drivers/char/ipmi/ipmi_bt_sm.c

/*
 *  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/project/openipmi
 *
 *  Author:	Rocky Craig <first.last@hp.com>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  option) any later version.
 *
 *  THIS SOFTWARE IS PROVIDED ``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 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.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  675 Mass Ave, Cambridge, MA 02139, USA.  */

#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 */

static int bt_debug = 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_CAPABILITIES_BEGIN,
	BT_STATE_CAPABILITIES_END,
	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];
	int		write_count;
	unsigned char	read_data[IPMI_MAX_MSG_LENGTH];
	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 */
	int		BT_CAP_outreqs;
	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");
	case BT_STATE_CAPABILITIES_BEGIN: return("CAP_BEGIN");
	case BT_STATE_CAPABILITIES_END:	return("CAP_END");
	}
	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 * 1000000;
	bt->BT_CAP_retries = BT_NORMAL_RETRY_LIMIT;
	/* BT_CAP_outreqs == zero is a flag to read BT Capabilities */
	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)
		return IPMI_NOT_IN_MY_STATE_ERR;

	if (bt_debug & BT_DEBUG_MSG) {
		printk(KERN_WARNING "BT: +++++++++++++++++ New command\n");
		printk(KERN_WARNING "BT: NetFn/LUN CMD [%d data]:", size - 2);
		for (i = 0; i < size; i ++)
			printk (" %02x", data[i]);
		printk("\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) {
		printk (KERN_WARNING "BT: result %d bytes:", msg_len);
		for (i = 0; i < msg_len; i++)
			printk(" %02x", data[i]);
		printk ("\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)
		printk(KERN_WARNING "IPMI BT: 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)
		printk(KERN_WARNING "IPMI BT: 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)
		printk("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) {
		printk(KERN_WARNING "BT: write %d bytes seq=0x%02X",
			bt->write_count, bt->seq);
		for (i = 0; i < bt->write_count; i++)
			printk (" %02x", bt->write_data[i]);
		printk ("\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 char 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)
			printk(KERN_WARNING "BT: 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;

		printk(KERN_WARNING "BT: got %d bytes seq=0x%02X",
			max, bt->read_data[2]);
		if (max > 16)
			max = 16;
		for (i = 0; i < max; i++)
			printk (" %02x", bt->read_data[i]);
		printk ("%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)
		printk(KERN_WARNING "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;
	}

	printk(KERN_WARNING "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) {
		printk("%d retries left\n",
			bt->BT_CAP_retries - bt->error_retries);
		bt->state = BT_STATE_RESTART;
		return SI_SM_CALL_WITHOUT_DELAY;
	}

	printk("failed %d retries, sending error response\n",
		bt->BT_CAP_retries);
	if (!bt->nonzero_status)
		printk(KERN_ERR "IPMI BT: stuck, try power cycle\n");

	/* this is most likely during insmod */
	else if (bt->seq <= (unsigned char)(bt->BT_CAP_retries & 0xFF)) {
		printk(KERN_WARNING "IPMI: 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, BT_CAP[8];
	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)) {
		printk(KERN_WARNING "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);

		/* Read BT capabilities if it hasn't been done yet */
		if (!bt->BT_CAP_outreqs)
			BT_STATE_CHANGE(BT_STATE_CAPABILITIES_BEGIN,
					SI_SM_CALL_WITHOUT_DELAY);
		bt->timeout = bt->BT_CAP_req2rsp;
		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 proceeed 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 * 1000000;
		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);

	/* Get BT Capabilities, using timing of upper level state machine.
	   Set outreqs to prevent infinite loop on timeout. */
	case BT_STATE_CAPABILITIES_BEGIN:
		bt->BT_CAP_outreqs = 1;
		{
			unsigned char GetBT_CAP[] = { 0x18, 0x36 };
			bt->state = BT_STATE_IDLE;
			bt_start_transaction(bt, GetBT_CAP, sizeof(GetBT_CAP));
		}
		bt->complete = BT_STATE_CAPABILITIES_END;
		BT_STATE_CHANGE(BT_STATE_XACTION_START,
				SI_SM_CALL_WITH_DELAY);

	case BT_STATE_CAPABILITIES_END:
		i = bt_get_result(bt, BT_CAP, sizeof(BT_CAP));
		bt_init_data(bt, bt->io);
		if ((i == 8) && !BT_CAP[2]) {
			bt->BT_CAP_outreqs = BT_CAP[3];
			bt->BT_CAP_req2rsp = BT_CAP[6] * 1000000;
			bt->BT_CAP_retries = BT_CAP[7];
		} else
			printk(KERN_WARNING "IPMI BT: using default values\n");
		if (!bt->BT_CAP_outreqs)
			bt->BT_CAP_outreqs = 1;
		printk(KERN_WARNING "IPMI BT: req2rsp=%ld secs retries=%d\n",
			bt->BT_CAP_req2rsp / 1000000L, bt->BT_CAP_retries);
		bt->timeout = bt->BT_CAP_req2rsp;
		return SI_SM_CALL_WITHOUT_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)
{
	/* 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);
	return 0;
}

static void bt_cleanup(struct si_sm_data *bt)
{
}

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

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,
};