drivers/char/ipmi/ipmi_kcs_sm.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * ipmi_kcs_sm.c
  *
  * State machine for handling IPMI KCS interfaces.
  *
  * Author: MontaVista Software, Inc.
  *         Corey Minyard <minyard@mvista.com>
  *         source@mvista.com
  *
  * Copyright 2002 MontaVista Software Inc.
  */

 /*
  * This state machine is taken from the state machine in the IPMI spec,
  * pretty much verbatim.  If you have questions about the states, see
  * that document.
  */

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

 /* kcs_debug is a bit-field
  *	KCS_DEBUG_ENABLE -	turned on for now
  *	KCS_DEBUG_MSG    -	commands and their responses
  *	KCS_DEBUG_STATES -	state machine
  */
 #define KCS_DEBUG_STATES	4
 #define KCS_DEBUG_MSG		2
 #define	KCS_DEBUG_ENABLE	1

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

 /* The states the KCS driver may be in. */
 enum kcs_states {
 	/* The KCS interface is currently doing nothing. */
 	KCS_IDLE,

 	/*
 	 * We are starting an operation.  The data is in the output
 	 * buffer, but nothing has been done to the interface yet.  This
 	 * was added to the state machine in the spec to wait for the
 	 * initial IBF.
 	 */
 	KCS_START_OP,

 	/* We have written a write cmd to the interface. */
 	KCS_WAIT_WRITE_START,

 	/* We are writing bytes to the interface. */
 	KCS_WAIT_WRITE,

 	/*
 	 * We have written the write end cmd to the interface, and
 	 * still need to write the last byte.
 	 */
 	KCS_WAIT_WRITE_END,

 	/* We are waiting to read data from the interface. */
 	KCS_WAIT_READ,

 	/*
 	 * State to transition to the error handler, this was added to
 	 * the state machine in the spec to be sure IBF was there.
 	 */
 	KCS_ERROR0,

 	/*
 	 * First stage error handler, wait for the interface to
 	 * respond.
 	 */
 	KCS_ERROR1,

 	/*
 	 * The abort cmd has been written, wait for the interface to
 	 * respond.
 	 */
 	KCS_ERROR2,

 	/*
 	 * We wrote some data to the interface, wait for it to switch
 	 * to read mode.
 	 */
 	KCS_ERROR3,

 	/* The hardware failed to follow the state machine. */
 	KCS_HOSED
 };

 #define MAX_KCS_READ_SIZE IPMI_MAX_MSG_LENGTH
 #define MAX_KCS_WRITE_SIZE IPMI_MAX_MSG_LENGTH

 /* Timeouts in microseconds. */
 #define IBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
 #define OBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
 #define MAX_ERROR_RETRIES 10
 #define ERROR0_OBF_WAIT_JIFFIES (2*HZ)

 struct si_sm_data {
 	enum kcs_states  state;
 	struct si_sm_io *io;
 	unsigned char    write_data[MAX_KCS_WRITE_SIZE];
 	int              write_pos;
 	int              write_count;
 	int              orig_write_count;
 	unsigned char    read_data[MAX_KCS_READ_SIZE];
 	int              read_pos;
 	int	         truncated;

 	unsigned int  error_retries;
 	long          ibf_timeout;
 	long          obf_timeout;
 	unsigned long  error0_timeout;
 };

 static unsigned int init_kcs_data(struct si_sm_data *kcs,
 				  struct si_sm_io *io)
 {
 	kcs->state = KCS_IDLE;
 	kcs->io = io;
 	kcs->write_pos = 0;
 	kcs->write_count = 0;
 	kcs->orig_write_count = 0;
 	kcs->read_pos = 0;
 	kcs->error_retries = 0;
 	kcs->truncated = 0;
 	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 	kcs->obf_timeout = OBF_RETRY_TIMEOUT;

