// SPDX-License-Identifier: GPL-2.0+
/*
 *  ipmi_bt_sm.c
 *
 *  The state machine for an Open IPMI BT sub-driver under ipmi_si.c, part
 *  of the driver architecture at http://sourceforge.net/projects/openipmi 
 *
 *  Author:     Rocky Craig <first.last@hp.com>
 */

#define DEBUG /* So dev_dbg() is always available. */

#include <linux/kernel.h> /* For printk. */
#include <linux/string.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ipmi_msgdefs.h>         /* for completion codes */
#include "ipmi_si_sm.h"

#define BT_DEBUG_OFF    0       /* Used in production */
#define BT_DEBUG_ENABLE 1       /* Generic messages */
#define BT_DEBUG_MSG    2       /* Prints all request/response buffers */
#define BT_DEBUG_STATES 4       /* Verbose look at state changes */
/*
 * BT_DEBUG_OFF must be zero to correspond to the default uninitialized
 * value
 */

static int bt_debug; /* 0 == BT_DEBUG_OFF */

module_param(bt_debug, int, 0644);
MODULE_PARM_DESC(bt_debug, "debug bitmask, 1=enable, 2=messages, 4=states");

/*
 * Typical "Get BT Capabilities" values are 2-3 retries, 5-10 seconds,
 * and 64 byte buffers.  However, one HP implementation wants 255 bytes of
 * buffer (with a documented message of 160 bytes) so go for the max.
 * Since the Open IPMI architecture is single-message oriented at this
 * stage, the queue depth of BT is of no concern.
 */

#define BT_NORMAL_TIMEOUT       5       /* seconds */
#define BT_NORMAL_RETRY_LIMIT   2
#define BT_RESET_DELAY          6       /* seconds after warm reset */

/*
 * States are written in chronological order and usually cover
 * multiple rows of the state table discussion in the IPMI spec.
 */

enum bt_states {
        BT_STATE_IDLE = 0,      /* Order is critical in this list */
        BT_STATE_XACTION_START,
        BT_STATE_WRITE_BYTES,
        BT_STATE_WRITE_CONSUME,
        BT_STATE_READ_WAIT,
        BT_STATE_CLEAR_B2H,
        BT_STATE_READ_BYTES,
        BT_STATE_RESET1,        /* These must come last */
        BT_STATE_RESET2,
        BT_STATE_RESET3,
        BT_STATE_RESTART,
        BT_STATE_PRINTME,
        BT_STATE_LONG_BUSY      /* BT doesn't get hosed :-) */
};

/*
 * Macros seen at the end of state "case" blocks.  They help with legibility
 * and debugging.
 */

#define BT_STATE_CHANGE(X, Y) { bt->state = X; return Y; }

#define BT_SI_SM_RETURN(Y)   { last_printed = BT_STATE_PRINTME; return Y; }

struct si_sm_data {
        enum bt_states  state;
        unsigned char   seq;            /* BT sequence number */
        struct si_sm_io *io;
        unsigned char   write_data[IPMI_MAX_MSG_LENGTH + 2]; /* +2 for memcpy */
        int             write_count;
        unsigned char   read_data[IPMI_MAX_MSG_LENGTH + 2]; /* +2 for memcpy */
        int             read_count;
        int             truncated;
        long            timeout;        /* microseconds countdown */
        int             error_retries;  /* end of "common" fields */
        int             nonzero_status; /* hung BMCs stay all 0 */
        enum bt_states  complete;       /* to divert the state machine */
        long            BT_CAP_req2rsp;
        int             BT_CAP_retries; /* Recommended retries */
};

#define BT_CLR_WR_PTR   0x01    /* See IPMI 1.5 table 11.6.4 */
#define BT_CLR_RD_PTR   0x02
#define BT_H2B_ATN      0x04
#define BT_B2H_ATN      0x08
#define BT_SMS_ATN      0x10
#define BT_OEM0         0x20
#define BT_H_BUSY       0x40
#define BT_B_BUSY       0x80

