/* $Id: head.S,v 1.8 2001/10/03 17:15:15 bjornw Exp $
 * 
 * Rescue code, made to reside at the beginning of the
 * flash-memory. when it starts, it checks a partition
 * table at the first sector after the rescue sector.
 * the partition table was generated by the product builder
 * script and contains offsets, lengths, types and checksums
 * for each partition that this code should check.
 *
 * If any of the checksums fail, we assume the flash is so
 * corrupt that we cant use it to boot into the ftp flash
 * loader, and instead we initialize the serial port to
 * receive a flash-loader and new flash image. we dont include
 * any flash code here, but just accept a certain amount of
 * bytes from the serial port and jump into it. the downloaded
 * code is put in the cache.
 *
 * The partitiontable is designed so that it is transparent to
 * code execution - it has a relative branch opcode in the
 * beginning that jumps over it. each entry contains extra
 * data so we can add stuff later.
 *
 * Partition table format:
 *
 *     Code transparency:
 * 
 *     2 bytes    [opcode 'nop']
 *     2 bytes    [opcode 'di']
 *     4 bytes    [opcode 'ba <offset>', 8-bit or 16-bit version]
 *     2 bytes    [opcode 'nop', delay slot]
 *
 *     Table validation (at +10):	
 * 
 *     2 bytes    [magic/version word for partitiontable - 0xef, 0xbe]
 *     2 bytes    [length of all entries plus the end marker]
 *     4 bytes    [checksum for the partitiontable itself]
 *
 *     Entries, each with the following format, last has offset -1:	
 *    
 *        4 bytes    [offset in bytes, from start of flash]
 *        4 bytes    [length in bytes of partition]
 *        4 bytes    [checksum, simple longword sum]
 *        2 bytes    [partition type]
 *        2 bytes    [flags, only bit 0 used, ro/rw = 1/0]
 *        16 bytes   [reserved for future use]
 *
 *     End marker
 *
 *        4 bytes    [-1]
 * 
 *	 10 bytes    [0, padding]
 * 
 * Bit 0 in flags signifies RW or RO. The rescue code only bothers
 * to check the checksum for RO partitions, since the others will
 * change its data without updating the checksums. A 1 in bit 0
 * means RO, 0 means RW. That way, it is possible to set a partition
 * in RO mode initially, and later mark it as RW, since you can always
 * write 0's to the flash.
 *
 * During the wait for serial input, the status LED will flash so the
 * user knows something went wrong.
 * 
 * Copyright (C) 1999,2001 Axis Communications AB
 */

#include <linux/config.h>
#define ASSEMBLER_MACROS_ONLY
#include <asm/sv_addr_ag.h>

	;; The partitiontable is looked for at the first sector after the boot
	;; sector. Sector size is 65536 bytes in all flashes we use.
		
#define PTABLE_START CONFIG_ETRAX_PTABLE_SECTOR
#define PTABLE_MAGIC 0xbeef

	;; The normal Etrax100 on-chip boot ROM does serial boot at 0x380000f0.
	;; That is not where we put our downloaded serial boot-code. The length is
	;; enough for downloading code that loads the rest of itself (after
	;; having setup the DRAM etc). It is the same length as the on-chip
	;; ROM loads, so the same host loader can be used to load a rescued
	;; product as well as one booted through the Etrax serial boot code.
		
