// SPDX-License-Identifier: GPL-2.0+

  /*

   * (C) Copyright 2000-2004

   * Wolfgang Denk, DENX Software Engineering, wd@denx.de.

   */
  
  /*
   * Serial up- and download support
   */
  #include <common.h>
  #include <command.h>

  #include <console.h>

  #include <cpu_func.h>

  #include <efi_loader.h>

  #include <env.h>

  #include <exports.h>

  #include <flash.h>

  #include <image.h>

  #include <lmb.h>

  #include <mapmem.h>

  #include <net.h>

  #include <s_record.h>

  #include <serial.h>

  #include <xyzModem.h>

  #include <asm/cache.h>

  #include <asm/global_data.h>

  #include <linux/delay.h>

  DECLARE_GLOBAL_DATA_PTR;

  #if defined(CONFIG_CMD_LOADB)

  static ulong load_serial_ymodem(ulong offset, int mode);

  #endif

  #if defined(CONFIG_CMD_LOADS)

  static ulong load_serial(long offset);
  static int read_record(char *buf, ulong len);

  # if defined(CONFIG_CMD_SAVES)

  static int save_serial(ulong offset, ulong size);
  static int write_record(char *buf);

  #endif

  
  static int do_echo = 1;

  #endif

  
  /* -------------------------------------------------------------------- */

  #if defined(CONFIG_CMD_LOADS)

  static int do_load_serial(struct cmd_tbl *cmdtp, int flag, int argc,
  			  char *const argv[])

  {

  	long offset = 0;

  	ulong addr;
  	int i;
  	char *env_echo;
  	int rcode = 0;

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	int load_baudrate, current_baudrate;
  
  	load_baudrate = current_baudrate = gd->baudrate;
  #endif

  	env_echo = env_get("loads_echo");
  	if (env_echo && *env_echo == '1')

  		do_echo = 1;

  	else

  		do_echo = 0;

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	if (argc >= 2) {

  		offset = simple_strtol(argv[1], NULL, 16);

  	}
  	if (argc == 3) {

  		load_baudrate = (int)dectoul(argv[2], NULL);

  
  		/* default to current baudrate */
  		if (load_baudrate == 0)
  			load_baudrate = current_baudrate;
  	}
  	if (load_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ENTER ...
  ",

  			load_baudrate);
  		udelay(50000);
  		gd->baudrate = load_baudrate;

  		serial_setbrg();

  		udelay(50000);
  		for (;;) {

  			if (getchar() == '\r')

  				break;
  		}
  	}

  #else	/* ! CONFIG_SYS_LOADS_BAUD_CHANGE */

  	if (argc == 2) {

  		offset = simple_strtol(argv[1], NULL, 16);

  	}

  #endif	/* CONFIG_SYS_LOADS_BAUD_CHANGE */

  	printf("## Ready for S-Record download ...
  ");

  	addr = load_serial(offset);

  
  	/*
  	 * Gather any trailing characters (for instance, the ^D which
  	 * is sent by 'cu' after sending a file), and give the
  	 * box some time (100 * 1 ms)
  	 */
  	for (i=0; i<100; ++i) {

  		if (tstc()) {

  			getchar();

  		}
  		udelay(1000);
  	}
  
  	if (addr == ~0) {

  		printf("## S-Record download aborted
  ");

  		rcode = 1;
  	} else {

  		printf("## Start Addr      = 0x%08lX
  ", addr);

  		image_load_addr = addr;

  	}

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	if (load_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ESC ...
  ",

  			current_baudrate);

  		udelay(50000);

  		gd->baudrate = current_baudrate;

  		serial_setbrg();
  		udelay(50000);

  		for (;;) {

  			if (getchar() == 0x1B) /* ESC */

  				break;
  		}
  	}
  #endif
  	return rcode;
  }

  static ulong load_serial(long offset)

