OpenWrt – Rev 4
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#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