forked from Minki/linux
0ebdcb4d04
Signed-off-by: Tim Abbott <tabbott@mit.edu> Cc: Chris Zankel <chris@zankel.net> Acked-by: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
245 lines
4.8 KiB
ArmAsm
245 lines
4.8 KiB
ArmAsm
/*
|
|
* arch/xtensa/kernel/head.S
|
|
*
|
|
* Xtensa Processor startup code.
|
|
*
|
|
* This file is subject to the terms and conditions of the GNU General Public
|
|
* License. See the file "COPYING" in the main directory of this archive
|
|
* for more details.
|
|
*
|
|
* Copyright (C) 2001 - 2005 Tensilica Inc.
|
|
*
|
|
* Chris Zankel <chris@zankel.net>
|
|
* Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
|
|
* Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
|
|
* Kevin Chea
|
|
*/
|
|
|
|
#include <asm/processor.h>
|
|
#include <asm/page.h>
|
|
#include <asm/cacheasm.h>
|
|
|
|
#include <linux/init.h>
|
|
#include <linux/linkage.h>
|
|
|
|
/*
|
|
* This module contains the entry code for kernel images. It performs the
|
|
* minimal setup needed to call the generic C routines.
|
|
*
|
|
* Prerequisites:
|
|
*
|
|
* - The kernel image has been loaded to the actual address where it was
|
|
* compiled to.
|
|
* - a2 contains either 0 or a pointer to a list of boot parameters.
|
|
* (see setup.c for more details)
|
|
*
|
|
*/
|
|
|
|
/*
|
|
* _start
|
|
*
|
|
* The bootloader passes a pointer to a list of boot parameters in a2.
|
|
*/
|
|
|
|
/* The first bytes of the kernel image must be an instruction, so we
|
|
* manually allocate and define the literal constant we need for a jx
|
|
* instruction.
|
|
*/
|
|
|
|
__HEAD
|
|
.globl _start
|
|
_start: _j 2f
|
|
.align 4
|
|
1: .word _startup
|
|
2: l32r a0, 1b
|
|
jx a0
|
|
|
|
.section .init.text, "ax"
|
|
.align 4
|
|
_startup:
|
|
|
|
/* Disable interrupts and exceptions. */
|
|
|
|
movi a0, LOCKLEVEL
|
|
wsr a0, PS
|
|
|
|
/* Preserve the pointer to the boot parameter list in EXCSAVE_1 */
|
|
|
|
wsr a2, EXCSAVE_1
|
|
|
|
/* Start with a fresh windowbase and windowstart. */
|
|
|
|
movi a1, 1
|
|
movi a0, 0
|
|
wsr a1, WINDOWSTART
|
|
wsr a0, WINDOWBASE
|
|
rsync
|
|
|
|
/* Set a0 to 0 for the remaining initialization. */
|
|
|
|
movi a0, 0
|
|
|
|
/* Clear debugging registers. */
|
|
|
|
#if XCHAL_HAVE_DEBUG
|
|
wsr a0, IBREAKENABLE
|
|
wsr a0, ICOUNT
|
|
movi a1, 15
|
|
wsr a0, ICOUNTLEVEL
|
|
|
|
.set _index, 0
|
|
.rept XCHAL_NUM_DBREAK - 1
|
|
wsr a0, DBREAKC + _index
|
|
.set _index, _index + 1
|
|
.endr
|
|
#endif
|
|
|
|
/* Clear CCOUNT (not really necessary, but nice) */
|
|
|
|
wsr a0, CCOUNT # not really necessary, but nice
|
|
|
|
/* Disable zero-loops. */
|
|
|
|
#if XCHAL_HAVE_LOOPS
|
|
wsr a0, LCOUNT
|
|
#endif
|
|
|
|
/* Disable all timers. */
|
|
|
|
.set _index, 0
|
|
.rept XCHAL_NUM_TIMERS - 1
|
|
wsr a0, CCOMPARE + _index
|
|
.set _index, _index + 1
|
|
.endr
|
|
|
|
/* Interrupt initialization. */
|
|
|
|
movi a2, XCHAL_INTTYPE_MASK_SOFTWARE | XCHAL_INTTYPE_MASK_EXTERN_EDGE
|
|
wsr a0, INTENABLE
|
|
wsr a2, INTCLEAR
|
|
|
|
/* Disable coprocessors. */
|
|
|
|
#if XCHAL_CP_NUM > 0
|
|
wsr a0, CPENABLE
|
|
#endif
|
|
|
|
/* Set PS.INTLEVEL=1, PS.WOE=0, kernel stack, PS.EXCM=0
|
|
*
|
|
* Note: PS.EXCM must be cleared before using any loop
|
|
* instructions; otherwise, they are silently disabled, and
|
|
* at most one iteration of the loop is executed.