 	/* Reserve 2 I/O bytes. */
 	return 2;
 }

 static inline unsigned char read_status(struct si_sm_data *kcs)
 {
 	return kcs->io->inputb(kcs->io, 1);
 }

 static inline unsigned char read_data(struct si_sm_data *kcs)
 {
 	return kcs->io->inputb(kcs->io, 0);
 }

 static inline void write_cmd(struct si_sm_data *kcs, unsigned char data)
 {
 	kcs->io->outputb(kcs->io, 1, data);
 }

 static inline void write_data(struct si_sm_data *kcs, unsigned char data)
 {
 	kcs->io->outputb(kcs->io, 0, data);
 }

 /* Control codes. */
 #define KCS_GET_STATUS_ABORT	0x60
 #define KCS_WRITE_START		0x61
 #define KCS_WRITE_END		0x62
 #define KCS_READ_BYTE		0x68

 /* Status bits. */
 #define GET_STATUS_STATE(status) (((status) >> 6) & 0x03)
 #define KCS_IDLE_STATE	0
 #define KCS_READ_STATE	1
 #define KCS_WRITE_STATE	2
 #define KCS_ERROR_STATE	3
 #define GET_STATUS_ATN(status) ((status) & 0x04)
 #define GET_STATUS_IBF(status) ((status) & 0x02)
 #define GET_STATUS_OBF(status) ((status) & 0x01)


 static inline void write_next_byte(struct si_sm_data *kcs)
 {
 	write_data(kcs, kcs->write_data[kcs->write_pos]);
 	(kcs->write_pos)++;
 	(kcs->write_count)--;
 }

 static inline void start_error_recovery(struct si_sm_data *kcs, char *reason)
 {
 	(kcs->error_retries)++;
 	if (kcs->error_retries > MAX_ERROR_RETRIES) {
 		if (kcs_debug & KCS_DEBUG_ENABLE)
 			printk(KERN_DEBUG "ipmi_kcs_sm: kcs hosed: %s\n",
 			       reason);
 		kcs->state = KCS_HOSED;
 	} else {
 		kcs->error0_timeout = jiffies + ERROR0_OBF_WAIT_JIFFIES;
 		kcs->state = KCS_ERROR0;
 	}
 }

 static inline void read_next_byte(struct si_sm_data *kcs)
 {
 	if (kcs->read_pos >= MAX_KCS_READ_SIZE) {
 		/* Throw the data away and mark it truncated. */
 		read_data(kcs);
 		kcs->truncated = 1;
 	} else {
 		kcs->read_data[kcs->read_pos] = read_data(kcs);
 		(kcs->read_pos)++;
 	}
 	write_data(kcs, KCS_READ_BYTE);
 }

 static inline int check_ibf(struct si_sm_data *kcs, unsigned char status,
 			    long time)
 {
 	if (GET_STATUS_IBF(status)) {
 		kcs->ibf_timeout -= time;
 		if (kcs->ibf_timeout < 0) {
 			start_error_recovery(kcs, "IBF not ready in time");
 			kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 			return 1;
 		}
 		return 0;
 	}
 	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 	return 1;
 }

 static inline int check_obf(struct si_sm_data *kcs, unsigned char status,
 			    long time)
 {
 	if (!GET_STATUS_OBF(status)) {
 		kcs->obf_timeout -= time;
 		if (kcs->obf_timeout < 0) {
 			kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 			start_error_recovery(kcs, "OBF not ready in time");
 			return 1;
 		}
 		return 0;
 	}
 	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 	return 1;
 }

 static void clear_obf(struct si_sm_data *kcs, unsigned char status)
 {
 	if (GET_STATUS_OBF(status))
 		read_data(kcs);
 }

 static void restart_kcs_transaction(struct si_sm_data *kcs)
 {
 	kcs->write_count = kcs->orig_write_count;
 	kcs->write_pos = 0;
 	kcs->read_pos = 0;
 	kcs->state = KCS_WAIT_WRITE_START;
 	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 	write_cmd(kcs, KCS_WRITE_START);
 }

 static int start_kcs_transaction(struct si_sm_data *kcs, unsigned char *data,
 				 unsigned int size)
 {
 	unsigned int i;

