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Diffstat (limited to 'arch/xtensa/kernel/head.S')
| -rw-r--r-- | arch/xtensa/kernel/head.S | 386 |
1 files changed, 386 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S new file mode 100644 index 0000000000..8484294bc6 --- /dev/null +++ b/arch/xtensa/kernel/head.S @@ -0,0 +1,386 @@ +/* + * 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 <chris@zankel.net> + * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca> + * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com> + * 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) |