  {

  	struct lmb lmb;

  	char	record[SREC_MAXRECLEN + 1];	/* buffer for one S-Record	*/
  	char	binbuf[SREC_MAXBINLEN];		/* buffer for binary data	*/
  	int	binlen;				/* no. of data bytes in S-Rec.	*/
  	int	type;				/* return code for record type	*/
  	ulong	addr;				/* load address from S-Record	*/
  	ulong	size;				/* number of bytes transferred	*/

  	ulong	store_addr;
  	ulong	start_addr = ~0;
  	ulong	end_addr   =  0;
  	int	line_count =  0;

  	long ret;
  
  	lmb_init_and_reserve(&lmb, gd->bd, (void *)gd->fdt_blob);

  
  	while (read_record(record, SREC_MAXRECLEN + 1) >= 0) {

  		type = srec_decode(record, &binlen, &addr, binbuf);

  
  		if (type < 0) {
  			return (~0);		/* Invalid S-Record		*/
  		}
  
  		switch (type) {
  		case SREC_DATA2:
  		case SREC_DATA3:
  		case SREC_DATA4:
  		    store_addr = addr + offset;

  #ifdef CONFIG_MTD_NOR_FLASH

  		    if (addr2info(store_addr)) {
  			int rc;

  			rc = flash_write((char *)binbuf,store_addr,binlen);

  			if (rc != 0) {

  				flash_perror(rc);

  				return (~0);
  			}
  		    } else
  #endif
  		    {

  			ret = lmb_reserve(&lmb, store_addr, binlen);
  			if (ret) {
  				printf("
  Cannot overwrite reserved area (%08lx..%08lx)
  ",
  					store_addr, store_addr + binlen);
  				return ret;
  			}

  			memcpy((char *)(store_addr), binbuf, binlen);

  			lmb_free(&lmb, store_addr, binlen);

  		    }
  		    if ((store_addr) < start_addr)
  			start_addr = store_addr;
  		    if ((store_addr + binlen - 1) > end_addr)
  			end_addr = store_addr + binlen - 1;
  		    break;
  		case SREC_END2:
  		case SREC_END3:
  		case SREC_END4:

  		    udelay(10000);

  		    size = end_addr - start_addr + 1;

  		    printf("
  "

  			    "## First Load Addr = 0x%08lX
  "
  			    "## Last  Load Addr = 0x%08lX
  "
  			    "## Total Size      = 0x%08lX = %ld Bytes
  ",
  			    start_addr, end_addr, size, size
  		    );

  		    flush_cache(start_addr, size);

  		    env_set_hex("filesize", size);

  		    return (addr);
  		case SREC_START:
  		    break;
  		default:
  		    break;
  		}
  		if (!do_echo) {	/* print a '.' every 100 lines */
  			if ((++line_count % 100) == 0)

  				putc('.');

  		}
  	}
  
  	return (~0);			/* Download aborted		*/
  }

  static int read_record(char *buf, ulong len)

  {
  	char *p;
  	char c;
  
  	--len;	/* always leave room for terminating '\0' byte */
  
  	for (p=buf; p < buf+len; ++p) {

  		c = getchar();		/* read character		*/

  		if (do_echo)

  			putc(c);	/* ... and echo it		*/

  
  		switch (c) {
  		case '\r':
  		case '
  ':
  			*p = '\0';
  			return (p - buf);
  		case '\0':
  		case 0x03:			/* ^C - Control C		*/
  			return (-1);
  		default:
  			*p = c;
  		}

  		/* Check for the console hangup (if any different from serial) */
  		if (gd->jt->getc != getchar) {
  			if (ctrlc())
  				return (-1);

  		}

  	}
  
  	/* line too long - truncate */
  	*p = '\0';
  	return (p - buf);
  }

  #if defined(CONFIG_CMD_SAVES)

  int do_save_serial(struct cmd_tbl *cmdtp, int flag, int argc,
  		   char *const argv[])

  {
  	ulong offset = 0;
  	ulong size   = 0;

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	int save_baudrate, current_baudrate;
  
  	save_baudrate = current_baudrate = gd->baudrate;
  #endif
  
  	if (argc >= 2) {

  		offset = hextoul(argv[1], NULL);

  	}

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	if (argc >= 3) {

  		size = hextoul(argv[2], NULL);

  	}
  	if (argc == 4) {

  		save_baudrate = (int)dectoul(argv[3], NULL);

  
  		/* default to current baudrate */
  		if (save_baudrate == 0)
  			save_baudrate = current_baudrate;
  	}
  	if (save_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ENTER ...
  ",

  			save_baudrate);
  		udelay(50000);
  		gd->baudrate = save_baudrate;

  		serial_setbrg();

  		udelay(50000);
  		for (;;) {

  			if (getchar() == '\r')

  				break;
  		}
  	}

  #else	/* ! CONFIG_SYS_LOADS_BAUD_CHANGE */

  	if (argc == 3) {

  		size = hextoul(argv[2], NULL);