/*
 * Some bits are toggled on each write: write once to set it, once
 * more to clear it; writing a zero does nothing.  To absolutely
 * clear it, check its state and write if set.  This avoids the "get
 * current then use as mask" scheme to modify one bit.  Note that the
 * variable "bt" is hardcoded into these macros.
 */

#define BT_STATUS       bt->io->inputb(bt->io, 0)
#define BT_CONTROL(x)   bt->io->outputb(bt->io, 0, x)

#define BMC2HOST        bt->io->inputb(bt->io, 1)
#define HOST2BMC(x)     bt->io->outputb(bt->io, 1, x)

#define BT_INTMASK_R    bt->io->inputb(bt->io, 2)
#define BT_INTMASK_W(x) bt->io->outputb(bt->io, 2, x)

/*
 * Convenience routines for debugging.  These are not multi-open safe!
 * Note the macros have hardcoded variables in them.
 */

static char *state2txt(unsigned char state)
{
        switch (state) {
        case BT_STATE_IDLE:             return("IDLE");
        case BT_STATE_XACTION_START:    return("XACTION");
        case BT_STATE_WRITE_BYTES:      return("WR_BYTES");
        case BT_STATE_WRITE_CONSUME:    return("WR_CONSUME");
        case BT_STATE_READ_WAIT:        return("RD_WAIT");
        case BT_STATE_CLEAR_B2H:        return("CLEAR_B2H");
        case BT_STATE_READ_BYTES:       return("RD_BYTES");
        case BT_STATE_RESET1:           return("RESET1");
        case BT_STATE_RESET2:           return("RESET2");
        case BT_STATE_RESET3:           return("RESET3");
        case BT_STATE_RESTART:          return("RESTART");
        case BT_STATE_LONG_BUSY:        return("LONG_BUSY");
        }
        return("BAD STATE");
}
#define STATE2TXT state2txt(bt->state)

static char *status2txt(unsigned char status)
{
        /*
         * This cannot be called by two threads at the same time and
         * the buffer is always consumed immediately, so the static is
         * safe to use.
         */
        static char buf[40];

        strcpy(buf, "[ ");
        if (status & BT_B_BUSY)
                strcat(buf, "B_BUSY ");
        if (status & BT_H_BUSY)
                strcat(buf, "H_BUSY ");
        if (status & BT_OEM0)
                strcat(buf, "OEM0 ");
        if (status & BT_SMS_ATN)
                strcat(buf, "SMS ");
        if (status & BT_B2H_ATN)
                strcat(buf, "B2H ");
        if (status & BT_H2B_ATN)
                strcat(buf, "H2B ");
        strcat(buf, "]");
        return buf;
}
#define STATUS2TXT status2txt(status)

/* called externally at insmod time, and internally on cleanup */

static unsigned int bt_init_data(struct si_sm_data *bt, struct si_sm_io *io)
{
        memset(bt, 0, sizeof(struct si_sm_data));
        if (bt->io != io) {
                /* external: one-time only things */
                bt->io = io;
                bt->seq = 0;
        }
        bt->state = BT_STATE_IDLE;      /* start here */
        bt->complete = BT_STATE_IDLE;   /* end here */
        bt->BT_CAP_req2rsp = BT_NORMAL_TIMEOUT * USEC_PER_SEC;
        bt->BT_CAP_retries = BT_NORMAL_RETRY_LIMIT;
        return 3; /* We claim 3 bytes of space; ought to check SPMI table */
}

/* Jam a completion code (probably an error) into a response */

static void force_result(struct si_sm_data *bt, unsigned char completion_code)
{
        bt->read_data[0] = 4;                           /* # following bytes */
        bt->read_data[1] = bt->write_data[1] | 4;       /* Odd NetFn/LUN */
        bt->read_data[2] = bt->write_data[2];           /* seq (ignored) */
        bt->read_data[3] = bt->write_data[3];           /* Command */
        bt->read_data[4] = completion_code;
        bt->read_count = 5;
}

