/*      $NetBSD: scmd.c,v 1.3 2022/10/06 19:38:54 andvar Exp $  */

/*
* Copyright (c) 2021 Brad Spencer <[email protected]>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: scmd.c,v 1.3 2022/10/06 19:38:54 andvar Exp $");

/*
* Common driver for the Sparkfun Serial motor controller.
* Calls out to specific frontends to move bits.
*/

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/device.h>
#include <sys/module.h>
#include <sys/conf.h>
#include <sys/sysctl.h>
#include <sys/mutex.h>
#include <sys/pool.h>
#include <sys/kmem.h>

#include <dev/i2c/i2cvar.h>
#include <dev/spi/spivar.h>
#include <dev/ic/scmdreg.h>
#include <dev/ic/scmdvar.h>

void            scmd_attach(struct scmd_sc *);
static void     scmd_wait_restart(struct scmd_sc *, bool);
static int      scmd_get_topaddr(struct scmd_sc *);
static int      scmd_verify_sysctl(SYSCTLFN_ARGS);
static int      scmd_local_read(struct scmd_sc *, uint8_t, uint8_t *);
static int      scmd_remote_read(struct scmd_sc *, int, uint8_t *);
static int      scmd_local_write(struct scmd_sc *, uint8_t, uint8_t);
static int      scmd_remote_write(struct scmd_sc *, int, uint8_t);

#define SCMD_DEBUG
#ifdef SCMD_DEBUG
#define DPRINTF(s, l, x) \
   do { \
       if (l <= s->sc_scmddebug) \
           printf x; \
   } while (/*CONSTCOND*/0)
#else
#define DPRINTF(s, l, x)
#endif

extern struct cfdriver scmd_cd;

static dev_type_open(scmd_open);
static dev_type_read(scmd_read);
static dev_type_write(scmd_write);
static dev_type_close(scmd_close);
const struct cdevsw scmd_cdevsw = {
       .d_open = scmd_open,
       .d_close = scmd_close,
       .d_read = scmd_read,
       .d_write = scmd_write,
       .d_ioctl = noioctl,
       .d_stop = nostop,
       .d_tty = notty,
       .d_poll = nopoll,
       .d_mmap = nommap,
       .d_kqfilter = nokqfilter,
       .d_discard = nodiscard,
       .d_flag = D_OTHER
};

static int
scmd_verify_sysctl(SYSCTLFN_ARGS)
{
       int error, t;
       struct sysctlnode node;

       node = *rnode;
       t = *(int *)rnode->sysctl_data;
       node.sysctl_data = &t;
       error = sysctl_lookup(SYSCTLFN_CALL(&node));
       if (error || newp == NULL)
               return error;

       if (t < 0)
               return EINVAL;

       *(int *)rnode->sysctl_data = t;

       return 0;
}

static int
scmd_sysctl_init(struct scmd_sc *sc)
{
       int error;
       const struct sysctlnode *cnode;
       int sysctlroot_num;

       if ((error = sysctl_createv(&sc->sc_scmdlog, 0, NULL, &cnode,
           0, CTLTYPE_NODE, device_xname(sc->sc_dev),
           SYSCTL_DESCR("scmd controls"), NULL, 0, NULL, 0, CTL_HW,
           CTL_CREATE, CTL_EOL)) != 0)
               return error;

       sysctlroot_num = cnode->sysctl_num;

#ifdef SCMD_DEBUG
       if ((error = sysctl_createv(&sc->sc_scmdlog, 0, NULL, &cnode,
           CTLFLAG_READWRITE, CTLTYPE_INT, "debug",
           SYSCTL_DESCR("Debug level"), scmd_verify_sysctl, 0,
           &sc->sc_scmddebug, 0, CTL_HW, sysctlroot_num, CTL_CREATE,
           CTL_EOL)) != 0)
               return error;

