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Diffstat (limited to 'arch/xtensa/kernel/head.S')
| -rw-r--r-- | arch/xtensa/kernel/head.S | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S new file mode 100644 index 000000000000..6e9b5225b8f6 --- /dev/null +++ b/arch/xtensa/kernel/head.S @@ -0,0 +1,237 @@ +/* + * 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 <xtensa/cacheasm.h> +#include <linux/config.h> +#include <asm/processor.h> +#include <asm/page.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) + * + */ + + .macro iterate from, to , cmd + .ifeq ((\to - \from) & ~0xfff) + \cmd \from + iterate "(\from+1)", \to, \cmd + .endif + .endm + +/* + * _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. + */ + + .section .head.text, "ax" + .globl _start +_start: _j 2f + .align 4 +1: .word _startup +2: l32r a0, 1b + jx a0 + + .text + .align 4 +_startup: + + /* Disable interrupts and exceptions. */ + + movi a0, XCHAL_PS_EXCM_MASK + 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 + + .macro reset_dbreak num + wsr a0, DBREAKC + \num + .endm + + iterate 0, XCHAL_NUM_IBREAK-1, reset_dbreak +#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. */ + + .macro reset_timer num + wsr a0, CCOMPARE_0 + \num + .endm + iterate 0, XCHAL_NUM_TIMERS-1, reset_timer + + /* 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. + * Does not include flushing writeback d-cache. + * a6, a7 are just working registers (clobbered). + */ + + icache_reset a2, a3 + dcache_reset a2, a3 + + /* 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 + +1: addi a2, a2, 4 + s32i a0, a2, 0 + blt a2, a3, 1b + +#if XCHAL_DCACHE_IS_WRITEBACK + + /* After unpacking, flush the writeback cache to memory so the + * instructions/data are available. + */ + + dcache_writeback_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 + + /* Define some common data structures here. We define them + * here in this assembly file due to their unusual alignment + * requirements. + */ + + .comm swapper_pg_dir,PAGE_SIZE,PAGE_SIZE + .comm empty_bad_page_table,PAGE_SIZE,PAGE_SIZE + .comm empty_bad_page,PAGE_SIZE,PAGE_SIZE + .comm empty_zero_page,PAGE_SIZE,PAGE_SIZE + |