/* The upper state machine starts here */

static int bt_start_transaction(struct si_sm_data *bt,
                                unsigned char *data,
                                unsigned int size)
{
        unsigned int i;

        if (size < 2)
                return IPMI_REQ_LEN_INVALID_ERR;
        if (size > IPMI_MAX_MSG_LENGTH)
                return IPMI_REQ_LEN_EXCEEDED_ERR;

        if (bt->state == BT_STATE_LONG_BUSY)
                return IPMI_NODE_BUSY_ERR;

        if (bt->state != BT_STATE_IDLE) {
                dev_warn(bt->io->dev, "BT in invalid state %d\n", bt->state);
                return IPMI_NOT_IN_MY_STATE_ERR;
        }

        if (bt_debug & BT_DEBUG_MSG) {
                dev_dbg(bt->io->dev, "+++++++++++++++++ New command\n");
                dev_dbg(bt->io->dev, "NetFn/LUN CMD [%d data]:", size - 2);
                for (i = 0; i < size; i ++)
                        pr_cont(" %02x", data[i]);
                pr_cont("\n");
        }
        bt->write_data[0] = size + 1;   /* all data plus seq byte */
        bt->write_data[1] = *data;      /* NetFn/LUN */
        bt->write_data[2] = bt->seq++;
        memcpy(bt->write_data + 3, data + 1, size - 1);
        bt->write_count = size + 2;
        bt->error_retries = 0;
        bt->nonzero_status = 0;
        bt->truncated = 0;
        bt->state = BT_STATE_XACTION_START;
        bt->timeout = bt->BT_CAP_req2rsp;
        force_result(bt, IPMI_ERR_UNSPECIFIED);
        return 0;
}

/*
 * After the upper state machine has been told SI_SM_TRANSACTION_COMPLETE
 * it calls this.  Strip out the length and seq bytes.
 */

static int bt_get_result(struct si_sm_data *bt,
                         unsigned char *data,
                         unsigned int length)
{
        int i, msg_len;

        msg_len = bt->read_count - 2;           /* account for length & seq */
        if (msg_len < 3 || msg_len > IPMI_MAX_MSG_LENGTH) {
                force_result(bt, IPMI_ERR_UNSPECIFIED);
                msg_len = 3;
        }
        data[0] = bt->read_data[1];
        data[1] = bt->read_data[3];
        if (length < msg_len || bt->truncated) {
                data[2] = IPMI_ERR_MSG_TRUNCATED;
                msg_len = 3;
        } else
                memcpy(data + 2, bt->read_data + 4, msg_len - 2);

        if (bt_debug & BT_DEBUG_MSG) {
                dev_dbg(bt->io->dev, "result %d bytes:", msg_len);
                for (i = 0; i < msg_len; i++)
                        pr_cont(" %02x", data[i]);
                pr_cont("\n");
        }
        return msg_len;
}

/* This bit's functionality is optional */
#define BT_BMC_HWRST    0x80

static void reset_flags(struct si_sm_data *bt)
{
        if (bt_debug)
                dev_dbg(bt->io->dev, "flag reset %s\n", status2txt(BT_STATUS));
        if (BT_STATUS & BT_H_BUSY)
                BT_CONTROL(BT_H_BUSY);  /* force clear */
        BT_CONTROL(BT_CLR_WR_PTR);      /* always reset */
        BT_CONTROL(BT_SMS_ATN);         /* always clear */
        BT_INTMASK_W(BT_BMC_HWRST);
}

/*
 * Get rid of an unwanted/stale response.  This should only be needed for
 * BMCs that support multiple outstanding requests.
 */

static void drain_BMC2HOST(struct si_sm_data *bt)
{
        int i, size;

        if (!(BT_STATUS & BT_B2H_ATN))  /* Not signalling a response */
                return;

