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

#include "AT91RM9200_inc.h"
		
/*---------------------------
ARM Core Mode and Status Bits
---------------------------*/
.section start
	.text
			
#define ARM_MODE_USER   0x10
#define ARM_MODE_FIQ    0x11
#define ARM_MODE_IRQ    0x12
#define ARM_MODE_SVC    0x13
#define ARM_MODE_ABORT  0x17
#define ARM_MODE_UNDEF  0x1B
#define ARM_MODE_SYS    0x1F

#define I_BIT           0x80
#define F_BIT           0x40
#define T_BIT           0x20

/*----------------------------------------------------------------------------
 Area Definition
----------------
 Must be defined as function to put first in the code as it must be mapped
 at offset 0 of the flash EBI_CSR0, ie. at address 0 before remap.
_---------------------------------------------------------------------------*/

  .align  4
	.globl _start
_start:

/*----------------------------------------------------------------------------
 Exception vectors ( before Remap )
------------------------------------
 These vectors are read at address 0.
 They absolutely requires to be in relative addresssing mode in order to
 guarantee a valid jump. For the moment, all are just looping (what may be
 dangerous in a final system). If an exception occurs before remap, this
 would result in an infinite loop.
----------------------------------------------------------------------------*/
                b           reset			       	/* reset */
                b           undefvec        	/* Undefined Instruction */
                b           swivec          	/* Software Interrupt */
                b           pabtvec         	/* Prefetch Abort */
                b           dabtvec         	/* Data Abort */
                b           rsvdvec         	/* reserved */
                b           aicvec				    /* IRQ : read the AIC */
                b           fiqvec          	/* FIQ */

undefvec:
swivec:
pabtvec:
dabtvec:
rsvdvec:
aicvec:
fiqvec:
	b	undefvec

reset:

#define MEMEND 0x00004000

/* ----------------------------
 Setup the stack for each mode
---------------------------- */

#define IRQ_STACK_SIZE  0x10
#define FIQ_STACK_SIZE  0x04
#define ABT_STACK_SIZE  0x04
#define UND_STACK_SIZE  0x04
#define SVC_STACK_SIZE  0x10
#define USER_STACK_SIZE 0x400
	
                ldr     r0,= MEMEND

/*- Set up Supervisor Mode and set Supervisor Mode Stack*/
                msr     CPSR_c, #ARM_MODE_SVC | I_BIT | F_BIT
                mov     r13, r0                     /* Init stack Undef*/
                sub     r0, r0, #SVC_STACK_SIZE

/*- Set up Interrupt Mode and set IRQ Mode Stack*/
                msr     CPSR_c, #ARM_MODE_IRQ | I_BIT | F_BIT
                mov     r13, r0                     /* Init stack IRQ*/
                sub     r0, r0, #IRQ_STACK_SIZE

/*- Set up Fast Interrupt Mode and set FIQ Mode Stack*/
                msr     CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT
                mov     r13, r0                     /* Init stack FIQ*/
                sub     r0, r0, #FIQ_STACK_SIZE

/*- Set up Abort Mode and set Abort Mode Stack*/
                msr     CPSR_c, #ARM_MODE_ABORT | I_BIT | F_BIT
                mov     r13, r0                     /* Init stack Abort*/
                sub     r0, r0, #ABT_STACK_SIZE

/*- Set up Undefined Instruction Mode and set Undef Mode Stack*/
                msr     CPSR_c, #ARM_MODE_UNDEF | I_BIT | F_BIT
                mov     r13, r0                     /* Init stack Undef*/
                sub     r0, r0, #UND_STACK_SIZE

/*- Set up user Mode and set System Mode Stack*/
                msr     CPSR_c, #ARM_MODE_SYS | I_BIT | F_BIT
                bic     r0, r0, #3                  /* Insure word alignement */
               	mov     sp, r0                      /* Init stack System */


		ldr       r0, = AT91F_LowLevelInit
		mov       lr, pc
		bx        r0

/*----------------------------------------
 Read/modify/write CP15 control register
----------------------------------------*/
		mrc     p15, 0, r0, c1, c0,0  /* read cp15 control registre (cp15 r1) in r0 */
		ldr     r3,= 0xC0000080      /* Reset bit :Little Endian end fast bus mode */
		ldr     r4,= 0xC0001000      /* Set bit :Asynchronous clock mode, Not Fast Bus, I-Cache enable */
		bic     r0, r0, r3
		orr     r0, r0, r4
		mcr     p15, 0, r0, c1, c0,0 /* write r0 in cp15 control registre (cp15 r1) */

/* Enable interrupts */
		msr     CPSR_c, #ARM_MODE_SYS | F_BIT

/*------------------------------------------------------------------------------
- Branch on C code Main function (with interworking)
----------------------------------------------------
- Branch must be performed by an interworking call as either an ARM or Thumb
- _start function must be supported. This makes the code not position-
- independent. A Branch with link would generate errors
----------------------------------------------------------------------------*/
	
/*- Branch to _start by interworking*/
		ldr     r4, = main
	        mov     lr, pc
	        bx      r4
	
/*-----------------------------------------------------------------------------
- Loop for ever
---------------
- End of application. Normally, never occur.
- Could jump on Software Reset ( B 0x0 ).
------------------------------------------------------------------------------*/
End:
	        b       End