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

 	if ((kcs->state != KCS_IDLE) && (kcs->state != KCS_HOSED))
 		return IPMI_NOT_IN_MY_STATE_ERR;

 	if (kcs_debug & KCS_DEBUG_MSG) {
 		printk(KERN_DEBUG "start_kcs_transaction -");
 		for (i = 0; i < size; i++)
 			pr_cont(" %02x", data[i]);
 		pr_cont("\n");
 	}
 	kcs->error_retries = 0;
 	memcpy(kcs->write_data, data, size);
 	kcs->write_count = size;
 	kcs->orig_write_count = size;
 	kcs->write_pos = 0;
 	kcs->read_pos = 0;
 	kcs->state = KCS_START_OP;
 	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 	return 0;
 }

 static int get_kcs_result(struct si_sm_data *kcs, unsigned char *data,
 			  unsigned int length)
 {
 	if (length < kcs->read_pos) {
 		kcs->read_pos = length;
 		kcs->truncated = 1;
 	}

 	memcpy(data, kcs->read_data, kcs->read_pos);

 	if ((length >= 3) && (kcs->read_pos < 3)) {
 		/* Guarantee that we return at least 3 bytes, with an
 		   error in the third byte if it is too short. */
 		data[2] = IPMI_ERR_UNSPECIFIED;
 		kcs->read_pos = 3;
 	}
 	if (kcs->truncated) {
 		/*
 		 * Report a truncated error.  We might overwrite
 		 * another error, but that's too bad, the user needs
 		 * to know it was truncated.
 		 */
 		data[2] = IPMI_ERR_MSG_TRUNCATED;
 		kcs->truncated = 0;
 	}

 	return kcs->read_pos;
 }

 /*
  * This implements the state machine defined in the IPMI manual, see
  * that for details on how this works.  Divide that flowchart into
  * sections delimited by "Wait for IBF" and this will become clear.
  */
 static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
 {
 	unsigned char status;
 	unsigned char state;

 	status = read_status(kcs);

 	if (kcs_debug & KCS_DEBUG_STATES)
 		printk(KERN_DEBUG "KCS: State = %d, %x\n", kcs->state, status);

 	/* All states wait for ibf, so just do it here. */
 	if (!check_ibf(kcs, status, time))
 		return SI_SM_CALL_WITH_DELAY;

 	/* Just about everything looks at the KCS state, so grab that, too. */
 	state = GET_STATUS_STATE(status);

 	switch (kcs->state) {
 	case KCS_IDLE:
 		/* If there's and interrupt source, turn it off. */
 		clear_obf(kcs, status);

 		if (GET_STATUS_ATN(status))
 			return SI_SM_ATTN;
 		else
 			return SI_SM_IDLE;

 	case KCS_START_OP:
 		if (state != KCS_IDLE_STATE) {
 			start_error_recovery(kcs,
 					     "State machine not idle at start");
 			break;
 		}

 		clear_obf(kcs, status);
 		write_cmd(kcs, KCS_WRITE_START);
 		kcs->state = KCS_WAIT_WRITE_START;
 		break;

 	case KCS_WAIT_WRITE_START:
 		if (state != KCS_WRITE_STATE) {
 			start_error_recovery(
 				kcs,
 				"Not in write state at write start");
 			break;
 		}
 		read_data(kcs);
 		if (kcs->write_count == 1) {
 			write_cmd(kcs, KCS_WRITE_END);
 			kcs->state = KCS_WAIT_WRITE_END;
 		} else {
 			write_next_byte(kcs);
 			kcs->state = KCS_WAIT_WRITE;
 		}
 		break;