        BT_CONTROL(BT_H_BUSY);          /* now set */
        BT_CONTROL(BT_B2H_ATN);         /* always clear */
        BT_STATUS;                      /* pause */
        BT_CONTROL(BT_B2H_ATN);         /* some BMCs are stubborn */
        BT_CONTROL(BT_CLR_RD_PTR);      /* always reset */
        if (bt_debug)
                dev_dbg(bt->io->dev, "stale response %s; ",
                        status2txt(BT_STATUS));
        size = BMC2HOST;
        for (i = 0; i < size ; i++)
                BMC2HOST;
        BT_CONTROL(BT_H_BUSY);          /* now clear */
        if (bt_debug)
                pr_cont("drained %d bytes\n", size + 1);
}

static inline void write_all_bytes(struct si_sm_data *bt)
{
        int i;

        if (bt_debug & BT_DEBUG_MSG) {
                dev_dbg(bt->io->dev, "write %d bytes seq=0x%02X",
                        bt->write_count, bt->seq);
                for (i = 0; i < bt->write_count; i++)
                        pr_cont(" %02x", bt->write_data[i]);
                pr_cont("\n");
        }
        for (i = 0; i < bt->write_count; i++)
                HOST2BMC(bt->write_data[i]);
}

static inline int read_all_bytes(struct si_sm_data *bt)
{
        unsigned int i;

        /*
         * length is "framing info", minimum = 4: NetFn, Seq, Cmd, cCode.
         * Keep layout of first four bytes aligned with write_data[]
         */

        bt->read_data[0] = BMC2HOST;
        bt->read_count = bt->read_data[0];

        if (bt->read_count < 4 || bt->read_count >= IPMI_MAX_MSG_LENGTH) {
                if (bt_debug & BT_DEBUG_MSG)
                        dev_dbg(bt->io->dev,
                                "bad raw rsp len=%d\n", bt->read_count);
                bt->truncated = 1;
                return 1;       /* let next XACTION START clean it up */
        }
        for (i = 1; i <= bt->read_count; i++)
                bt->read_data[i] = BMC2HOST;
        bt->read_count++;       /* Account internally for length byte */

        if (bt_debug & BT_DEBUG_MSG) {
                int max = bt->read_count;

                dev_dbg(bt->io->dev,
                        "got %d bytes seq=0x%02X", max, bt->read_data[2]);
                if (max > 16)
                        max = 16;
                for (i = 0; i < max; i++)
                        pr_cont(" %02x", bt->read_data[i]);
                pr_cont("%s\n", bt->read_count == max ? "" : " ...");
        }

        /* per the spec, the (NetFn[1], Seq[2], Cmd[3]) tuples must match */
        if ((bt->read_data[3] == bt->write_data[3]) &&
            (bt->read_data[2] == bt->write_data[2]) &&
            ((bt->read_data[1] & 0xF8) == (bt->write_data[1] & 0xF8)))
                        return 1;

        if (bt_debug & BT_DEBUG_MSG)
                dev_dbg(bt->io->dev,
                        "IPMI BT: bad packet: want 0x(%02X, %02X, %02X) got (%02X, %02X, %02X)\n",
                        bt->write_data[1] | 0x04, bt->write_data[2],
                        bt->write_data[3],
                        bt->read_data[1],  bt->read_data[2],  bt->read_data[3]);
        return 0;
}

/* Restart if retries are left, or return an error completion code */

static enum si_sm_result error_recovery(struct si_sm_data *bt,
                                        unsigned char status,
                                        unsigned char cCode)
{
        char *reason;

        bt->timeout = bt->BT_CAP_req2rsp;

        switch (cCode) {
        case IPMI_TIMEOUT_ERR:
                reason = "timeout";
                break;
        default:
                reason = "internal error";
                break;
        }

        dev_warn(bt->io->dev, "IPMI BT: %s in %s %s ", /* open-ended line */
                 reason, STATE2TXT, STATUS2TXT);

