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sam7fc/at91_init0.s

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ArmAsm
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/***************************************************************************
* Copyright (C) 01/2008 by Olaf Rempel *
* razzor@kopf-tisch.de *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; version 2 of the License *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program; if not, write to the *
* Free Software Foundation, Inc., *
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
***************************************************************************/
.equ AIC_IVR, (256)
.equ AIC_FVR, (260)
.equ AIC_EOICR, (304)
.equ AT91C_BASE_AIC, (0xFFFFF000)
.equ IRQ_Stack_Size, (3 * 8 * 4)
.equ FIQ_Stack_Size, (3 * 8 * 4)
.equ ABT_Stack_Size, 192
.equ ARM_MODE_FIQ, 0x11
.equ ARM_MODE_IRQ, 0x12
.equ ARM_MODE_SVC, 0x13
.equ ARM_MODE_ABT, 0x17
.equ I_BIT, 0x80
.equ F_BIT, 0x40
.section .text
.global _start
.func _start
_start: ldr pc, [pc, #24] /* 0x00 Reset handler */
undefvec: ldr pc, [pc, #24] /* 0x04 Undefined Instruction */
swivec: ldr pc, [pc, #24] /* 0x08 Software Interrupt */
pabtvec: ldr pc, [pc, #24] /* 0x0C Prefetch Abort */
dabtvec: ldr pc, [pc, #24] /* 0x10 Data Abort */
rsvdvec: ldr pc, [pc, #24] /* 0x14 reserved */
irqvec: ldr pc, [pc, #24] /* 0x18 IRQ */
fiqvec: ldr pc, [pc, #24] /* 0x1c FIQ */
/* 0x80000000 will result in Prefetch Abort */
.word InitReset
.word 0x80000000
.word 0x80000000
.word ABT_Handler_Entry
.word ABT_Handler_Entry
.word 0x80000000
.word IRQ_Handler_Entry
.word FIQ_Handler_Entry
.endfunc
.global InitReset
.func InitReset
InitReset:
.extern at91_init1
/* Call Low level init function */
ldr sp,=__stack_top__
ldr r0,=at91_init1
mov lr, pc
bx r0
mov r0, sp
/* Setup FIQ Mode Stack */
msr CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT
mov sp, r0
sub r0, r0, #FIQ_Stack_Size
/* store AIC Base in ARM_MODE_FIQ:r8 for faster access */
ldr r8, =AT91C_BASE_AIC
/* Setup IRQ Mode Stack */
msr CPSR_c, #ARM_MODE_IRQ | I_BIT | F_BIT
mov sp, r0
sub r0, r0, #IRQ_Stack_Size
/* Setup Abort Mode Stack */
msr CPSR_c, #ARM_MODE_ABT | I_BIT | F_BIT
mov sp, r0
sub r0, r0, #ABT_Stack_Size
/* Setup Supervisor Mode Stack (IRQ & NMI enabled) */
msr CPSR_c, #ARM_MODE_SVC
mov sp, r0
/* Relocate .data section */
ldr r1, =__text_end__
ldr r2, =__data_start__
ldr r3, =__data_end__
LoopRel: cmp r2, r3
ldrlo r0, [r1], #4
strlo r0, [r2], #4
blo LoopRel
/* Clear .bss section */
mov r0, #0
ldr r1, =__bss_start__
ldr r2, =__bss_end__
LoopZI: cmp r1, r2
strlo r0, [r1], #4
BLO LoopZI
/* Start main() */
ldr lr,=exit
ldr r0,=main
bx r0
.endfunc
.global exit
.func exit
/* exit dummy for newlib */
exit: b .
.endfunc
.global ABT_Handler_Entry
.func ABT_Handler_Entry
ABT_Handler_Entry:
/* disable interrupts (F_BIT not set on entry) */
msr CPSR_c, #ARM_MODE_ABT | I_BIT | F_BIT
/* store all registers */
stmfd sp!, { r0-r12 }
/* saved cpsr (from aborted mode) */
mrs r0, SPSR
/* address of abort (pc) */
mov r3, lr
/* enter previous mode and get lr(r14), sp(r13) */
/* TODO: interrupts might be enabled? */
/* TODO: thumb mode enabled? */
msr CPSR_c, r0
mov r1, sp
mov r2, lr
/* return to abort mode */
msr CPSR_c, #ARM_MODE_ABT | I_BIT | F_BIT
/* store remaining registers (r1-r3 == r13-r15) */
stmfd sp!, { r1-r3 }
mov r1, sp
/* execute C Handler (cpsr, registers) */
ldr r5,=at91_abt_handler
mov lr, pc
bx r5
b .
.endfunc
.global FIQ_Handler_Entry
.func FIQ_Handler_Entry
FIQ_Handler_Entry:
/* Save r0 to ARM_MODE_FIQ:r9 */
mov r9,r0
/* get FIQ Vector from AIC and thus clear FIQ */
ldr r0 , [r8, #AIC_FVR]
/* Switch to ARM_MODE_SVC and save registers there */
msr CPSR_c,#ARM_MODE_SVC | I_BIT | F_BIT
stmfd sp!, { r1-r3, r12, lr}
/* execute FIQ in SVC_MODE */
mov r14, pc
bx r0
/* restore registers and switch back to ARM_MODE_FIQ */
ldmia sp!, { r1-r3, r12, lr}
msr CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT
/* restore the ARM_MODE_SVC:r0 */
mov r0,r9
/* restore PC using the LR_fiq directly */
subs pc,lr,#4
.endfunc
.global IRQ_Handler_Entry
.func IRQ_Handler_Entry
IRQ_Handler_Entry:
/*- Manage Exception Entry */
/*- Adjust and save LR_irq in IRQ stack */
sub lr, lr, #4
stmfd sp!, {lr}
/*- Save SPSR need to be saved for nested interrupt */
mrs r14, SPSR
stmfd sp!, {r14}
/*- Save and r0 in IRQ stack */
stmfd sp!, {r0}
/*- Write in the IVR to support Protect Mode */
/*- No effect in Normal Mode */
/*- De-assert the NIRQ and clear the source in Protect Mode */
ldr r14, =AT91C_BASE_AIC
ldr r0 , [r14, #AIC_IVR]
str r14, [r14, #AIC_IVR]
/*- Enable Interrupt and Switch in Supervisor Mode */
msr CPSR_c, #ARM_MODE_SVC
/*- Save scratch/used registers and LR in User Stack */
stmfd sp!, { r1-r3, r12, r14}
/*- Branch to the routine pointed by the AIC_IVR */
mov r14, pc
bx r0
/*- Restore scratch/used registers and LR from User Stack*/
ldmia sp!, { r1-r3, r12, r14}
/*- Disable Interrupt and switch back in IRQ mode */
msr CPSR_c, #ARM_MODE_IRQ | I_BIT
/*- Mark the End of Interrupt on the AIC */
ldr r14, =AT91C_BASE_AIC
str r14, [r14, #AIC_EOICR]
/*- Restore SPSR_irq and r0 from IRQ stack */
ldmia sp!, {r0}
/*- Restore SPSR_irq and r0 from IRQ stack */
ldmia sp!, {r14}
msr SPSR_cxsf, r14
/*- Restore adjusted LR_irq from IRQ stack directly in the PC */
ldmia sp!, {pc}^
.endfunc
.end
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