 	case KCS_WAIT_WRITE:
 		if (state != KCS_WRITE_STATE) {
 			start_error_recovery(kcs,
 					     "Not in write state for write");
 			break;
 		}
 		clear_obf(kcs, status);
 		if (kcs->write_count == 1) {
 			write_cmd(kcs, KCS_WRITE_END);
 			kcs->state = KCS_WAIT_WRITE_END;
 		} else {
 			write_next_byte(kcs);
 		}
 		break;

 	case KCS_WAIT_WRITE_END:
 		if (state != KCS_WRITE_STATE) {
 			start_error_recovery(kcs,
 					     "Not in write state"
 					     " for write end");
 			break;
 		}
 		clear_obf(kcs, status);
 		write_next_byte(kcs);
 		kcs->state = KCS_WAIT_READ;
 		break;

 	case KCS_WAIT_READ:
 		if ((state != KCS_READ_STATE) && (state != KCS_IDLE_STATE)) {
 			start_error_recovery(
 				kcs,
 				"Not in read or idle in read state");
 			break;
 		}

 		if (state == KCS_READ_STATE) {
 			if (!check_obf(kcs, status, time))
 				return SI_SM_CALL_WITH_DELAY;
 			read_next_byte(kcs);
 		} else {
 			/*
 			 * We don't implement this exactly like the state
 			 * machine in the spec.  Some broken hardware
 			 * does not write the final dummy byte to the
 			 * read register.  Thus obf will never go high
 			 * here.  We just go straight to idle, and we
 			 * handle clearing out obf in idle state if it
 			 * happens to come in.
 			 */
 			clear_obf(kcs, status);
 			kcs->orig_write_count = 0;
 			kcs->state = KCS_IDLE;
 			return SI_SM_TRANSACTION_COMPLETE;
 		}
 		break;

 	case KCS_ERROR0:
 		clear_obf(kcs, status);
 		status = read_status(kcs);
 		if (GET_STATUS_OBF(status))
 			/* controller isn't responding */
 			if (time_before(jiffies, kcs->error0_timeout))
 				return SI_SM_CALL_WITH_TICK_DELAY;
 		write_cmd(kcs, KCS_GET_STATUS_ABORT);
 		kcs->state = KCS_ERROR1;
 		break;

 	case KCS_ERROR1:
 		clear_obf(kcs, status);
 		write_data(kcs, 0);
 		kcs->state = KCS_ERROR2;
 		break;

 	case KCS_ERROR2:
 		if (state != KCS_READ_STATE) {
 			start_error_recovery(kcs,
 					     "Not in read state for error2");
 			break;
 		}
 		if (!check_obf(kcs, status, time))
 			return SI_SM_CALL_WITH_DELAY;

 		clear_obf(kcs, status);
 		write_data(kcs, KCS_READ_BYTE);
 		kcs->state = KCS_ERROR3;
 		break;

 	case KCS_ERROR3:
 		if (state != KCS_IDLE_STATE) {
 			start_error_recovery(kcs,
 					     "Not in idle state for error3");
 			break;
 		}

 		if (!check_obf(kcs, status, time))
 			return SI_SM_CALL_WITH_DELAY;

 		clear_obf(kcs, status);
 		if (kcs->orig_write_count) {
 			restart_kcs_transaction(kcs);
 		} else {
 			kcs->state = KCS_IDLE;
 			return SI_SM_TRANSACTION_COMPLETE;
 		}
 		break;

 	case KCS_HOSED:
 		break;
 	}

 	if (kcs->state == KCS_HOSED) {
 		init_kcs_data(kcs, kcs->io);
 		return SI_SM_HOSED;
 	}

 	return SI_SM_CALL_WITHOUT_DELAY;
 }

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

 static int kcs_detect(struct si_sm_data *kcs)
 {
 	/*
 	 * It's impossible for the KCS status register 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.
 	 */
 	if (read_status(kcs) == 0xff)
 		return 1;