        /*
         * Per the IPMI spec, retries are based on the sequence number
         * known only to this module, so manage a restart here.
         */
        (bt->error_retries)++;
        if (bt->error_retries < bt->BT_CAP_retries) {
                pr_cont("%d retries left\n",
                        bt->BT_CAP_retries - bt->error_retries);
                bt->state = BT_STATE_RESTART;
                return SI_SM_CALL_WITHOUT_DELAY;
        }

        dev_warn(bt->io->dev, "failed %d retries, sending error response\n",
                 bt->BT_CAP_retries);
        if (!bt->nonzero_status)
                dev_err(bt->io->dev, "stuck, try power cycle\n");

        /* this is most likely during insmod */
        else if (bt->seq <= (unsigned char)(bt->BT_CAP_retries & 0xFF)) {
                dev_warn(bt->io->dev, "BT reset (takes 5 secs)\n");
                bt->state = BT_STATE_RESET1;
                return SI_SM_CALL_WITHOUT_DELAY;
        }

        /*
         * Concoct a useful error message, set up the next state, and
         * be done with this sequence.
         */

        bt->state = BT_STATE_IDLE;
        switch (cCode) {
        case IPMI_TIMEOUT_ERR:
                if (status & BT_B_BUSY) {
                        cCode = IPMI_NODE_BUSY_ERR;
                        bt->state = BT_STATE_LONG_BUSY;
                }
                break;
        default:
                break;
        }
        force_result(bt, cCode);
        return SI_SM_TRANSACTION_COMPLETE;
}

/* Check status and (usually) take action and change this state machine. */

static enum si_sm_result bt_event(struct si_sm_data *bt, long time)
{
        unsigned char status;
        static enum bt_states last_printed = BT_STATE_PRINTME;
        int i;

        status = BT_STATUS;
        bt->nonzero_status |= status;
        if ((bt_debug & BT_DEBUG_STATES) && (bt->state != last_printed)) {
                dev_dbg(bt->io->dev, "BT: %s %s TO=%ld - %ld\n",
                        STATE2TXT,
                        STATUS2TXT,
                        bt->timeout,
                        time);
                last_printed = bt->state;
        }

        /*
         * Commands that time out may still (eventually) provide a response.
         * This stale response will get in the way of a new response so remove
         * it if possible (hopefully during IDLE).  Even if it comes up later
         * it will be rejected by its (now-forgotten) seq number.
         */

        if ((bt->state < BT_STATE_WRITE_BYTES) && (status & BT_B2H_ATN)) {
                drain_BMC2HOST(bt);
                BT_SI_SM_RETURN(SI_SM_CALL_WITH_DELAY);
        }

        if ((bt->state != BT_STATE_IDLE) &&
            (bt->state <  BT_STATE_PRINTME)) {
                /* check timeout */
                bt->timeout -= time;
                if ((bt->timeout < 0) && (bt->state < BT_STATE_RESET1))
                        return error_recovery(bt,
                                              status,
                                              IPMI_TIMEOUT_ERR);
        }

        switch (bt->state) {

        /*
         * Idle state first checks for asynchronous messages from another
         * channel, then does some opportunistic housekeeping.
         */

        case BT_STATE_IDLE:
                if (status & BT_SMS_ATN) {
                        BT_CONTROL(BT_SMS_ATN); /* clear it */
                        return SI_SM_ATTN;
                }

                if (status & BT_H_BUSY)         /* clear a leftover H_BUSY */
                        BT_CONTROL(BT_H_BUSY);

