target/linux/ar71xx/image/lzma-loader/src/head.S

   1 /*
   2  * LZMA compressed kernel loader for Atheros AR7XXX/AR9XXX based boards
   3  *
   4  * Copyright (C) 2011 Gabor Juhos <juhosg@openwrt.org>
   5  *
   6  * Some parts of this code was based on the OpenWrt specific lzma-loader
   7  * for the BCM47xx and ADM5120 based boards:
   8  *      Copyright (C) 2004 Manuel Novoa III (mjn3@codepoet.org)
   9  *      Copyright (C) 2005 by Oleg I. Vdovikin <oleg@cs.msu.su>
  10  *
  11  * This program is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU General Public License version 2 as published
  13  * by the Free Software Foundation.
  14  */
  15
  16 #include <asm/asm.h>
  17 #include <asm/regdef.h>
  18 #include "cp0regdef.h"
  19 #include "cacheops.h"
  20 #include "config.h"
  21
  22 #define KSEG0           0x80000000
  23
  24         .macro  ehb
  25         sll     zero, 3
  26         .endm
  27
  28         .text
  29
  30 LEAF(startup)
  31         .set noreorder
  32         .set mips32
  33
  34         mtc0    zero, CP0_WATCHLO       # clear watch registers
  35         mtc0    zero, CP0_WATCHHI
  36         mtc0    zero, CP0_CAUSE         # clear before writing status register
  37
  38         mfc0    t0, CP0_STATUS
  39         li      t1, 0x1000001f
  40         or      t0, t1
  41         xori    t0, 0x1f
  42         mtc0    t0, CP0_STATUS
  43         ehb
  44
  45         mtc0    zero, CP0_COUNT
  46         mtc0    zero, CP0_COMPARE
  47         ehb
  48
  49         la      t0, __reloc_label       # get linked address of label
  50         bal     __reloc_label           # branch and link to label to
  51         nop                             # get actual address
  52 __reloc_label:
  53         subu    t0, ra, t0              # get reloc_delta
  54
  55         beqz    t0, __reloc_done         # if delta is 0 we are in the right place
  56         nop
  57
  58         /* Copy our code to the right place */
  59         la      t1, _code_start         # get linked address of _code_start
  60         la      t2, _code_end           # get linked address of _code_end
  61         addu    t0, t0, t1              # calculate actual address of _code_start
  62
  63 __reloc_copy:
  64         lw      t3, 0(t0)
  65         sw      t3, 0(t1)
  66         add     t1, 4
  67         blt     t1, t2, __reloc_copy
  68         add     t0, 4
  69
  70         /* flush cache */
  71         la      t0, _code_start
  72         la      t1, _code_end
  73
  74         li      t2, ~(CONFIG_CACHELINE_SIZE - 1)
  75         and     t0, t2
  76         and     t1, t2
  77         li      t2, CONFIG_CACHELINE_SIZE
  78
  79         b       __flush_check
  80         nop
  81
  82 __flush_line:
  83         cache   Hit_Writeback_Inv_D, 0(t0)
  84         cache   Hit_Invalidate_I, 0(t0)
  85         add     t0, t2
  86
  87 __flush_check:
  88         bne     t0, t1, __flush_line
  89         nop
  90
  91         sync
  92
  93 __reloc_done:
  94
  95         /* clear bss */
  96         la      t0, _bss_start
  97         la      t1, _bss_end
  98         b       __bss_check
  99         nop
 100
 101 __bss_fill:
 102         sw      zero, 0(t0)
 103         addi    t0, 4
 104
 105 __bss_check:
 106         bne     t0, t1, __bss_fill
 107         nop
 108
 109         /* Setup new "C" stack */
 110         la      sp, _stack
 111
 112         /* reserve stack space for a0-a3 registers */
 113         subu    sp, 16
 114
 115         /* jump to the decompressor routine */
 116         la      t0, loader_main
 117         jr      t0
 118         nop
 119
 120         .set reorder
 121 END(startup)