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/*
 * 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 their 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, 2000, 2001, 2002, 2003 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
        ;; it is 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:
#ifdef CONFIG_ETRAX_ETHERNET            
        ;; Start MII clock to make sure it is running when tranceiver is reset
        move.d 0x3, $r0    ; enable = on, phy = mii_clk
        move.d $r0, [R_NETWORK_GEN_CONFIG]
#endif

        ;; 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]

        ;; 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 it is 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 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