#endif

       return 0;
}

/* Restarts and re-enumeration of the device is a little strange.
* It will take a very long time to complete.  It would be more polite
* to use a condvar for this wait, but it was noticed that those may
* not work if done too early in boot and will just hang the boot, so
* delay is also offered as an option.
*/
static void
scmd_wait_restart(struct scmd_sc *sc, bool usedelay)
{
       int error;
       uint8_t buf = SCMD_HOLE_VALUE;
       int c = 0;

       do {
               if (usedelay) {
                       delay(1000000);
               } else {
                       mutex_enter(&sc->sc_condmutex);
                       cv_timedwait(&sc->sc_condvar, &sc->sc_condmutex,
                           mstohz(1000));
                       mutex_exit(&sc->sc_condmutex);
               }

               error = (*(sc->sc_func_read_register))(sc, SCMD_REG_STATUS_1, &buf);

               DPRINTF(sc, 2, ("%s: Read back status after restart: %02x %d\n",
                   device_xname(sc->sc_dev), buf, error));

               c++;
       } while (c <= 20 && buf != 0x00);
}

static int
scmd_get_topaddr(struct scmd_sc *sc)
{
       uint8_t topaddr;
       int error;

       error = (*(sc->sc_func_read_register))(sc, SCMD_REG_SLV_TOP_ADDR, &topaddr);

       if (error) {
               topaddr = 0;
       }
       return topaddr;
}

/* Note that this assumes that you can actually access the device.
* In at least one case right now, SPI on a Raspberry PI 3, the pins
* have not been set up to allow SPI to function, but nothing is
* returned as an error either.  We do the best that can be done right
* now.
*/
void
scmd_attach(struct scmd_sc *sc)
{
       int error;

       aprint_normal("\n");

       if ((error = scmd_sysctl_init(sc)) != 0) {
               aprint_error_dev(sc->sc_dev, "Can't setup sysctl tree (%d)\n", error);
               goto out;
       }

       error = (*(sc->sc_func_acquire_bus))(sc);
       if (error) {
               aprint_error_dev(sc->sc_dev, "Could not acquire iic bus: %d\n",
                   error);
               goto out;
       }

       error = (*(sc->sc_func_write_register))(sc, SCMD_REG_CONTROL_1, SCMD_CONTROL_1_RESTART);
       if (error != 0)
               aprint_error_dev(sc->sc_dev, "Reset failed: %d\n", error);

       scmd_wait_restart(sc, true);

       sc->sc_topaddr = scmd_get_topaddr(sc);

       DPRINTF(sc, 2, ("%s: Top remote module address: %02x\n",
           device_xname(sc->sc_dev), sc->sc_topaddr));

       uint8_t fwversion;
       uint8_t id;
       uint8_t pins;

       error = (*(sc->sc_func_read_register))(sc, SCMD_REG_FID, &fwversion);
       if (error) {
               aprint_error_dev(sc->sc_dev, "Read of FID failed: %d\n",
                   error);
               goto out;
       }

       error = (*(sc->sc_func_read_register))(sc, SCMD_REG_ID, &id);
       if (error) {
               aprint_error_dev(sc->sc_dev, "Read of ID failed: %d\n",
                   error);
               goto out;
       }

       error = (*(sc->sc_func_read_register))(sc, SCMD_REG_CONFIG_BITS, &pins);
       if (error) {
               aprint_error_dev(sc->sc_dev, "Read of CONFIG_BITS failed: %d\n",
                   error);
               goto out;
       }

       aprint_normal_dev(sc->sc_dev, "Sparkfun Serial motor controller, "
           "Firmware version: %02x, ID: %02x%s, Jumper pins: %02x\n",
           fwversion, id, (id == SCMD_EXPECTED_ID) ? " (expected ID)" : " (unexpected ID)",
           pins);

out:
       (*(sc->sc_func_release_bus))(sc);
       if (error != 0) {
               aprint_error_dev(sc->sc_dev, "Unable to setup device\n");
       }

       return;
}

/* This device has the effect of creating a virtual register space of all
* of the attached modules.  All you have to do is read and write to anything
* in that space and you can hit the main module and all chained slave modules
* without having to worry about the view port set up.
*
* 0x00 - 0x7E -- the first and main module
* 0x7F - 0xFD -- the first slaved module
* ...etc...
*
*/
static int
scmd_open(dev_t dev, int flags, int fmt, struct lwp *l)
{
       struct scmd_sc *sc;

       sc = device_lookup_private(&scmd_cd, minor(dev));
       if (!sc)
               return ENXIO;

       if (sc->sc_opened)
               return EBUSY;