  	}

  #endif	/* CONFIG_SYS_LOADS_BAUD_CHANGE */

  	printf("## Ready for S-Record upload, press ENTER to proceed ...
  ");

  	for (;;) {

  		if (getchar() == '\r')

  			break;
  	}

  	if (save_serial(offset, size)) {
  		printf("## S-Record upload aborted
  ");

  	} else {

  		printf("## S-Record upload complete
  ");

  	}

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  	if (save_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ESC ...
  ",

  			(int)current_baudrate);

  		udelay(50000);

  		gd->baudrate = current_baudrate;

  		serial_setbrg();
  		udelay(50000);

  		for (;;) {

  			if (getchar() == 0x1B) /* ESC */

  				break;
  		}
  	}
  #endif
  	return 0;
  }
  
  #define SREC3_START				"S0030000FC
  "
  #define SREC3_FORMAT			"S3%02X%08lX%s%02X
  "
  #define SREC3_END				"S70500000000FA
  "
  #define SREC_BYTES_PER_RECORD	16

  static int save_serial(ulong address, ulong count)

  {
  	int i, c, reclen, checksum, length;
  	char *hex = "0123456789ABCDEF";
  	char	record[2*SREC_BYTES_PER_RECORD+16];	/* buffer for one S-Record	*/
  	char	data[2*SREC_BYTES_PER_RECORD+1];	/* buffer for hex data	*/
  
  	reclen = 0;
  	checksum  = 0;
  
  	if(write_record(SREC3_START))			/* write the header */
  		return (-1);
  	do {
  		if(count) {						/* collect hex data in the buffer  */
  			c = *(volatile uchar*)(address + reclen);	/* get one byte    */
  			checksum += c;							/* accumulate checksum */
  			data[2*reclen]   = hex[(c>>4)&0x0f];
  			data[2*reclen+1] = hex[c & 0x0f];
  			data[2*reclen+2] = '\0';
  			++reclen;
  			--count;
  		}
  		if(reclen == SREC_BYTES_PER_RECORD || count == 0) {
  			/* enough data collected for one record: dump it */
  			if(reclen) {	/* build & write a data record: */
  				/* address + data + checksum */
  				length = 4 + reclen + 1;
  
  				/* accumulate length bytes into checksum */
  				for(i = 0; i < 2; i++)
  					checksum += (length >> (8*i)) & 0xff;
  
  				/* accumulate address bytes into checksum: */
  				for(i = 0; i < 4; i++)
  					checksum += (address >> (8*i)) & 0xff;
  
  				/* make proper checksum byte: */
  				checksum = ~checksum & 0xff;
  
  				/* output one record: */
  				sprintf(record, SREC3_FORMAT, length, address, data, checksum);
  				if(write_record(record))
  					return (-1);
  			}
  			address  += reclen;  /* increment address */
  			checksum  = 0;
  			reclen    = 0;
  		}
  	}
  	while(count);
  	if(write_record(SREC3_END))	/* write the final record */
  		return (-1);
  	return(0);
  }

  static int write_record(char *buf)

  {
  	char c;
  
  	while((c = *buf++))

  		putc(c);

  
  	/* Check for the console hangup (if any different from serial) */
  
  	if (ctrlc()) {
  	    return (-1);
  	}
  	return (0);
  }

  # endif

  #endif

  #if defined(CONFIG_CMD_LOADB)

  /*
   * loadb command (load binary) included
   */

  #define XON_CHAR        17
  #define XOFF_CHAR       19
  #define START_CHAR      0x01
  #define ETX_CHAR	0x03
  #define END_CHAR        0x0D
  #define SPACE           0x20
  #define K_ESCAPE        0x23
  #define SEND_TYPE       'S'
  #define DATA_TYPE       'D'
  #define ACK_TYPE        'Y'
  #define NACK_TYPE       'N'
  #define BREAK_TYPE      'B'
  #define tochar(x) ((char) (((x) + SPACE) & 0xff))
  #define untochar(x) ((int) (((x) - SPACE) & 0xff))

  static void set_kerm_bin_mode(unsigned long *);
  static int k_recv(void);

  static ulong load_serial_bin(ulong offset);

  static char his_eol;        /* character he needs at end of packet */
  static int  his_pad_count;  /* number of pad chars he needs */
  static char his_pad_char;   /* pad chars he needs */
  static char his_quote;      /* quote chars he'll use */

  static int do_load_serial_bin(struct cmd_tbl *cmdtp, int flag, int argc,
  			      char *const argv[])