 	return 0;
 }

 static void kcs_cleanup(struct si_sm_data *kcs)
 {
 }

 const struct si_sm_handlers kcs_smi_handlers = {
 	.init_data         = init_kcs_data,
 	.start_transaction = start_kcs_transaction,
 	.get_result        = get_kcs_result,
 	.event             = kcs_event,
 	.detect            = kcs_detect,
 	.cleanup           = kcs_cleanup,
 	.size              = kcs_size,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* ipmi_kcs_sm.c
	*
	* State machine for handling IPMI KCS interfaces.
	*
	* Author: MontaVista Software, Inc.
	* Corey Minyard <minyard@mvista.com>
	* source@mvista.com
	*
	* Copyright 2002 MontaVista Software Inc.
	*/

	/*
	* This state machine is taken from the state machine in the IPMI spec,
	* pretty much verbatim. If you have questions about the states, see
	* that document.
	*/

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

	/* kcs_debug is a bit-field
	* KCS_DEBUG_ENABLE - turned on for now
	* KCS_DEBUG_MSG - commands and their responses
	* KCS_DEBUG_STATES - state machine
	*/
	#define KCS_DEBUG_STATES 4
	#define KCS_DEBUG_MSG 2
	#define KCS_DEBUG_ENABLE 1

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

	/* The states the KCS driver may be in. */
	enum kcs_states {
	/* The KCS interface is currently doing nothing. */
	KCS_IDLE,

	/*
	* We are starting an operation. The data is in the output
	* buffer, but nothing has been done to the interface yet. This
	* was added to the state machine in the spec to wait for the
	* initial IBF.
	*/
	KCS_START_OP,

	/* We have written a write cmd to the interface. */
	KCS_WAIT_WRITE_START,

	/* We are writing bytes to the interface. */
	KCS_WAIT_WRITE,

	/*
	* We have written the write end cmd to the interface, and
	* still need to write the last byte.
	*/
	KCS_WAIT_WRITE_END,

	/* We are waiting to read data from the interface. */
	KCS_WAIT_READ,

	/*
	* State to transition to the error handler, this was added to
	* the state machine in the spec to be sure IBF was there.
	*/
	KCS_ERROR0,

	/*
	* First stage error handler, wait for the interface to
	* respond.
	*/
	KCS_ERROR1,

	/*
	* The abort cmd has been written, wait for the interface to
	* respond.
	*/
	KCS_ERROR2,

	/*
	* We wrote some data to the interface, wait for it to switch
	* to read mode.
	*/
	KCS_ERROR3,

	/* The hardware failed to follow the state machine. */
	KCS_HOSED
	};

	#define MAX_KCS_READ_SIZE IPMI_MAX_MSG_LENGTH
	#define MAX_KCS_WRITE_SIZE IPMI_MAX_MSG_LENGTH

	/* Timeouts in microseconds. */
	#define IBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
	#define OBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
	#define MAX_ERROR_RETRIES 10
	#define ERROR0_OBF_WAIT_JIFFIES (2*HZ)

	struct si_sm_data {
	enum kcs_states state;
	struct si_sm_io *io;
	unsigned char write_data[MAX_KCS_WRITE_SIZE];
	int write_pos;
	int write_count;
	int orig_write_count;
	unsigned char read_data[MAX_KCS_READ_SIZE];
	int read_pos;
	int truncated;

	unsigned int error_retries;
	long ibf_timeout;
	long obf_timeout;
	unsigned long error0_timeout;
	};

	static unsigned int init_kcs_data(struct si_sm_data *kcs,
	struct si_sm_io *io)
	{
	kcs->state = KCS_IDLE;
	kcs->io = io;
	kcs->write_pos = 0;
	kcs->write_count = 0;
	kcs->orig_write_count = 0;
	kcs->read_pos = 0;
	kcs->error_retries = 0;
	kcs->truncated = 0;
	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
	kcs->obf_timeout = OBF_RETRY_TIMEOUT;

