text: // 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 <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)simple_strtoul(argv[2], NULL, 10);
  
  		/* 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 ...\n",
  			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 ...\n");
  
  	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\n");
  		rcode = 1;
  	} else {
  		printf("## Start Addr      = 0x%08lX\n", 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 ...\n",
  			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)
  {
  	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;
  
  	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
  		    {
  			memcpy((char *)(store_addr), binbuf, 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("\n"
  			    "## First Load Addr = 0x%08lX\n"
  			    "## Last  Load Addr = 0x%08lX\n"
  			    "## Total Size      = 0x%08lX = %ld Bytes\n",
  			    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 '\n':
  			*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 = simple_strtoul(argv[1], NULL, 16);
  	}
  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE
  	if (argc >= 3) {
  		size = simple_strtoul(argv[2], NULL, 16);
  	}
  	if (argc == 4) {
  		save_baudrate = (int)simple_strtoul(argv[3], NULL, 10);
  
  		/* 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 ...\n",
  			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 = simple_strtoul(argv[2], NULL, 16);
  	}
  #endif	/* CONFIG_SYS_LOADS_BAUD_CHANGE */
  
  	printf("## Ready for S-Record upload, press ENTER to proceed ...\n");
  	for (;;) {
  		if (getchar() == '\r')
  			break;
  	}
  	if (save_serial(offset, size)) {
  		printf("## S-Record upload aborted\n");
  	} else {
  		printf("## S-Record upload complete\n");
  	}
  #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE
  	if (save_baudrate != current_baudrate) {
  		printf("## Switch baudrate to %d bps and press ESC ...\n",
  			(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\n"
  #define SREC3_FORMAT			"S3%02X%08lX%s%02X\n"
  #define SREC3_END				"S70500000000FA\n"
  #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 = simple_strtoul(s, NULL, 16);
  
  	load_baudrate = current_baudrate = gd->baudrate;
  
  	if (argc >= 2) {
  		offset = simple_strtoul(argv[1], NULL, 16);
  	}
  	if (argc == 3) {
  		load_baudrate = (int)simple_strtoul(argv[2], NULL, 10);
  
  		/* 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 ...\n",
  			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...\n",
  			offset,
  			load_baudrate);
  
  		addr = load_serial_ymodem(offset, xyzModem_ymodem);
  
  	} else if (strcmp(argv[0],"loadx")==0) {
  		printf("## Ready for binary (xmodem) download "
  			"to 0x%08lX at %d bps...\n",
  			offset,
  			load_baudrate);
  
  		addr = load_serial_ymodem(offset, xyzModem_xmodem);
  
  	} else {
  
  		printf("## Ready for binary (kermit) download "
  			"to 0x%08lX at %d bps...\n",
  			offset,
  			load_baudrate);
  		addr = load_serial_bin(offset);
  
  		if (addr == ~0) {
  			image_load_addr = 0;
  			printf("## Binary (kermit) download aborted\n");
  			rcode = 1;
  		} else {
  			printf("## Start Addr      = 0x%08lX\n", addr);
  			image_load_addr = addr;
  		}
  	}
  	if (load_baudrate != current_baudrate) {
  		printf("## Switch baudrate to %d bps and press ESC ...\n",
  			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);
  	}
  
  	flush_cache(offset, size);
  
  	printf("## Total Size      = 0x%08x = %d Bytes\n", 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) {
  
  		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) {
  					flash_perror(rc);
  					return (~0);
  				}
  			} else
  #endif
  			{
  				memcpy((char *)(store_addr), ymodemBuf,
  					res);
  			}
  
  		}
  		if (IS_ENABLED(CONFIG_CMD_BOOTEFI))
  			efi_set_bootdev("Uart", "", "",
  					map_sysmem(offset, 0), size);
  
  	} else {
  		printf("%s\n", xyzModem_error(err));
  	}
  
  	xyzModem_stream_close(&err);
  	xyzModem_stream_terminate(false, &getcxmodem);
  
  
  	flush_cache(offset, ALIGN(size, ARCH_DMA_MINALIGN));
  
  	printf("## Total Size      = 0x%08x = %d Bytes\n", 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 ]\n"
  	"    - 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 ]\n"
  	"    - 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 ]\n"
  	"    - 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]\n"
  	"    - 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 ] ]\n"
  	"    - 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 ] ]\n"
  	"    - 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 ] ]\n"
  	"    - load binary file over serial line"
  	" at address 'addr' with baudrate 'baud'"
  );
  
  #endif	/* CONFIG_CMD_LOADB */
  