       /* This is a meaningless assignment to keep GCC from
        * complaining.
        */
       sc->sc_func_attach = &scmd_attach;

       mutex_enter(&sc->sc_mutex);
       sc->sc_opened = true;
       mutex_exit(&sc->sc_mutex);

       return 0;
}

static int
scmd_maxregister(int topaddr)
{
       if (topaddr >= SCMD_REMOTE_ADDR_LOW &&
           topaddr <= SCMD_REMOTE_ADDR_HIGH) {
               int i = (topaddr - SCMD_REMOTE_ADDR_LOW) + 2;
               return (SCMD_REG_SIZE * i) - 1;
       } else {
               return SCMD_LAST_REG;
       }
}

/* Please note that that setting up and using the view port
* to get access to SCMD devices that are chained off of the main
* device is not atomic.  Hopefully this all happens fast enough
* so that nothing can sneak in and mess with the registers.
*/
static int
scmd_set_view_port(struct scmd_sc *sc, int reg)
{
       int err;
       int loc = reg / SCMD_REG_SIZE;
       uint8_t vpi2creg = reg % SCMD_REG_SIZE;
       uint8_t vpi2caddr = (SCMD_REMOTE_ADDR_LOW + loc) - 1;

       DPRINTF(sc, 2, ("%s: View port addr: %02x ; View port register: %02x ; Orig register: %04x\n",
           device_xname(sc->sc_dev), vpi2caddr, vpi2creg, reg));

       err = (*(sc->sc_func_write_register))(sc, SCMD_REG_REM_ADDR, vpi2caddr);
       if (! err)
               err = (*(sc->sc_func_write_register))(sc, SCMD_REG_REM_OFFSET, vpi2creg);

       return err;
}

/* It is not defined what happens if the Not Defined in the datasheet
* registers are accessed, so block them.
*/
static int
scmd_local_read(struct scmd_sc *sc, uint8_t reg, uint8_t *buf)
{
       if (SCMD_IS_HOLE(reg)) {
               *buf = SCMD_HOLE_VALUE;
               return 0;
       }

       return (*(sc->sc_func_read_register))(sc, reg, buf);
}

static int
scmd_remote_read(struct scmd_sc *sc, int reg, uint8_t *buf)
{
       int err;
       int c;
       uint8_t b;

       if (SCMD_IS_HOLE(reg % SCMD_REG_SIZE)) {
               *buf = SCMD_HOLE_VALUE;
               return 0;
       }

       err = scmd_set_view_port(sc, reg);
       if (! err) {
               b = 0xff; /* you can write anything here.. it doesn't matter */
               err = (*(sc->sc_func_write_register))(sc, SCMD_REG_REM_READ, b);
               if (! err) {
                       /* So ...  there is no way to really know that the data is ready and
                        * there is no way to know if there was an error in the master module reading
                        * the data from the slave module.  The data sheet says wait 5ms.. so do that
                        * and see if the register cleared, but don't wait forever...  I can't see how
                        * it would not be possible to read junk at times.
                        */
                       c = 0;
                       do {
                               delay(5000);
                               err = (*(sc->sc_func_read_register))(sc, SCMD_REG_REM_READ, &b);
                               c++;
                       } while ((c < 10) && (b != 0x00) && (!err));
                       /* We can only hope that whatever was read from the slave module is there */
                       if (! err)
                               err = (*(sc->sc_func_read_register))(sc, SCMD_REG_REM_DATA_RD, buf);
               }
       }

       return err;
}

static int
scmd_read(dev_t dev, struct uio *uio, int flags)
{
       struct scmd_sc *sc;
       int error;

       if ((sc = device_lookup_private(&scmd_cd, minor(dev))) == NULL)
               return ENXIO;