  {

  	ulong offset = 0;
  	ulong addr;
  	int load_baudrate, current_baudrate;
  	int rcode = 0;
  	char *s;

  	/* pre-set offset from CONFIG_SYS_LOAD_ADDR */
  	offset = CONFIG_SYS_LOAD_ADDR;

  
  	/* pre-set offset from $loadaddr */

  	s = env_get("loadaddr");
  	if (s)

  		offset = hextoul(s, NULL);

  
  	load_baudrate = current_baudrate = gd->baudrate;
  
  	if (argc >= 2) {

  		offset = hextoul(argv[1], NULL);

  	}
  	if (argc == 3) {

  		load_baudrate = (int)dectoul(argv[2], NULL);

  
  		/* default to current baudrate */
  		if (load_baudrate == 0)
  			load_baudrate = current_baudrate;
  	}
  
  	if (load_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ENTER ...
  ",

  			load_baudrate);
  		udelay(50000);
  		gd->baudrate = load_baudrate;

  		serial_setbrg();

  		udelay(50000);
  		for (;;) {

  			if (getchar() == '\r')

  				break;
  		}
  	}

  	if (strcmp(argv[0],"loady")==0) {

  		printf("## Ready for binary (ymodem) download "

  			"to 0x%08lX at %d bps...
  ",
  			offset,
  			load_baudrate);

  		addr = load_serial_ymodem(offset, xyzModem_ymodem);

  		if (addr == ~0) {
  			image_load_addr = 0;
  			printf("## Binary (ymodem) download aborted
  ");
  			rcode = 1;
  		} else {
  			printf("## Start Addr      = 0x%08lX
  ", addr);
  			image_load_addr = addr;
  		}

  	} else if (strcmp(argv[0],"loadx")==0) {
  		printf("## Ready for binary (xmodem) download "
  			"to 0x%08lX at %d bps...
  ",
  			offset,
  			load_baudrate);
  
  		addr = load_serial_ymodem(offset, xyzModem_xmodem);

  		if (addr == ~0) {
  			image_load_addr = 0;
  			printf("## Binary (xmodem) download aborted
  ");
  			rcode = 1;
  		} else {
  			printf("## Start Addr      = 0x%08lX
  ", addr);
  			image_load_addr = addr;
  		}

  	} else {

  		printf("## Ready for binary (kermit) download "

  			"to 0x%08lX at %d bps...
  ",
  			offset,
  			load_baudrate);

  		addr = load_serial_bin(offset);

  
  		if (addr == ~0) {

  			image_load_addr = 0;

  			printf("## Binary (kermit) download aborted
  ");

  			rcode = 1;
  		} else {

  			printf("## Start Addr      = 0x%08lX
  ", addr);

  			image_load_addr = addr;

  		}
  	}

  	if (load_baudrate != current_baudrate) {

  		printf("## Switch baudrate to %d bps and press ESC ...
  ",

  			current_baudrate);

  		udelay(50000);

  		gd->baudrate = current_baudrate;

  		serial_setbrg();
  		udelay(50000);

  		for (;;) {

  			if (getchar() == 0x1B) /* ESC */

  				break;
  		}
  	}

  	return rcode;
  }

  static ulong load_serial_bin(ulong offset)

  {
  	int size, i;

  	set_kerm_bin_mode((ulong *) offset);
  	size = k_recv();

  
  	/*
  	 * Gather any trailing characters (for instance, the ^D which
  	 * is sent by 'cu' after sending a file), and give the
  	 * box some time (100 * 1 ms)
  	 */
  	for (i=0; i<100; ++i) {

  		if (tstc()) {

  			getchar();

  		}
  		udelay(1000);
  	}

  	if (size == 0)
  		return ~0; /* Download aborted */

  	flush_cache(offset, size);

  
  	printf("## Total Size      = 0x%08x = %d Bytes
  ", size, size);

  	env_set_hex("filesize", size);

  
  	return offset;
  }

  static void send_pad(void)

  {
  	int count = his_pad_count;
  
  	while (count-- > 0)

  		putc(his_pad_char);

  }
  
  /* converts escaped kermit char to binary char */

  static char ktrans(char in)

