/* * 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 * Marc Gauthier * Joe Taylor * Kevin Chea */ #include #include #include #include #include #include /* * 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 _SetupMMU .align 4 .literal_position .Lstartup: .word _startup .align 4 .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, 0x08000000 bgeu a2, a3, 1f movi a3, 0xd0000000 add a2, a2, a3 wsr a2, excsave1 1: #endif #endif .end no-absolute-literals l32r a0, .Lstartup jx a0 ENDPROC(_start) __INIT .literal_position ENTRY(_startup) /* Disable interrupts and exceptions. */ movi a0, LOCKLEVEL wsr a0, ps /* 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 #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 - 1 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 /* Set PS.INTLEVEL=LOCKLEVEL, 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, LOCKLEVEL 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_stop # 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 memw isync ___invalidate_icache_all a2 a3 isync /* Setup stack and enable window exceptions (keep irqs disabled) */ movi a1, init_thread_union addi a1, a1, KERNEL_STACK_SIZE movi a2, (1 << PS_WOE_BIT) | LOCKLEVEL # WOE=1, INTLEVEL=LOCKLEVEL, 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, SREG_EXCSAVE + XCHAL_DEBUGLEVEL /* Set up EXCSAVE[1] to point to the exc_table. */ movi a6, exc_table xsr a6, excsave1 /* 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 ENDPROC(_startup) /* * 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)