target/linux/at91/image/dfboot/src/cstartup_ram.S

   1 #include "AT91RM9200_inc.h"
   2
   3 /*---------------------------
   4 ARM Core Mode and Status Bits
   5 ---------------------------*/
   6 .section start
   7         .text
   8
   9 #define ARM_MODE_USER   0x10
  10 #define ARM_MODE_FIQ    0x11
  11 #define ARM_MODE_IRQ    0x12
  12 #define ARM_MODE_SVC    0x13
  13 #define ARM_MODE_ABORT  0x17
  14 #define ARM_MODE_UNDEF  0x1B
  15 #define ARM_MODE_SYS    0x1F
  16
  17 #define I_BIT           0x80
  18 #define F_BIT           0x40
  19 #define T_BIT           0x20
  20
  21 /*----------------------------------------------------------------------------
  22  Area Definition
  23 ----------------
  24  Must be defined as function to put first in the code as it must be mapped
  25  at offset 0 of the flash EBI_CSR0, ie. at address 0 before remap.
  26 _---------------------------------------------------------------------------*/
  27
  28   .align  4
  29         .globl _start
  30 _start:
  31
  32 /*----------------------------------------------------------------------------
  33  Exception vectors ( before Remap )
  34 ------------------------------------
  35  These vectors are read at address 0.
  36  They absolutely requires to be in relative addresssing mode in order to
  37  guarantee a valid jump. For the moment, all are just looping (what may be
  38  dangerous in a final system). If an exception occurs before remap, this
  39  would result in an infinite loop.
  40 ----------------------------------------------------------------------------*/
  41                 b           reset                               /* reset */
  42                 b           undefvec            /* Undefined Instruction */
  43                 b           swivec              /* Software Interrupt */
  44                 b           pabtvec             /* Prefetch Abort */
  45                 b           dabtvec             /* Data Abort */
  46                 b           rsvdvec             /* reserved */
  47                 b           aicvec                                  /* IRQ : read the AIC */
  48                 b           fiqvec              /* FIQ */
  49
  50 undefvec:
  51 swivec:
  52 pabtvec:
  53 dabtvec:
  54 rsvdvec:
  55 aicvec:
  56 fiqvec:
  57         b       undefvec
  58
  59 reset:
  60
  61 #define MEMEND 0x00004000
  62
  63 /* ----------------------------
  64  Setup the stack for each mode
  65 ---------------------------- */
  66
  67 #define IRQ_STACK_SIZE  0x10
  68 #define FIQ_STACK_SIZE  0x04
  69 #define ABT_STACK_SIZE  0x04
  70 #define UND_STACK_SIZE  0x04
  71 #define SVC_STACK_SIZE  0x10
  72 #define USER_STACK_SIZE 0x400
  73
  74                 ldr     r0,= MEMEND
  75
  76 /*- Set up Supervisor Mode and set Supervisor Mode Stack*/
  77                 msr     CPSR_c, #ARM_MODE_SVC | I_BIT | F_BIT
  78                 mov     r13, r0                     /* Init stack Undef*/
  79                 sub     r0, r0, #SVC_STACK_SIZE
  80
  81 /*- Set up Interrupt Mode and set IRQ Mode Stack*/
  82                 msr     CPSR_c, #ARM_MODE_IRQ | I_BIT | F_BIT
  83                 mov     r13, r0                     /* Init stack IRQ*/
  84                 sub     r0, r0, #IRQ_STACK_SIZE
  85
  86 /*- Set up Fast Interrupt Mode and set FIQ Mode Stack*/
  87                 msr     CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT
  88                 mov     r13, r0                     /* Init stack FIQ*/
  89                 sub     r0, r0, #FIQ_STACK_SIZE
  90
  91 /*- Set up Abort Mode and set Abort Mode Stack*/
  92                 msr     CPSR_c, #ARM_MODE_ABORT | I_BIT | F_BIT
  93                 mov     r13, r0                     /* Init stack Abort*/
  94                 sub     r0, r0, #ABT_STACK_SIZE
  95
  96 /*- Set up Undefined Instruction Mode and set Undef Mode Stack*/
  97                 msr     CPSR_c, #ARM_MODE_UNDEF | I_BIT | F_BIT
  98                 mov     r13, r0                     /* Init stack Undef*/
  99                 sub     r0, r0, #UND_STACK_SIZE
 100
 101 /*- Set up user Mode and set System Mode Stack*/
 102                 msr     CPSR_c, #ARM_MODE_SYS | I_BIT | F_BIT
 103                 bic     r0, r0, #3                  /* Insure word alignement */
 104                 mov     sp, r0                      /* Init stack System */
 105
 106
 107                 ldr       r0, = AT91F_LowLevelInit
 108                 mov       lr, pc
 109                 bx        r0
 110
 111 /*----------------------------------------
 112  Read/modify/write CP15 control register
 113 ----------------------------------------*/
 114                 mrc     p15, 0, r0, c1, c0,0  /* read cp15 control registre (cp15 r1) in r0 */
 115                 ldr     r3,= 0xC0000080      /* Reset bit :Little Endian end fast bus mode */
 116                 ldr     r4,= 0xC0001000      /* Set bit :Asynchronous clock mode, Not Fast Bus, I-Cache enable */
 117                 bic     r0, r0, r3
 118                 orr     r0, r0, r4
 119                 mcr     p15, 0, r0, c1, c0,0 /* write r0 in cp15 control registre (cp15 r1) */
 120
 121 /* Enable interrupts */
 122                 msr     CPSR_c, #ARM_MODE_SYS | F_BIT
 123
 124 /*------------------------------------------------------------------------------
 125 - Branch on C code Main function (with interworking)
 126 ----------------------------------------------------
 127 - Branch must be performed by an interworking call as either an ARM or Thumb
 128 - _start function must be supported. This makes the code not position-
 129 - independent. A Branch with link would generate errors
 130 ----------------------------------------------------------------------------*/
 131
 132 /*- Branch to _start by interworking*/
 133                 ldr     r4, = main
 134                 mov     lr, pc
 135                 bx      r4
 136
 137 /*-----------------------------------------------------------------------------
 138 - Loop for ever
 139 ---------------
 140 - End of application. Normally, never occur.
 141 - Could jump on Software Reset ( B 0x0 ).
 142 ------------------------------------------------------------------------------*/
 143 End:
 144                 b       End