  {
  	if ((in & 0x60) == 0x40) {
  		return (char) (in & ~0x40);
  	} else if ((in & 0x7f) == 0x3f) {
  		return (char) (in | 0x40);
  	} else
  		return in;
  }

  static int chk1(char *buffer)

  {
  	int total = 0;
  
  	while (*buffer) {
  		total += *buffer++;
  	}
  	return (int) ((total + ((total >> 6) & 0x03)) & 0x3f);
  }

  static void s1_sendpacket(char *packet)

  {

  	send_pad();

  	while (*packet) {

  		putc(*packet++);

  	}
  }
  
  static char a_b[24];

  static void send_ack(int n)

  {
  	a_b[0] = START_CHAR;

  	a_b[1] = tochar(3);
  	a_b[2] = tochar(n);

  	a_b[3] = ACK_TYPE;
  	a_b[4] = '\0';

  	a_b[4] = tochar(chk1(&a_b[1]));

  	a_b[5] = his_eol;
  	a_b[6] = '\0';

  	s1_sendpacket(a_b);

  }

  static void send_nack(int n)

  {
  	a_b[0] = START_CHAR;

  	a_b[1] = tochar(3);
  	a_b[2] = tochar(n);

  	a_b[3] = NACK_TYPE;
  	a_b[4] = '\0';

  	a_b[4] = tochar(chk1(&a_b[1]));

  	a_b[5] = his_eol;
  	a_b[6] = '\0';

  	s1_sendpacket(a_b);

  }

  static void (*os_data_init)(void);
  static void (*os_data_char)(char new_char);

  static int os_data_state, os_data_state_saved;

  static char *os_data_addr, *os_data_addr_saved;
  static char *bin_start_address;

  static void bin_data_init(void)

  {
  	os_data_state = 0;

  	os_data_addr = bin_start_address;
  }

  static void os_data_save(void)

  {
  	os_data_state_saved = os_data_state;

  	os_data_addr_saved = os_data_addr;
  }

  static void os_data_restore(void)

  {
  	os_data_state = os_data_state_saved;

  	os_data_addr = os_data_addr_saved;
  }

  static void bin_data_char(char new_char)

  {
  	switch (os_data_state) {
  	case 0:					/* data */
  		*os_data_addr++ = new_char;

  		break;
  	}
  }

  static void set_kerm_bin_mode(unsigned long *addr)

  {
  	bin_start_address = (char *) addr;
  	os_data_init = bin_data_init;
  	os_data_char = bin_data_char;
  }
  
  
  /* k_data_* simply handles the kermit escape translations */
  static int k_data_escape, k_data_escape_saved;

  static void k_data_init(void)

  {
  	k_data_escape = 0;

  	os_data_init();

  }

  static void k_data_save(void)

  {
  	k_data_escape_saved = k_data_escape;

  	os_data_save();

  }

  static void k_data_restore(void)

  {
  	k_data_escape = k_data_escape_saved;

  	os_data_restore();

  }

  static void k_data_char(char new_char)

  {
  	if (k_data_escape) {
  		/* last char was escape - translate this character */

  		os_data_char(ktrans(new_char));

  		k_data_escape = 0;
  	} else {
  		if (new_char == his_quote) {
  			/* this char is escape - remember */
  			k_data_escape = 1;
  		} else {
  			/* otherwise send this char as-is */

  			os_data_char(new_char);

  		}
  	}
  }
  
  #define SEND_DATA_SIZE  20

  static char send_parms[SEND_DATA_SIZE];
  static char *send_ptr;

  
  /* handle_send_packet interprits the protocol info and builds and
     sends an appropriate ack for what we can do */

  static void handle_send_packet(int n)

  {
  	int length = 3;
  	int bytes;
  
  	/* initialize some protocol parameters */
  	his_eol = END_CHAR;		/* default end of line character */
  	his_pad_count = 0;
  	his_pad_char = '\0';
  	his_quote = K_ESCAPE;
  