	/* Reserve 2 I/O bytes. */
	return 2;
	}

	static inline unsigned char read_status(struct si_sm_data *kcs)
	{
	return kcs->io->inputb(kcs->io, 1);
	}

	static inline unsigned char read_data(struct si_sm_data *kcs)
	{
	return kcs->io->inputb(kcs->io, 0);
	}

	static inline void write_cmd(struct si_sm_data *kcs, unsigned char data)
	{
	kcs->io->outputb(kcs->io, 1, data);
	}

	static inline void write_data(struct si_sm_data *kcs, unsigned char data)
	{
	kcs->io->outputb(kcs->io, 0, data);
	}

	/* Control codes. */
	#define KCS_GET_STATUS_ABORT 0x60
	#define KCS_WRITE_START 0x61
	#define KCS_WRITE_END 0x62
	#define KCS_READ_BYTE 0x68

	/* Status bits. */
	#define GET_STATUS_STATE(status) (((status) >> 6) & 0x03)
	#define KCS_IDLE_STATE 0
	#define KCS_READ_STATE 1
	#define KCS_WRITE_STATE 2
	#define KCS_ERROR_STATE 3
	#define GET_STATUS_ATN(status) ((status) & 0x04)
	#define GET_STATUS_IBF(status) ((status) & 0x02)
	#define GET_STATUS_OBF(status) ((status) & 0x01)


	static inline void write_next_byte(struct si_sm_data *kcs)
	{
	write_data(kcs, kcs->write_data[kcs->write_pos]);
	(kcs->write_pos)++;
	(kcs->write_count)--;
	}

	static inline void start_error_recovery(struct si_sm_data kcs, char reason)
	{
	(kcs->error_retries)++;
	if (kcs->error_retries > MAX_ERROR_RETRIES) {
	if (kcs_debug & KCS_DEBUG_ENABLE)
	printk(KERN_DEBUG "ipmi_kcs_sm: kcs hosed: %s\n",
	reason);
	kcs->state = KCS_HOSED;
	} else {
	kcs->error0_timeout = jiffies + ERROR0_OBF_WAIT_JIFFIES;
	kcs->state = KCS_ERROR0;
	}
	}

	static inline void read_next_byte(struct si_sm_data *kcs)
	{
	if (kcs->read_pos >= MAX_KCS_READ_SIZE) {
	/* Throw the data away and mark it truncated. */
	read_data(kcs);
	kcs->truncated = 1;
	} else {
	kcs->read_data[kcs->read_pos] = read_data(kcs);
	(kcs->read_pos)++;
	}
	write_data(kcs, KCS_READ_BYTE);
	}

	static inline int check_ibf(struct si_sm_data *kcs, unsigned char status,
	long time)
	{
	if (GET_STATUS_IBF(status)) {
	kcs->ibf_timeout -= time;
	if (kcs->ibf_timeout < 0) {
	start_error_recovery(kcs, "IBF not ready in time");
	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
	return 1;
	}
	return 0;
	}
	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
	return 1;
	}

	static inline int check_obf(struct si_sm_data *kcs, unsigned char status,
	long time)
	{
	if (!GET_STATUS_OBF(status)) {
	kcs->obf_timeout -= time;
	if (kcs->obf_timeout < 0) {
	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
	start_error_recovery(kcs, "OBF not ready in time");
	return 1;
	}
	return 0;
	}
	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
	return 1;
	}

	static void clear_obf(struct si_sm_data *kcs, unsigned char status)
	{
	if (GET_STATUS_OBF(status))
	read_data(kcs);
	}

	static void restart_kcs_transaction(struct si_sm_data *kcs)
	{
	kcs->write_count = kcs->orig_write_count;
	kcs->write_pos = 0;
	kcs->read_pos = 0;
	kcs->state = KCS_WAIT_WRITE_START;
	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
	write_cmd(kcs, KCS_WRITE_START);
	}

	static int start_kcs_transaction(struct si_sm_data kcs, unsigned char data,
	unsigned int size)
	{
	unsigned int i;