       /* We do not make this an error.  There is nothing wrong with running
        * off the end here, just return EOF.
        */
       if (uio->uio_offset > scmd_maxregister(sc->sc_topaddr))
               return 0;

       if ((error = (*(sc->sc_func_acquire_bus))(sc)) != 0)
               return error;

       while (uio->uio_resid &&
           uio->uio_offset <= scmd_maxregister(sc->sc_topaddr) &&
           !sc->sc_dying) {
               uint8_t buf;
               int reg_addr = uio->uio_offset;

               if (reg_addr <= SCMD_LAST_REG) {
                       if ((error = scmd_local_read(sc, (uint8_t)reg_addr, &buf)) != 0) {
                               (*(sc->sc_func_release_bus))(sc);
                               aprint_error_dev(sc->sc_dev,
                                   "%s: local read failed at 0x%02x: %d\n",
                                   __func__, reg_addr, error);
                               return error;
                       }
               } else {
                       if ((error = scmd_remote_read(sc, reg_addr, &buf)) != 0) {
                               (*(sc->sc_func_release_bus))(sc);
                               aprint_error_dev(sc->sc_dev,
                                   "%s: remote read failed at 0x%02x: %d\n",
                                   __func__, reg_addr, error);
                               return error;
                       }
               }

               if (sc->sc_dying)
                       break;

               if ((error = uiomove(&buf, 1, uio)) != 0) {
                       (*(sc->sc_func_release_bus))(sc);
                       return error;
               }
       }

       (*(sc->sc_func_release_bus))(sc);

       if (sc->sc_dying) {
               return EIO;
       }

       return 0;
}

/* Same thing about the undefined registers.  Don't actually allow
* writes as it is not clear what happens when you do that.
*/
static int
scmd_local_write(struct scmd_sc *sc, uint8_t reg, uint8_t buf)
{
       if (SCMD_IS_HOLE(reg))
               return 0;

       return (*(sc->sc_func_write_register))(sc, reg, buf);
}

static int
scmd_remote_write(struct scmd_sc *sc, int reg, uint8_t buf)
{
       int err;
       int c;
       uint8_t b;

       if (SCMD_IS_HOLE(reg % SCMD_REG_SIZE)) {
               return 0;
       }

       err = scmd_set_view_port(sc, reg);
       if (! err) {
               /* We just sort of send this write off and wait to see if the register
                * clears.  There really isn't any indication that the data made it to the
                * slave modules and there really are not any errors reported.
                */
               err = (*(sc->sc_func_write_register))(sc, SCMD_REG_REM_DATA_WR, buf);
               if (! err) {
                       b = 0xff; /* you can write anything here.. it doesn't matter */
                       err = (*(sc->sc_func_write_register))(sc, SCMD_REG_REM_WRITE, b);
                       if (! err) {
                               c = 0;
                               do {
                                       delay(5000);
                                       err = (*(sc->sc_func_read_register))(sc, SCMD_REG_REM_WRITE, &b);
                                       c++;
                               } while ((c < 10) && (b != 0x00) && (!err));
                       }
               }
       }

       return err;
}

static int
scmd_write(dev_t dev, struct uio *uio, int flags)
{
       struct scmd_sc *sc;
       int error;

       if ((sc = device_lookup_private(&scmd_cd, minor(dev))) == NULL)
               return ENXIO;