                BT_SI_SM_RETURN(SI_SM_IDLE);

        case BT_STATE_XACTION_START:
                if (status & (BT_B_BUSY | BT_H2B_ATN))
                        BT_SI_SM_RETURN(SI_SM_CALL_WITH_DELAY);
                if (BT_STATUS & BT_H_BUSY)
                        BT_CONTROL(BT_H_BUSY);  /* force clear */
                BT_STATE_CHANGE(BT_STATE_WRITE_BYTES,
                                SI_SM_CALL_WITHOUT_DELAY);

        case BT_STATE_WRITE_BYTES:
                if (status & BT_H_BUSY)
                        BT_CONTROL(BT_H_BUSY);  /* clear */
                BT_CONTROL(BT_CLR_WR_PTR);
                write_all_bytes(bt);
                BT_CONTROL(BT_H2B_ATN); /* can clear too fast to catch */
                BT_STATE_CHANGE(BT_STATE_WRITE_CONSUME,
                                SI_SM_CALL_WITHOUT_DELAY);

        case BT_STATE_WRITE_CONSUME:
                if (status & (BT_B_BUSY | BT_H2B_ATN))
                        BT_SI_SM_RETURN(SI_SM_CALL_WITH_DELAY);
                BT_STATE_CHANGE(BT_STATE_READ_WAIT,
                                SI_SM_CALL_WITHOUT_DELAY);

        /* Spinning hard can suppress B2H_ATN and force a timeout */

        case BT_STATE_READ_WAIT:
                if (!(status & BT_B2H_ATN))
                        BT_SI_SM_RETURN(SI_SM_CALL_WITH_DELAY);
                BT_CONTROL(BT_H_BUSY);          /* set */

                /*
                 * Uncached, ordered writes should just proceed serially but
                 * some BMCs don't clear B2H_ATN with one hit.  Fast-path a
                 * workaround without too much penalty to the general case.
                 */

                BT_CONTROL(BT_B2H_ATN);         /* clear it to ACK the BMC */
                BT_STATE_CHANGE(BT_STATE_CLEAR_B2H,
                                SI_SM_CALL_WITHOUT_DELAY);

        case BT_STATE_CLEAR_B2H:
                if (status & BT_B2H_ATN) {
                        /* keep hitting it */
                        BT_CONTROL(BT_B2H_ATN);
                        BT_SI_SM_RETURN(SI_SM_CALL_WITH_DELAY);
                }
                BT_STATE_CHANGE(BT_STATE_READ_BYTES,
                                SI_SM_CALL_WITHOUT_DELAY);

        case BT_STATE_READ_BYTES:
                if (!(status & BT_H_BUSY))
                        /* check in case of retry */
                        BT_CONTROL(BT_H_BUSY);
                BT_CONTROL(BT_CLR_RD_PTR);      /* start of BMC2HOST buffer */
                i = read_all_bytes(bt);         /* true == packet seq match */
                BT_CONTROL(BT_H_BUSY);          /* NOW clear */
                if (!i)                         /* Not my message */
                        BT_STATE_CHANGE(BT_STATE_READ_WAIT,
                                        SI_SM_CALL_WITHOUT_DELAY);
                bt->state = bt->complete;
                return bt->state == BT_STATE_IDLE ?     /* where to next? */
                        SI_SM_TRANSACTION_COMPLETE :    /* normal */
                        SI_SM_CALL_WITHOUT_DELAY;       /* Startup magic */

        case BT_STATE_LONG_BUSY:        /* For example: after FW update */
                if (!(status & BT_B_BUSY)) {
                        reset_flags(bt);        /* next state is now IDLE */
                        bt_init_data(bt, bt->io);
                }
                return SI_SM_CALL_WITH_DELAY;   /* No repeat printing */

        case BT_STATE_RESET1:
                reset_flags(bt);
                drain_BMC2HOST(bt);
                BT_STATE_CHANGE(BT_STATE_RESET2,
                                SI_SM_CALL_WITH_DELAY);

        case BT_STATE_RESET2:           /* Send a soft reset */
                BT_CONTROL(BT_CLR_WR_PTR);
                HOST2BMC(3);            /* number of bytes following */
                HOST2BMC(0x18);         /* NetFn/LUN == Application, LUN 0 */
                HOST2BMC(42);           /* Sequence number */
                HOST2BMC(3);            /* Cmd == Soft reset */
                BT_CONTROL(BT_H2B_ATN);
                bt->timeout = BT_RESET_DELAY * USEC_PER_SEC;
                BT_STATE_CHANGE(BT_STATE_RESET3,
                                SI_SM_CALL_WITH_DELAY);

