                   "returns constant 0xff stream, RNG disabled.\n");
               return;
       }

       /*
        * Should test entropy source to ensure
        * that it passes the Statistical Random
        * Number Generator Tests in section 4.11.1,
        * FIPS PUB 140-1.
        *
        *      http://csrc.nist.gov/fips/fips1401.htm
        */

       aprint_debug_dev(sc->sc_dev, "random number generator enabled\n");

       callout_init(&sc->sc_rnd_ch, 0);
       /* FWH is polled for entropy, so no estimate is available. */
       rnd_attach_source(&sc->sc_rnd_source, device_xname(sc->sc_dev),
           RND_TYPE_RNG, RND_FLAG_COLLECT_VALUE);
       sc->sc_rnd_i = sizeof(sc->sc_rnd_ax);
       fwhrng_callout(sc);

       return;
}

static int
fwhrng_detach(device_t self, int flags)
{
       struct fwhrng_softc *sc;
       uint8_t reg8;

       sc = device_private(self);

       rnd_detach_source(&sc->sc_rnd_source);

       callout_halt(&sc->sc_rnd_ch, NULL);
       callout_destroy(&sc->sc_rnd_ch);

       /* Disable the RNG. */
       reg8 = bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR);
       bus_space_write_1(sc->sc_st, sc->sc_sh, I82802_RNG_HSR,
           reg8 & ~I82802_RNG_HSR_ENABLE);

       bus_space_unmap(sc->sc_st, sc->sc_sh, I82802AC_WINSIZE);

       return 0;
}

static void
fwhrng_callout(void *v)
{
       struct fwhrng_softc *sc = v;

       if ((bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_DSR) &
            I82802_RNG_DSR_VALID) != 0) {
               sc->sc_rnd_ax = (sc->sc_rnd_ax << NBBY) |
                   bus_space_read_1(sc->sc_st, sc->sc_sh, I82802_RNG_DR);
               if (--sc->sc_rnd_i == 0) {
                       sc->sc_rnd_i = sizeof(sc->sc_rnd_ax);
                       rnd_add_data(&sc->sc_rnd_source, &sc->sc_rnd_ax,
                           sizeof(sc->sc_rnd_ax),
                           sizeof(sc->sc_rnd_ax) * NBBY);
               }
       }
       callout_reset(&sc->sc_rnd_ch, 1, fwhrng_callout, sc);
}

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