  	/* ignore last character if it filled the buffer */
  	if (send_ptr == &send_parms[SEND_DATA_SIZE - 1])
  		--send_ptr;
  	bytes = send_ptr - send_parms;	/* how many bytes we'll process */
  	do {
  		if (bytes-- <= 0)
  			break;
  		/* handle MAXL - max length */
  		/* ignore what he says - most I'll take (here) is 94 */

  		a_b[++length] = tochar(94);

  		if (bytes-- <= 0)
  			break;
  		/* handle TIME - time you should wait for my packets */
  		/* ignore what he says - don't wait for my ack longer than 1 second */

  		a_b[++length] = tochar(1);

  		if (bytes-- <= 0)
  			break;
  		/* handle NPAD - number of pad chars I need */
  		/* remember what he says - I need none */

  		his_pad_count = untochar(send_parms[2]);
  		a_b[++length] = tochar(0);

  		if (bytes-- <= 0)
  			break;
  		/* handle PADC - pad chars I need */
  		/* remember what he says - I need none */

  		his_pad_char = ktrans(send_parms[3]);

  		a_b[++length] = 0x40;	/* He should ignore this */
  		if (bytes-- <= 0)
  			break;
  		/* handle EOL - end of line he needs */
  		/* remember what he says - I need CR */

  		his_eol = untochar(send_parms[4]);
  		a_b[++length] = tochar(END_CHAR);

  		if (bytes-- <= 0)
  			break;
  		/* handle QCTL - quote control char he'll use */
  		/* remember what he says - I'll use '#' */
  		his_quote = send_parms[5];
  		a_b[++length] = '#';
  		if (bytes-- <= 0)
  			break;
  		/* handle QBIN - 8-th bit prefixing */
  		/* ignore what he says - I refuse */
  		a_b[++length] = 'N';
  		if (bytes-- <= 0)
  			break;
  		/* handle CHKT - the clock check type */
  		/* ignore what he says - I do type 1 (for now) */
  		a_b[++length] = '1';
  		if (bytes-- <= 0)
  			break;
  		/* handle REPT - the repeat prefix */
  		/* ignore what he says - I refuse (for now) */
  		a_b[++length] = 'N';
  		if (bytes-- <= 0)
  			break;
  		/* handle CAPAS - the capabilities mask */
  		/* ignore what he says - I only do long packets - I don't do windows */

  		a_b[++length] = tochar(2);	/* only long packets */
  		a_b[++length] = tochar(0);	/* no windows */
  		a_b[++length] = tochar(94);	/* large packet msb */
  		a_b[++length] = tochar(94);	/* large packet lsb */

  	} while (0);
  
  	a_b[0] = START_CHAR;

  	a_b[1] = tochar(length);
  	a_b[2] = tochar(n);

  	a_b[3] = ACK_TYPE;
  	a_b[++length] = '\0';

  	a_b[length] = tochar(chk1(&a_b[1]));

  	a_b[++length] = his_eol;
  	a_b[++length] = '\0';

  	s1_sendpacket(a_b);

  }
  
  /* k_recv receives a OS Open image file over kermit line */

  static int k_recv(void)

  {
  	char new_char;
  	char k_state, k_state_saved;
  	int sum;
  	int done;
  	int length;
  	int n, last_n;

  	int len_lo, len_hi;
  
  	/* initialize some protocol parameters */
  	his_eol = END_CHAR;		/* default end of line character */
  	his_pad_count = 0;
  	his_pad_char = '\0';
  	his_quote = K_ESCAPE;
  
  	/* initialize the k_recv and k_data state machine */
  	done = 0;
  	k_state = 0;

  	k_data_init();

  	k_state_saved = k_state;

  	k_data_save();

  	n = 0;				/* just to get rid of a warning */
  	last_n = -1;
  
  	/* expect this "type" sequence (but don't check):
  	   S: send initiate
  	   F: file header
  	   D: data (multiple)
  	   Z: end of file
  	   B: break transmission
  	 */
  
  	/* enter main loop */
  	while (!done) {
  		/* set the send packet pointer to begining of send packet parms */
  		send_ptr = send_parms;
  
  		/* With each packet, start summing the bytes starting with the length.
  		   Save the current sequence number.
  		   Note the type of the packet.
  		   If a character less than SPACE (0x20) is received - error.
  		 */
  
  #if 0
  		/* OLD CODE, Prior to checking sequence numbers */
  		/* first have all state machines save current states */
  		k_state_saved = k_state;
  		k_data_save ();
  #endif
  
  		/* get a packet */
  		/* wait for the starting character or ^C */
  		for (;;) {

  			switch (getchar()) {

  			case START_CHAR:	/* start packet */
  				goto START;
  			case ETX_CHAR:		/* ^C waiting for packet */
  				return (0);
  			default:
  				;
  			}
  		}
  START:
  		/* get length of packet */
  		sum = 0;

  		new_char = getchar();

  		if ((new_char & 0xE0) == 0)
  			goto packet_error;
  		sum += new_char & 0xff;

  		length = untochar(new_char);