        case BT_STATE_RESET3:           /* Hold off everything for a bit */
                if (bt->timeout > 0)
                        return SI_SM_CALL_WITH_DELAY;
                drain_BMC2HOST(bt);
                BT_STATE_CHANGE(BT_STATE_RESTART,
                                SI_SM_CALL_WITH_DELAY);

        case BT_STATE_RESTART:          /* don't reset retries or seq! */
                bt->read_count = 0;
                bt->nonzero_status = 0;
                bt->timeout = bt->BT_CAP_req2rsp;
                BT_STATE_CHANGE(BT_STATE_XACTION_START,
                                SI_SM_CALL_WITH_DELAY);

        default:        /* should never occur */
                return error_recovery(bt,
                                      status,
                                      IPMI_ERR_UNSPECIFIED);
        }
        return SI_SM_CALL_WITH_DELAY;
}

static int bt_detect(struct si_sm_data *bt)
{
        unsigned char GetBT_CAP[] = { 0x18, 0x36 };
        unsigned char BT_CAP[8];
        enum si_sm_result smi_result;
        int rv;

        /*
         * It's impossible for the BT status and interrupt registers to be
         * all 1's, (assuming a properly functioning, self-initialized BMC)
         * but that's what you get from reading a bogus address, so we
         * test that first.  The calling routine uses negative logic.
         */

        if ((BT_STATUS == 0xFF) && (BT_INTMASK_R == 0xFF))
                return 1;
        reset_flags(bt);

        /*
         * Try getting the BT capabilities here.
         */
        rv = bt_start_transaction(bt, GetBT_CAP, sizeof(GetBT_CAP));
        if (rv) {
                dev_warn(bt->io->dev,
                         "Can't start capabilities transaction: %d\n", rv);
                goto out_no_bt_cap;
        }

        smi_result = SI_SM_CALL_WITHOUT_DELAY;
        for (;;) {
                if (smi_result == SI_SM_CALL_WITH_DELAY ||
                    smi_result == SI_SM_CALL_WITH_TICK_DELAY) {
                        schedule_timeout_uninterruptible(1);
                        smi_result = bt_event(bt, jiffies_to_usecs(1));
                } else if (smi_result == SI_SM_CALL_WITHOUT_DELAY) {
                        smi_result = bt_event(bt, 0);
                } else
                        break;
        }

        rv = bt_get_result(bt, BT_CAP, sizeof(BT_CAP));
        bt_init_data(bt, bt->io);
        if (rv < 8) {
                dev_warn(bt->io->dev, "bt cap response too short: %d\n", rv);
                goto out_no_bt_cap;
        }

        if (BT_CAP[2]) {
                dev_warn(bt->io->dev, "Error fetching bt cap: %x\n", BT_CAP[2]);
out_no_bt_cap:
                dev_warn(bt->io->dev, "using default values\n");
        } else {
                bt->BT_CAP_req2rsp = BT_CAP[6] * USEC_PER_SEC;
                bt->BT_CAP_retries = BT_CAP[7];
        }

        dev_info(bt->io->dev, "req2rsp=%ld secs retries=%d\n",
                 bt->BT_CAP_req2rsp / USEC_PER_SEC, bt->BT_CAP_retries);

        return 0;
}

static void bt_cleanup(struct si_sm_data *bt)
{
}

static int bt_size(void)
{
        return sizeof(struct si_sm_data);
}

const struct si_sm_handlers bt_smi_handlers = {
        .init_data              = bt_init_data,
        .start_transaction      = bt_start_transaction,
        .get_result             = bt_get_result,
        .event                  = bt_event,
        .detect                 = bt_detect,
        .cleanup                = bt_cleanup,
        .size                   = bt_size,
};