#define CODE_START 0x40000000
#define CODE_LENGTH 784

#ifdef CONFIG_ETRAX_RESCUE_SER0
#define SERXOFF R_SERIAL0_XOFF
#define SERBAUD R_SERIAL0_BAUD
#define SERRECC R_SERIAL0_REC_CTRL
#define SERRDAT R_SERIAL0_REC_DATA
#define SERSTAT R_SERIAL0_STATUS
#endif
#ifdef CONFIG_ETRAX_RESCUE_SER1
#define SERXOFF R_SERIAL1_XOFF
#define SERBAUD R_SERIAL1_BAUD
#define SERRECC R_SERIAL1_REC_CTRL
#define SERRDAT R_SERIAL1_REC_DATA
#define SERSTAT R_SERIAL1_STATUS
#endif
#ifdef CONFIG_ETRAX_RESCUE_SER2
#define SERXOFF R_SERIAL2_XOFF
#define SERBAUD R_SERIAL2_BAUD
#define SERRECC R_SERIAL2_REC_CTRL
#define SERRDAT R_SERIAL2_REC_DATA
#define SERSTAT R_SERIAL2_STATUS
#endif	
#ifdef CONFIG_ETRAX_RESCUE_SER3
#define SERXOFF R_SERIAL3_XOFF
#define SERBAUD R_SERIAL3_BAUD
#define SERRECC R_SERIAL3_REC_CTRL
#define SERRDAT R_SERIAL3_REC_DATA
#define SERSTAT R_SERIAL3_STATUS
#endif

#define NOP_DI 0xf025050f
#define RAM_INIT_MAGIC 0x56902387
		
	.text
	
	;; This is the entry point of the rescue code
	;; 0x80000000 if loaded in flash (as it should be)
	;; since etrax actually starts at address 2 when booting from flash, we
	;; put a nop (2 bytes) here first so we dont accidentally skip the di
	
	nop	
	di

	jump	in_cache	; enter cached area instead
in_cache:	

	;; first put a jump test to give a possibility of upgrading the rescue code
	;; without erasing/reflashing the sector. we put a longword of -1 here and if
	;; its not -1, we jump using the value as jump target. since we can always
	;; change 1's to 0's without erasing the sector, it is possible to add new
	;; code after this and altering the jumptarget in an upgrade.

jtcd:	move.d	[jumptarget], $r0
	cmp.d	0xffffffff, $r0
	beq	no_newjump
	nop
	
	jump	[$r0]

jumptarget:	
	.dword	0xffffffff	; can be overwritten later to insert new code
	
no_newjump:	
	;; We need to setup the bus registers before we start using the DRAM
#include "../../lib/dram_init.S"

	;; we now should go through the checksum-table and check the listed
	;; partitions for errors.
	
	move.d	PTABLE_START, $r3
	move.d	[$r3], $r0
	cmp.d	NOP_DI, $r0	; make sure the nop/di is there...
	bne	do_rescue
	nop
	
	;; skip the code transparency block (10 bytes).

	addq	10, $r3
	
	;; check for correct magic
	
	move.w	[$r3+], $r0
	cmp.w	PTABLE_MAGIC, $r0
	bne	do_rescue	; didn't recognize - trig rescue
	nop

	;; check for correct ptable checksum

	movu.w	[$r3+], $r2	; ptable length
	move.d	$r2, $r8	; save for later, length of total ptable
	addq	28, $r8		; account for the rest
	move.d	[$r3+], $r4	; ptable checksum
	move.d	$r3, $r1
	jsr	checksum	; r1 source, r2 length, returns in r0

	cmp.d	$r0, $r4
	bne	do_rescue	; didn't match - trig rescue
	nop
	
	;; ptable is ok. validate each entry.

	moveq	-1, $r7
	
ploop:	move.d	[$r3+], $r1	; partition offset (from ptable start)
	bne	notfirst	; check if its the partition containing ptable
	nop			; yes..
	move.d	$r8, $r1	; for its checksum check, skip the ptable
	move.d	[$r3+], $r2	; partition length
	sub.d	$r8, $r2	; minus the ptable length
	ba	bosse
	nop
notfirst:	
	cmp.d	-1, $r1		; the end of the ptable ?
	beq	flash_ok	;   if so, the flash is validated
	move.d	[$r3+], $r2	; partition length
bosse:	move.d	[$r3+], $r5	; checksum
	move.d	[$r3+], $r4	; type and flags
	addq	16, $r3		; skip the reserved bytes
	btstq	16, $r4		; check ro flag
	bpl	ploop		;   rw partition, skip validation
	nop
	btstq	17, $r4		; check bootable flag
	bpl	1f
	nop
	move.d	$r1, $r7	; remember boot partition offset
1:	

	add.d	PTABLE_START, $r1
	
	jsr	checksum	; checksum the partition
	
	cmp.d	$r0, $r5
	beq	ploop		; checksums matched, go to next entry
	nop

	;; otherwise fall through to the rescue code.
	