  		/* get sequence number */

  		new_char = getchar();

  		if ((new_char & 0xE0) == 0)
  			goto packet_error;
  		sum += new_char & 0xff;

  		n = untochar(new_char);

  		--length;
  
  		/* NEW CODE - check sequence numbers for retried packets */
  		/* Note - this new code assumes that the sequence number is correctly
  		 * received.  Handling an invalid sequence number adds another layer
  		 * of complexity that may not be needed - yet!  At this time, I'm hoping
  		 * that I don't need to buffer the incoming data packets and can write
  		 * the data into memory in real time.
  		 */
  		if (n == last_n) {
  			/* same sequence number, restore the previous state */
  			k_state = k_state_saved;

  			k_data_restore();

  		} else {
  			/* new sequence number, checkpoint the download */
  			last_n = n;
  			k_state_saved = k_state;

  			k_data_save();

  		}
  		/* END NEW CODE */
  
  		/* get packet type */

  		new_char = getchar();

  		if ((new_char & 0xE0) == 0)
  			goto packet_error;
  		sum += new_char & 0xff;
  		k_state = new_char;
  		--length;
  		/* check for extended length */
  		if (length == -2) {
  			/* (length byte was 0, decremented twice) */
  			/* get the two length bytes */

  			new_char = getchar();

  			if ((new_char & 0xE0) == 0)
  				goto packet_error;
  			sum += new_char & 0xff;

  			len_hi = untochar(new_char);

  			new_char = getchar();

  			if ((new_char & 0xE0) == 0)
  				goto packet_error;
  			sum += new_char & 0xff;

  			len_lo = untochar(new_char);

  			length = len_hi * 95 + len_lo;
  			/* check header checksum */

  			new_char = getchar();

  			if ((new_char & 0xE0) == 0)
  				goto packet_error;

  			if (new_char != tochar((sum + ((sum >> 6) & 0x03)) & 0x3f))

  				goto packet_error;
  			sum += new_char & 0xff;
  /* --length; */ /* new length includes only data and block check to come */
  		}
  		/* bring in rest of packet */
  		while (length > 1) {

  			new_char = getchar();

  			if ((new_char & 0xE0) == 0)
  				goto packet_error;
  			sum += new_char & 0xff;
  			--length;
  			if (k_state == DATA_TYPE) {
  				/* pass on the data if this is a data packet */
  				k_data_char (new_char);
  			} else if (k_state == SEND_TYPE) {
  				/* save send pack in buffer as is */
  				*send_ptr++ = new_char;
  				/* if too much data, back off the pointer */
  				if (send_ptr >= &send_parms[SEND_DATA_SIZE])
  					--send_ptr;
  			}
  		}
  		/* get and validate checksum character */

  		new_char = getchar();

  		if ((new_char & 0xE0) == 0)
  			goto packet_error;

  		if (new_char != tochar((sum + ((sum >> 6) & 0x03)) & 0x3f))

  			goto packet_error;
  		/* get END_CHAR */

  		new_char = getchar();

  		if (new_char != END_CHAR) {
  		  packet_error:
  			/* restore state machines */
  			k_state = k_state_saved;

  			k_data_restore();

  			/* send a negative acknowledge packet in */

  			send_nack(n);

  		} else if (k_state == SEND_TYPE) {
  			/* crack the protocol parms, build an appropriate ack packet */

  			handle_send_packet(n);

  		} else {
  			/* send simple acknowledge packet in */

  			send_ack(n);

  			/* quit if end of transmission */
  			if (k_state == BREAK_TYPE)
  				done = 1;
  		}

  	}
  	return ((ulong) os_data_addr - (ulong) bin_start_address);
  }

  
  static int getcxmodem(void) {

  	if (tstc())

  		return (getchar());

  	return -1;
  }

  static ulong load_serial_ymodem(ulong offset, int mode)

  {
  	int size;

  	int err;
  	int res;
  	connection_info_t info;

  	char ymodemBuf[1024];
  	ulong store_addr = ~0;
  	ulong addr = 0;

  	size = 0;

  	info.mode = mode;

  	res = xyzModem_stream_open(&info, &err);

  	if (!res) {

  		err = 0;

  		while ((res =

  			xyzModem_stream_read(ymodemBuf, 1024, &err)) > 0) {

  			store_addr = addr + offset;
  			size += res;
  			addr += res;

