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u-boot/cpu/at32ap/start.S
Haavard Skinnemoen caf83ea888 avr32: Use the same entry point for reset and exception handling 
Since the reset vector is always aligned to a very large boundary, we
can save a couple of KB worth of alignment padding by placing the
exception vectors at the same address.

Deciding which one it is is easy: If we're handling an exception, the
CPU is in Exception mode. If we're starting up after reset, the CPU is
in Supervisor mode. So this adds a very minimal overhead to the reset
path (only executed once) and the exception handling path (normally
never executed at all.)

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
2008-05-27 15:27:30 +02:00

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/*
* Copyright (C) 2005-2008 Atmel Corporation
*
* See file CREDITS for list of people who contributed to this
* project.
*
* 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; either version 2 of
* the License, or (at your option) any later version.
*
* 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
*/
#include <config.h>
#include <asm/ptrace.h>
#include <asm/sysreg.h>
#define SYSREG_MMUCR_I_OFFSET 2
#define SYSREG_MMUCR_S_OFFSET 4
#define SR_INIT (SYSREG_BIT(GM) | SYSREG_BIT(EM) | SYSREG_BIT(M0))
#define CPUCR_INIT (SYSREG_BIT(BI) | SYSREG_BIT(BE) \
| SYSREG_BIT(FE) | SYSREG_BIT(RE) \
| SYSREG_BIT(IBE) | SYSREG_BIT(IEE))
/*
* To save some space, we use the same entry point for
* exceptions and reset. This avoids lots of alignment padding
* since the reset vector is always suitably aligned.
*/
.section .exception.text, "ax", @progbits
.global _start
.global _evba
.type _start, @function
.type _evba, @function
_start:
.size _start, 0
_evba:
.org 0x00
rjmp unknown_exception /* Unrecoverable exception */
.org 0x04
rjmp unknown_exception /* TLB multiple hit */
.org 0x08
rjmp unknown_exception /* Bus error data fetch */
.org 0x0c
rjmp unknown_exception /* Bus error instruction fetch */
.org 0x10
rjmp unknown_exception /* NMI */
.org 0x14
rjmp unknown_exception /* Instruction address */
.org 0x18
rjmp unknown_exception /* ITLB protection */
.org 0x1c
rjmp unknown_exception /* Breakpoint */
.org 0x20
rjmp unknown_exception /* Illegal opcode */
.org 0x24
rjmp unknown_exception /* Unimplemented instruction */
.org 0x28
rjmp unknown_exception /* Privilege violation */
.org 0x2c
rjmp unknown_exception /* Floating-point */
.org 0x30
rjmp unknown_exception /* Coprocessor absent */
.org 0x34
rjmp unknown_exception /* Data Address (read) */
.org 0x38
rjmp unknown_exception /* Data Address (write) */
.org 0x3c
rjmp unknown_exception /* DTLB Protection (read) */
.org 0x40
rjmp unknown_exception /* DTLB Protection (write) */
.org 0x44
rjmp unknown_exception /* DTLB Modified */
.org 0x50
rjmp unknown_exception /* ITLB Miss */
.org 0x60
rjmp unknown_exception /* DTLB Miss (read) */
.org 0x70
rjmp unknown_exception /* DTLB Miss (write) */
.size _evba, . - _evba
.align 2
.type unknown_exception, @function
unknown_exception:
/* Figure out whether we're handling an exception (Exception
* mode) or just booting (Supervisor mode). */
csrfcz SYSREG_M1_OFFSET
brcc at32ap_cpu_bootstrap
/* This is an exception. Complain. */
pushm r0-r12
sub r8, sp, REG_R12 - REG_R0 - 4
mov r9, lr
mfsr r10, SYSREG_RAR_EX
mfsr r11, SYSREG_RSR_EX
pushm r8-r11
mfsr r12, SYSREG_ECR