do_rescue:
	;; setup port PA and PB default initial directions and data
	;; (so we can flash LEDs, and so that DTR and others are set)
	
	move.b	CONFIG_ETRAX_DEF_R_PORT_PA_DIR, $r0
	move.b	$r0, [R_PORT_PA_DIR]
	move.b	CONFIG_ETRAX_DEF_R_PORT_PA_DATA, $r0
	move.b	$r0, [R_PORT_PA_DATA]
	
	move.b	CONFIG_ETRAX_DEF_R_PORT_PB_DIR, $r0
	move.b	$r0, [R_PORT_PB_DIR]
	move.b	CONFIG_ETRAX_DEF_R_PORT_PB_DATA, $r0
	move.b	$r0, [R_PORT_PB_DATA]

	;; setup the serial port at 115200 baud
	
	moveq	0, $r0
	move.d	$r0, [SERXOFF] 

	move.b	0x99, $r0
	move.b	$r0, [SERBAUD]		; 115.2kbaud for both transmit and receive

	move.b	0x40, $r0		; rec enable
	move.b	$r0, [SERRECC] 

	moveq	0, $r1		; "timer" to clock out a LED red flash
	move.d	CODE_START, $r3	; destination counter
	movu.w	CODE_LENGTH, $r4; length
	
wait_ser:
	addq	1, $r1
#ifndef CONFIG_ETRAX_NO_LEDS
#ifdef CONFIG_ETRAX_PA_LEDS
	move.b	CONFIG_ETRAX_DEF_R_PORT_PA_DATA, $r2
#endif
#ifdef CONFIG_ETRAX_PB_LEDS
	move.b	CONFIG_ETRAX_DEF_R_PORT_PB_DATA, $r2
#endif
	move.d	(1 << CONFIG_ETRAX_LED1R) | (1 << CONFIG_ETRAX_LED2R), $r0
	btstq	16, $r1
	bpl	1f
	nop
	or.d	$r0, $r2	; set bit
	ba	2f
	nop
1:	not	$r0		; clear bit
	and.d	$r0, $r2
2:	
#ifdef CONFIG_ETRAX_PA_LEDS
	move.b	$r2, [R_PORT_PA_DATA]	
#endif	
#ifdef CONFIG_ETRAX_PB_LEDS
	move.b	$r2, [R_PORT_PB_DATA]	
#endif
#ifdef CONFIG_ETRAX_90000000_LEDS
	move.b	$r2, [0x90000000]
#endif
#endif
	
	;; check if we got something on the serial port
	
	move.b	[SERSTAT], $r0
	btstq	0, $r0		; data_avail
	bpl	wait_ser
	nop

	;; got something - copy the byte and loop

	move.b	[SERRDAT], $r0
	move.b	$r0, [$r3+]
	
	subq	1, $r4		; decrease length
	bne	wait_ser
	nop

	;; jump into downloaded code

	move.d	RAM_INIT_MAGIC, $r8	; Tell next product that DRAM is initialized
	jump	CODE_START

flash_ok:
	;; check r7, which contains either -1 or the partition to boot from

	cmp.d	-1, $r7
	bne	1f
	nop
	move.d	PTABLE_START, $r7; otherwise use the ptable start
1:
	move.d	RAM_INIT_MAGIC, $r8	; Tell next product that DRAM is initialized
	jump	$r7		; boot!


	;; Helper subroutines

	;; Will checksum by simple addition
	;; r1 - source
	;; r2 - length in bytes
	;; result will be in r0
checksum:
	moveq	0, $r0
1:	addu.b	[$r1+], $r0
	subq	1, $r2
	bne	1b
	nop
	ret
	nop