       /* Same thing as read, this is not considered an error */
       if (uio->uio_offset > scmd_maxregister(sc->sc_topaddr))
               return 0;

       if ((error = (*(sc->sc_func_acquire_bus))(sc)) != 0)
               return error;

       while (uio->uio_resid &&
           uio->uio_offset <= scmd_maxregister(sc->sc_topaddr) &&
           !sc->sc_dying) {
               uint8_t buf;
               int reg_addr = uio->uio_offset;

               if ((error = uiomove(&buf, 1, uio)) != 0)
                       break;

               if (sc->sc_dying)
                       break;

               if (reg_addr <= SCMD_LAST_REG) {
                       if ((error = scmd_local_write(sc, (uint8_t)reg_addr, buf)) != 0) {
                               (*(sc->sc_func_release_bus))(sc);
                               aprint_error_dev(sc->sc_dev,
                                   "%s: local write failed at 0x%02x: %d\n",
                                   __func__, reg_addr, error);
                               return error;
                       }

                       /* If this was a local command to the control register that
                        * can perform re-enumeration, then do the wait thing.
                        * It is not as important that this be done for remote module
                        * access as the only thing that you could really do there is
                        * a restart and not re-enumeration, which is really what the wait
                        * is all about.
                        */
                       if (reg_addr == SCMD_REG_CONTROL_1) {
                               scmd_wait_restart(sc, false);

                               sc->sc_topaddr = scmd_get_topaddr(sc);
                               aprint_normal_dev(sc->sc_dev, "Highest I2C address on expansion bus is: %02x\n",
                                   sc->sc_topaddr);
                       }
               } else {
                       if ((error = scmd_remote_write(sc, reg_addr, buf)) != 0) {
                               (*(sc->sc_func_release_bus))(sc);
                               aprint_error_dev(sc->sc_dev,
                                   "%s: remote write failed at 0x%02x: %d\n",
                                   __func__, reg_addr, error);
                               return error;
                       }
               }
       }

       (*(sc->sc_func_release_bus))(sc);

       if (sc->sc_dying) {
               return EIO;
       }

       return error;
}

static int
scmd_close(dev_t dev, int flags, int fmt, struct lwp *l)
{
       struct scmd_sc *sc;

       sc = device_lookup_private(&scmd_cd, minor(dev));

       if (sc->sc_dying) {
               DPRINTF(sc, 2, ("%s: Telling all we are almost dead\n",
                   device_xname(sc->sc_dev)));
               mutex_enter(&sc->sc_dying_mutex);
               cv_signal(&sc->sc_cond_dying);
               mutex_exit(&sc->sc_dying_mutex);
               return EIO;
       }

       mutex_enter(&sc->sc_mutex);
       sc->sc_opened = false;
       mutex_exit(&sc->sc_mutex);

       return(0);
}

MODULE(MODULE_CLASS_DRIVER, scmd, NULL);

#ifdef _MODULE
CFDRIVER_DECL(scmd, DV_DULL, NULL);
#include "ioconf.c"
#endif

static int
scmd_modcmd(modcmd_t cmd, void *opaque)
{
#ifdef _MODULE
       int error = 0;
       int bmaj = -1, cmaj = -1;
#endif

       switch (cmd) {
       case MODULE_CMD_INIT:
#ifdef _MODULE
               error = devsw_attach("scmd", NULL, &bmaj,
                   &scmd_cdevsw, &cmaj);
               if (error) {
                       aprint_error("%s: unable to attach devsw: %d\n",
                           scmd_cd.cd_name, error);
                       return error;
               }

               error = config_init_component(cfdriver_ioconf_scmd,
                   cfattach_ioconf_scmd, cfdata_ioconf_scmd);
               if (error) {
                       aprint_error("%s: unable to init component: %d\n",
                           scmd_cd.cd_name, error);
                       devsw_detach(NULL, &scmd_cdevsw);
               }
               return error;
#else
               return 0;
#endif
       case MODULE_CMD_FINI:
#ifdef _MODULE
               error = config_fini_component(cfdriver_ioconf_scmd,
                   cfattach_ioconf_scmd, cfdata_ioconf_scmd);
               devsw_detach(NULL, &scmd_cdevsw);

               return error;
#else
               return 0;
#endif
       default:
               return ENOTTY;
       }
}

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