  #ifdef CONFIG_MTD_NOR_FLASH

  			if (addr2info(store_addr)) {

  				int rc;

  				rc = flash_write((char *) ymodemBuf,

  						  store_addr, res);
  				if (rc != 0) {

  					xyzModem_stream_terminate(true, &getcxmodem);
  					xyzModem_stream_close(&err);
  					printf("
  ");

  					flash_perror(rc);

  					return (~0);
  				}
  			} else

  #endif

  			{

  				memcpy((char *)(store_addr), ymodemBuf,

  					res);
  			}
  
  		}

  		if (err) {
  			xyzModem_stream_terminate((err == xyzModem_cancel) ? false : true, &getcxmodem);
  			xyzModem_stream_close(&err);
  			printf("
  %s
  ", xyzModem_error(err));
  			return (~0); /* Download aborted */
  		}

  		if (IS_ENABLED(CONFIG_CMD_BOOTEFI))
  			efi_set_bootdev("Uart", "", "",
  					map_sysmem(offset, 0), size);

  	} else {

  		printf("
  %s
  ", xyzModem_error(err));
  		return (~0); /* Download aborted */

  	}

  	xyzModem_stream_terminate(false, &getcxmodem);

  	xyzModem_stream_close(&err);

  	flush_cache(offset, ALIGN(size, ARCH_DMA_MINALIGN));

  	printf("## Total Size      = 0x%08x = %d Bytes
  ", size, size);

  	env_set_hex("filesize", size);

  
  	return offset;
  }

  #endif

  
  /* -------------------------------------------------------------------- */

  #if defined(CONFIG_CMD_LOADS)

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  U_BOOT_CMD(
  	loads, 3, 0,	do_load_serial,

  	"load S-Record file over serial line",

  	"[ off ] [ baud ]
  "
  	"    - load S-Record file over serial line"

  	" with offset 'off' and baudrate 'baud'"

  );

  #else	/* ! CONFIG_SYS_LOADS_BAUD_CHANGE */

  U_BOOT_CMD(
  	loads, 2, 0,	do_load_serial,

  	"load S-Record file over serial line",

  	"[ off ]
  "

  	"    - load S-Record file over serial line with offset 'off'"

  );

  #endif	/* CONFIG_SYS_LOADS_BAUD_CHANGE */

  
  /*
   * SAVES always requires LOADS support, but not vice versa
   */

  #if defined(CONFIG_CMD_SAVES)

  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE

  U_BOOT_CMD(
  	saves, 4, 0,	do_save_serial,

  	"save S-Record file over serial line",

  	"[ off ] [size] [ baud ]
  "
  	"    - save S-Record file over serial line"

  	" with offset 'off', size 'size' and baudrate 'baud'"

  );

  #else	/* ! CONFIG_SYS_LOADS_BAUD_CHANGE */

  U_BOOT_CMD(
  	saves, 3, 0,	do_save_serial,

  	"save S-Record file over serial line",

  	"[ off ] [size]
  "

  	"    - save S-Record file over serial line with offset 'off' and size 'size'"

  );

  #endif	/* CONFIG_SYS_LOADS_BAUD_CHANGE */

  #endif	/* CONFIG_CMD_SAVES */
  #endif	/* CONFIG_CMD_LOADS */

  #if defined(CONFIG_CMD_LOADB)

  U_BOOT_CMD(
  	loadb, 3, 0,	do_load_serial_bin,

  	"load binary file over serial line (kermit mode)",

  	"[ addr [ baud ] ]
  "

  	"    - load binary file over serial line"

  	" at address 'addr' with baudrate 'baud'"

  );
  
  U_BOOT_CMD(
  	loadx, 3, 0,	do_load_serial_bin,
  	"load binary file over serial line (xmodem mode)",

  	"[ addr [ baud ] ]
  "

  	"    - load binary file over serial line"

  	" at address 'addr' with baudrate 'baud'"

  );

  U_BOOT_CMD(
  	loady, 3, 0,	do_load_serial_bin,

  	"load binary file over serial line (ymodem mode)",

  	"[ addr [ baud ] ]
  "

  	"    - load binary file over serial line"

  	" at address 'addr' with baudrate 'baud'"

  );

  #endif	/* CONFIG_CMD_LOADB */