|
|
*/
|
|
|
|
movi a1, 1
|
|
wsr a1, PS
|
|
rsync
|
|
|
|
/* Initialize the caches.
|
|
* a2, a3 are just working registers (clobbered).
|
|
*/
|
|
|
|
#if XCHAL_DCACHE_LINE_LOCKABLE
|
|
___unlock_dcache_all a2 a3
|
|
#endif
|
|
|
|
#if XCHAL_ICACHE_LINE_LOCKABLE
|
|
___unlock_icache_all a2 a3
|
|
#endif
|
|
|
|
___invalidate_dcache_all a2 a3
|
|
___invalidate_icache_all a2 a3
|
|
|
|
isync
|
|
|
|
/* Unpack data sections
|
|
*
|
|
* The linker script used to build the Linux kernel image
|
|
* creates a table located at __boot_reloc_table_start
|
|
* that contans the information what data needs to be unpacked.
|
|
*
|
|
* Uses a2-a7.
|
|
*/
|
|
|
|
movi a2, __boot_reloc_table_start
|
|
movi a3, __boot_reloc_table_end
|
|
|
|
1: beq a2, a3, 3f # no more entries?
|
|
l32i a4, a2, 0 # start destination (in RAM)
|
|
l32i a5, a2, 4 # end desination (in RAM)
|
|
l32i a6, a2, 8 # start source (in ROM)
|
|
addi a2, a2, 12 # next entry
|
|
beq a4, a5, 1b # skip, empty entry
|
|
beq a4, a6, 1b # skip, source and dest. are the same
|
|
|
|
2: l32i a7, a6, 0 # load word
|
|
addi a6, a6, 4
|
|
s32i a7, a4, 0 # store word
|
|
addi a4, a4, 4
|
|
bltu a4, a5, 2b
|
|
j 1b
|
|
|
|
3:
|
|
/* All code and initialized data segments have been copied.
|
|
* Now clear the BSS segment.
|
|
*/
|
|
|
|
movi a2, _bss_start # start of BSS
|
|
movi a3, _bss_end # end of BSS
|
|
|
|
__loopt a2, a3, a4, 2
|
|
s32i a0, a2, 0
|
|
__endla a2, a4, 4
|
|
|
|
#if XCHAL_DCACHE_IS_WRITEBACK
|
|
|
|
/* After unpacking, flush the writeback cache to memory so the
|
|
* instructions/data are available.
|
|
*/
|
|
|
|
___flush_dcache_all a2 a3
|
|
#endif
|
|
|
|
/* Setup stack and enable window exceptions (keep irqs disabled) */
|
|
|
|
movi a1, init_thread_union
|
|
addi a1, a1, KERNEL_STACK_SIZE
|
|
|
|
movi a2, 0x00040001 # WOE=1, INTLEVEL=1, UM=0
|
|
wsr a2, PS # (enable reg-windows; progmode stack)
|
|
rsync
|
|
|
|
/* Set up EXCSAVE[DEBUGLEVEL] to point to the Debug Exception Handler.*/
|
|
|
|
movi a2, debug_exception
|
|
wsr a2, EXCSAVE + XCHAL_DEBUGLEVEL
|
|
|
|
/* Set up EXCSAVE[1] to point to the exc_table. */
|
|
|
|
movi a6, exc_table
|
|
xsr a6, EXCSAVE_1
|
|
|
|
/* init_arch kick-starts the linux kernel */
|
|
|
|
movi a4, init_arch
|
|
callx4 a4
|
|
|
|
movi a4, start_kernel
|
|
callx4 a4
|
|
|
|
should_never_return:
|
|
j should_never_return
|
|
|
|
|
|
/*
|
|
* BSS section
|
|
*/
|
|
|
|
.section ".bss.page_aligned", "w"
|
|
#ifdef CONFIG_MMU
|
|
ENTRY(swapper_pg_dir)
|
|
.fill PAGE_SIZE, 1, 0
|
|
#endif
|
|
ENTRY(empty_zero_page)
|
|
.fill PAGE_SIZE, 1, 0
|