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head.S
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/*
* 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 - 2008 Tensilica Inc.
*
* Chris Zankel <[email protected]>
* Marc Gauthier <[email protected], [email protected]>
* Joe Taylor <[email protected], [email protected]>
* Kevin Chea
*/
#include <asm/asmmacro.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/cacheasm.h>
#include <asm/initialize_mmu.h>
#include <asm/mxregs.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
.begin no-absolute-literals
ENTRY(_start)
/* Preserve the pointer to the boot parameter list in EXCSAVE_1 */
wsr a2, excsave1
_j _SetupOCD
.align 4
.literal_position
_SetupOCD:
/*
* Initialize WB, WS, and clear PS.EXCM (to allow loop instructions).
* Set Interrupt Level just below XCHAL_DEBUGLEVEL to allow
* xt-gdb to single step via DEBUG exceptions received directly
* by ocd.
*/
#if XCHAL_HAVE_WINDOWED
movi a1, 1
movi a0, 0
wsr a1, windowstart
wsr a0, windowbase
rsync
#endif
movi a1, LOCKLEVEL
wsr a1, ps
rsync
.global _SetupMMU
_SetupMMU:
Offset = _SetupMMU - _start
#ifdef CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
initialize_mmu
#if defined(CONFIG_MMU) && XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY
rsr a2, excsave1
movi a3, XCHAL_KSEG_PADDR
bltu a2, a3, 1f
sub a2, a2, a3
movi a3, XCHAL_KSEG_SIZE
bgeu a2, a3, 1f
movi a3, XCHAL_KSEG_CACHED_VADDR
add a2, a2, a3
wsr a2, excsave1
1:
#endif
#endif
movi a0, _startup
jx a0
ENDPROC(_start)
.end no-absolute-literals
__REF
.literal_position
ENTRY(_startup)
/* Set a0 to 0 for the remaining initialization. */
movi a0, 0
#if XCHAL_HAVE_VECBASE
movi a2, VECBASE_VADDR
wsr a2, vecbase
#endif
/* Clear debugging registers. */
#if XCHAL_HAVE_DEBUG
#if XCHAL_NUM_IBREAK > 0
wsr a0, ibreakenable
#endif
wsr a0, icount
movi a1, 15
wsr a0, icountlevel
.set _index, 0
.rept XCHAL_NUM_DBREAK
wsr a0, SREG_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
wsr a0, SREG_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_HAVE_CP
wsr a0, cpenable
#endif
/* 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
initialize_cacheattr
#ifdef CONFIG_HAVE_SMP
movi a2, CCON # MX External Register to Configure Cache
movi a3, 1
wer a3, a2
#endif
/* Setup stack and enable window exceptions (keep irqs disabled) */
movi a1, start_info
l32i a1, a1, 0
/* Disable interrupts. */
/* Enable window exceptions if kernel is built with windowed ABI. */
movi a2, KERNEL_PS_WOE_MASK | LOCKLEVEL
wsr a2, ps
rsync
#ifdef CONFIG_SMP
/*
* Notice that we assume with SMP that cores have PRID
* supported by the cores.
*/
rsr a2, prid
bnez a2, .Lboot_secondary
#endif /* CONFIG_SMP */
/* Unpack data sections
*
* The linker script used to build the Linux kernel image
* creates a table located at __boot_reloc_table_start
* that contains 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 destination (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_stop # end of BSS
__loopt a2, a3, a4, 2
s32i a0, a2, 0
__endla a2, a3, 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
memw
isync
___invalidate_icache_all a2 a3
isync
#ifdef CONFIG_XIP_KERNEL
/* Setup bootstrap CPU stack in XIP kernel */
movi a1, start_info
l32i a1, a1, 0
#endif
movi abi_arg0, 0
xsr abi_arg0, excsave1
/* init_arch kick-starts the linux kernel */
abi_call init_arch
abi_call start_kernel
should_never_return:
j should_never_return
#ifdef CONFIG_SMP
.Lboot_secondary:
movi a2, cpu_start_ccount
1:
memw
l32i a3, a2, 0
beqi a3, 0, 1b
movi a3, 0
s32i a3, a2, 0
1:
memw
l32i a3, a2, 0
beqi a3, 0, 1b
wsr a3, ccount
movi a3, 0
s32i a3, a2, 0
memw
movi abi_arg0, 0
wsr abi_arg0, excsave1
abi_call secondary_start_kernel
j should_never_return
#endif /* CONFIG_SMP */
ENDPROC(_startup)
#ifdef CONFIG_HOTPLUG_CPU
ENTRY(cpu_restart)
#if XCHAL_DCACHE_IS_WRITEBACK
___flush_invalidate_dcache_all a2 a3
#else
___invalidate_dcache_all a2 a3
#endif
memw
movi a2, CCON # MX External Register to Configure Cache
movi a3, 0
wer a3, a2
extw
rsr a0, prid
neg a2, a0
movi a3, cpu_start_id
memw
s32i a2, a3, 0
#if XCHAL_DCACHE_IS_WRITEBACK
dhwbi a3, 0
#endif
1:
memw
l32i a2, a3, 0
dhi a3, 0
bne a2, a0, 1b
/*
* Initialize WB, WS, and clear PS.EXCM (to allow loop instructions).
* Set Interrupt Level just below XCHAL_DEBUGLEVEL to allow
* xt-gdb to single step via DEBUG exceptions received directly
* by ocd.
*/
movi a1, 1
movi a0, 0
wsr a1, windowstart
wsr a0, windowbase
rsync
movi a1, LOCKLEVEL
wsr a1, ps
rsync
j _startup
ENDPROC(cpu_restart)
#endif /* CONFIG_HOTPLUG_CPU */
/*
* DATA section
*/
__REFDATA
.align 4
ENTRY(start_info)
.long init_thread_union + KERNEL_STACK_SIZE
/*
* BSS section
*/
__PAGE_ALIGNED_BSS
#ifdef CONFIG_MMU
ENTRY(swapper_pg_dir)
.fill PAGE_SIZE, 1, 0
END(swapper_pg_dir)
#endif
ENTRY(empty_zero_page)
.fill PAGE_SIZE, 1, 0
END(empty_zero_page)