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

	if ((kcs->state != KCS_IDLE) && (kcs->state != KCS_HOSED))
	return IPMI_NOT_IN_MY_STATE_ERR;

	if (kcs_debug & KCS_DEBUG_MSG) {
	printk(KERN_DEBUG "start_kcs_transaction -");
	for (i = 0; i < size; i++)
	pr_cont(" %02x", data[i]);
	pr_cont("\n");
	}
	kcs->error_retries = 0;
	memcpy(kcs->write_data, data, size);
	kcs->write_count = size;
	kcs->orig_write_count = size;
	kcs->write_pos = 0;
	kcs->read_pos = 0;
	kcs->state = KCS_START_OP;
	kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
	kcs->obf_timeout = OBF_RETRY_TIMEOUT;
	return 0;
	}

	static int get_kcs_result(struct si_sm_data kcs, unsigned char data,
	unsigned int length)
	{
	if (length < kcs->read_pos) {
	kcs->read_pos = length;
	kcs->truncated = 1;
	}

	memcpy(data, kcs->read_data, kcs->read_pos);

	if ((length >= 3) && (kcs->read_pos < 3)) {
	/* Guarantee that we return at least 3 bytes, with an
	error in the third byte if it is too short. */
	data[2] = IPMI_ERR_UNSPECIFIED;
	kcs->read_pos = 3;
	}
	if (kcs->truncated) {
	/*
	* Report a truncated error. We might overwrite
	* another error, but that's too bad, the user needs
	* to know it was truncated.
	*/
	data[2] = IPMI_ERR_MSG_TRUNCATED;
	kcs->truncated = 0;
	}

	return kcs->read_pos;
	}

	/*
	* This implements the state machine defined in the IPMI manual, see
	* that for details on how this works. Divide that flowchart into
	* sections delimited by "Wait for IBF" and this will become clear.
	*/
	static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
	{
	unsigned char status;
	unsigned char state;

	status = read_status(kcs);

	if (kcs_debug & KCS_DEBUG_STATES)
	printk(KERN_DEBUG "KCS: State = %d, %x\n", kcs->state, status);

	/* All states wait for ibf, so just do it here. */
	if (!check_ibf(kcs, status, time))
	return SI_SM_CALL_WITH_DELAY;

	/* Just about everything looks at the KCS state, so grab that, too. */
	state = GET_STATUS_STATE(status);

	switch (kcs->state) {
	case KCS_IDLE:
	/* If there's and interrupt source, turn it off. */
	clear_obf(kcs, status);

	if (GET_STATUS_ATN(status))
	return SI_SM_ATTN;
	else
	return SI_SM_IDLE;

	case KCS_START_OP:
	if (state != KCS_IDLE_STATE) {
	start_error_recovery(kcs,
	"State machine not idle at start");
	break;
	}

	clear_obf(kcs, status);
	write_cmd(kcs, KCS_WRITE_START);
	kcs->state = KCS_WAIT_WRITE_START;
	break;

	case KCS_WAIT_WRITE_START:
	if (state != KCS_WRITE_STATE) {
	start_error_recovery(
	kcs,
	"Not in write state at write start");
	break;
	}
	read_data(kcs);
	if (kcs->write_count == 1) {
	write_cmd(kcs, KCS_WRITE_END);
	kcs->state = KCS_WAIT_WRITE_END;
	} else {
	write_next_byte(kcs);
	kcs->state = KCS_WAIT_WRITE;
	}
	break;