mov r11, sp
rcall do_unknown_exception
1: rjmp 1b
/* The COUNT/COMPARE timer interrupt handler */
.global timer_interrupt_handler
.type timer_interrupt_handler,@function
.align 2
timer_interrupt_handler:
/*
* Increment timer_overflow and re-write COMPARE with 0xffffffff.
*
* We're running at interrupt level 3, so we don't need to save
* r8-r12 or lr to the stack.
*/
lda.w r8, timer_overflow
ld.w r9, r8[0]
mov r10, -1
mtsr SYSREG_COMPARE, r10
sub r9, -1
st.w r8[0], r9
rete
/*
* CPU bootstrap after reset is handled here. SoC code may
* override this in case they need to initialize oscillators,
* etc.
*/
.section .text.at32ap_cpu_bootstrap, "ax", @progbits
.global at32ap_cpu_bootstrap
.weak at32ap_cpu_bootstrap
.type at32ap_cpu_bootstrap, @function
.align 2
at32ap_cpu_bootstrap:
/* Reset the Status Register */
mov r0, lo(SR_INIT)
orh r0, hi(SR_INIT)
mtsr SYSREG_SR, r0
/* Reset CPUCR and invalidate the BTB */
mov r2, CPUCR_INIT
mtsr SYSREG_CPUCR, r2
/* Flush the caches */
mov r1, 0
cache r1[4], 8
cache r1[0], 0
sync 0
/* Reset the MMU to default settings */
mov r0, SYSREG_BIT(MMUCR_S) | SYSREG_BIT(MMUCR_I)
mtsr SYSREG_MMUCR, r0
/* Internal RAM should not need any initialization. We might
have to initialize external RAM here if the part doesn't
have internal RAM (or we may use the data cache) */
/* Jump to cacheable segment */
lddpc pc, 1f
.align 2
1: .long at32ap_low_level_init
.size _start, . - _start
/* Common CPU bootstrap code after oscillator/cache/etc. init */
.section .text.avr32ap_low_level_init, "ax", @progbits
.global at32ap_low_level_init
.type at32ap_low_level_init, @function
.align 2
at32ap_low_level_init:
lddpc sp, sp_init
/* Initialize the GOT pointer */
lddpc r6, got_init
3: rsub r6, pc
/* Let's go */
rjmp board_init_f
.align 2
.type sp_init,@object
sp_init:
.long CFG_INIT_SP_ADDR
got_init:
.long 3b - _GLOBAL_OFFSET_TABLE_
/*
* void relocate_code(new_sp, new_gd, monitor_addr)
*
* Relocate the u-boot image into RAM and continue from there.
* Does not return.
*/
.section .text.relocate_code,"ax",@progbits
.global relocate_code
.type relocate_code,@function
relocate_code:
mov sp, r12 /* use new stack */
mov r12, r11 /* save new_gd */
mov r11, r10 /* save destination address */
/* copy .text section and flush the cache along the way */
lda.w r8, _text
lda.w r9, _etext
sub lr, r10, r8 /* relocation offset */
1: ldm r8++, r0-r3
stm r10, r0-r3
sub r10, -16
ldm r8++, r0-r3
stm r10, r0-r3
sub r10, -16
cp.w r8, r9
cache r10[-4], 0x0d /* dcache clean/invalidate */
cache r10[-4], 0x01 /* icache invalidate */
brlt 1b
/* flush write buffer */
sync 0
/* copy data sections */
lda.w r9, _edata
1: ld.d r0, r8++
st.d r10++, r0
cp.w r8, r9
brlt 1b
/* zero out .bss */
mov r0, 0
mov r1, 0
lda.w r9, _end
sub r9, r8
1: st.d r10++, r0
sub r9, 8
brgt 1b
/* jump to RAM */
sub r0, pc, . - in_ram
add pc, r0, lr
.align 2
in_ram:
/* find the new GOT and relocate it */
lddpc r6, got_init_reloc
3: rsub r6, pc
mov r8, r6
lda.w r9, _egot
lda.w r10, _got
sub r9, r10
1: ld.w r0, r8[0]
add r0, lr
st.w r8++, r0
sub r9, 4
brgt 1b
/* Move the exception handlers */
mfsr r2, SYSREG_EVBA
add r2, lr
mtsr SYSREG_EVBA, r2
/* Do the rest of the initialization sequence */
call board_init_r
.align 2
got_init_reloc:
.long 3b - _GLOBAL_OFFSET_TABLE_
.size relocate_code, . - relocate_code
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