	case KCS_WAIT_WRITE:
	if (state != KCS_WRITE_STATE) {
	start_error_recovery(kcs,
	"Not in write state for write");
	break;
	}
	clear_obf(kcs, status);
	if (kcs->write_count == 1) {
	write_cmd(kcs, KCS_WRITE_END);
	kcs->state = KCS_WAIT_WRITE_END;
	} else {
	write_next_byte(kcs);
	}
	break;

	case KCS_WAIT_WRITE_END:
	if (state != KCS_WRITE_STATE) {
	start_error_recovery(kcs,
	"Not in write state"
	" for write end");
	break;
	}
	clear_obf(kcs, status);
	write_next_byte(kcs);
	kcs->state = KCS_WAIT_READ;
	break;

	case KCS_WAIT_READ:
	if ((state != KCS_READ_STATE) && (state != KCS_IDLE_STATE)) {
	start_error_recovery(
	kcs,
	"Not in read or idle in read state");
	break;
	}

	if (state == KCS_READ_STATE) {
	if (!check_obf(kcs, status, time))
	return SI_SM_CALL_WITH_DELAY;
	read_next_byte(kcs);
	} else {
	/*
	* We don't implement this exactly like the state
	* machine in the spec. Some broken hardware
	* does not write the final dummy byte to the
	* read register. Thus obf will never go high
	* here. We just go straight to idle, and we
	* handle clearing out obf in idle state if it
	* happens to come in.
	*/
	clear_obf(kcs, status);
	kcs->orig_write_count = 0;
	kcs->state = KCS_IDLE;
	return SI_SM_TRANSACTION_COMPLETE;
	}
	break;

	case KCS_ERROR0:
	clear_obf(kcs, status);
	status = read_status(kcs);
	if (GET_STATUS_OBF(status))
	/* controller isn't responding */
	if (time_before(jiffies, kcs->error0_timeout))
	return SI_SM_CALL_WITH_TICK_DELAY;
	write_cmd(kcs, KCS_GET_STATUS_ABORT);
	kcs->state = KCS_ERROR1;
	break;

	case KCS_ERROR1:
	clear_obf(kcs, status);
	write_data(kcs, 0);
	kcs->state = KCS_ERROR2;
	break;

	case KCS_ERROR2:
	if (state != KCS_READ_STATE) {
	start_error_recovery(kcs,
	"Not in read state for error2");
	break;
	}
	if (!check_obf(kcs, status, time))
	return SI_SM_CALL_WITH_DELAY;

	clear_obf(kcs, status);
	write_data(kcs, KCS_READ_BYTE);
	kcs->state = KCS_ERROR3;
	break;

	case KCS_ERROR3:
	if (state != KCS_IDLE_STATE) {
	start_error_recovery(kcs,
	"Not in idle state for error3");
	break;
	}

	if (!check_obf(kcs, status, time))
	return SI_SM_CALL_WITH_DELAY;

	clear_obf(kcs, status);
	if (kcs->orig_write_count) {
	restart_kcs_transaction(kcs);
	} else {
	kcs->state = KCS_IDLE;
	return SI_SM_TRANSACTION_COMPLETE;
	}
	break;

	case KCS_HOSED:
	break;
	}

	if (kcs->state == KCS_HOSED) {
	init_kcs_data(kcs, kcs->io);
	return SI_SM_HOSED;
	}

	return SI_SM_CALL_WITHOUT_DELAY;
	}

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

	static int kcs_detect(struct si_sm_data *kcs)
	{
	/*
	* It's impossible for the KCS status register 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.
	*/
	if (read_status(kcs) == 0xff)
	return 1;

	return 0;
	}

	static void kcs_cleanup(struct si_sm_data *kcs)
	{
	}

	const struct si_sm_handlers kcs_smi_handlers = {
	.init_data = init_kcs_data,
	.start_transaction = start_kcs_transaction,
	.get_result = get_kcs_result,
	.event = kcs_event,
	.detect = kcs_detect,
	.cleanup = kcs_cleanup,
	.size = kcs_size,
	};