mirror of
https://github.com/brain-hackers/u-boot-brain
synced 2024-07-09 20:56:16 +09:00
bbbe55f6f2
Enable the debug UART and emit a single 'a' early in the init sequence to show that it is working. Unfortunately the debug UART implementation needs a stack to work. I cannot seem to remove this limitation as the absolute 'jmp %eax' instruction goes off into the weeds. So this means that the character output cannot be any earlier than car_init_ret, where memory is available for a stack. Signed-off-by: Simon Glass <sjg@chromium.org> Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
286 lines
6.3 KiB
ArmAsm
286 lines
6.3 KiB
ArmAsm
/*
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* U-Boot - x86 Startup Code
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*
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* (C) Copyright 2008-2011
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* Graeme Russ, <graeme.russ@gmail.com>
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*
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* (C) Copyright 2002
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* Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <config.h>
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#include <asm/global_data.h>
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#include <asm/post.h>
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#include <asm/processor.h>
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#include <asm/processor-flags.h>
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#include <generated/generic-asm-offsets.h>
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#include <generated/asm-offsets.h>
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.section .text
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.code32
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.globl _start
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.type _start, @function
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.globl _x86boot_start
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_x86boot_start:
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/*
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* This is the fail-safe 32-bit bootstrap entry point.
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*
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* This code is used when booting from another boot loader like
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* coreboot or EFI. So we repeat some of the same init found in
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* start16.
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*/
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cli
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cld
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/* Turn off cache (this might require a 486-class CPU) */
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movl %cr0, %eax
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orl $(X86_CR0_NW | X86_CR0_CD), %eax
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movl %eax, %cr0
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wbinvd
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/* Tell 32-bit code it is being entered from an in-RAM copy */
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movl $GD_FLG_WARM_BOOT, %ebx
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/*
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* Zero the BIST (Built-In Self Test) value since we don't have it.
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* It must be 0 or the previous loader would have reported an error.
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*/
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movl $0, %ebp
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jmp 1f
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/* Add a way for tools to discover the _start entry point */
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.align 4
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.long 0x12345678
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_start:
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/*
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* This is the 32-bit cold-reset entry point, coming from start16.
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* Set %ebx to GD_FLG_COLD_BOOT to indicate this.
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*/
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movl $GD_FLG_COLD_BOOT, %ebx
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/* Save BIST */
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movl %eax, %ebp
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1:
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/* Save table pointer */
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movl %ecx, %esi
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/* Load the segement registers to match the GDT loaded in start16.S */
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movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
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movw %ax, %fs
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movw %ax, %ds
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movw %ax, %gs
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movw %ax, %es
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movw %ax, %ss
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/* Clear the interrupt vectors */
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lidt blank_idt_ptr
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/*
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* Critical early platform init - generally not used, we prefer init
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* to happen later when we have a console, in case something goes
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* wrong.
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*/
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jmp early_board_init
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.globl early_board_init_ret
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early_board_init_ret:
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post_code(POST_START)
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/* Initialise Cache-As-RAM */
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jmp car_init
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.globl car_init_ret
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car_init_ret:
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#ifndef CONFIG_HAVE_FSP
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/*
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* We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
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* or fully initialised SDRAM - we really don't care which)
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* starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
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* and early malloc() area. The MRC requires some space at the top.
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*
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* Stack grows down from top of CAR. We have:
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*
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* top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
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* MRC area
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* global_data
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* x86 global descriptor table
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* early malloc area
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* stack
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* bottom-> CONFIG_SYS_CAR_ADDR
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*/
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movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
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#ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
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subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
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#endif
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#else
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/*
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* When we get here after car_init(), esp points to a temporary stack
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* and esi holds the HOB list address returned by the FSP.
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*/
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#endif
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/* Reserve space on stack for global data */
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subl $GENERATED_GBL_DATA_SIZE, %esp
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/* Align global data to 16-byte boundary */
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andl $0xfffffff0, %esp
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post_code(POST_START_STACK)
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/*
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* Debug UART is available here although it may not be plumbed out
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* to pins depending on the board. To use it:
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*
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* call debug_uart_init
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* mov $'a', %eax
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* call printch
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*/
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/* Zero the global data since it won't happen later */
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xorl %eax, %eax
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movl $GENERATED_GBL_DATA_SIZE, %ecx
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movl %esp, %edi
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rep stosb
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#ifdef CONFIG_HAVE_FSP
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test %esi, %esi
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jz skip_hob
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/* Store HOB list */
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movl %esp, %edx
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addl $GD_HOB_LIST, %edx
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movl %esi, (%edx)
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skip_hob:
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#else
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/* Store table pointer */
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movl %esp, %edx
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addl $GD_TABLE, %edx
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movl %esi, (%edx)
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#endif
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/* Setup first parameter to setup_gdt, pointer to global_data */
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movl %esp, %eax
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/* Reserve space for global descriptor table */
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subl $X86_GDT_SIZE, %esp
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/* Align temporary global descriptor table to 16-byte boundary */
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andl $0xfffffff0, %esp
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movl %esp, %ecx
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#if defined(CONFIG_SYS_MALLOC_F_LEN)
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/* Set up the pre-relocation malloc pool */
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subl $CONFIG_SYS_MALLOC_F_LEN, %esp
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movl %eax, %edx
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addl $GD_MALLOC_BASE, %edx
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movl %esp, (%edx)
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#endif
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/* Store BIST into global_data */
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movl %eax, %edx
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addl $GD_BIST, %edx
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movl %ebp, (%edx)
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/* Set second parameter to setup_gdt() */
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movl %ecx, %edx
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/* Setup global descriptor table so gd->xyz works */
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call setup_gdt
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/* Set parameter to board_init_f() to boot flags */
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post_code(POST_START_DONE)
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xorl %eax, %eax
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/* Enter, U-Boot! */
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call board_init_f
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/* indicate (lack of) progress */
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movw $0x85, %ax
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jmp die
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.globl board_init_f_r_trampoline
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.type board_init_f_r_trampoline, @function
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board_init_f_r_trampoline:
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/*
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* SDRAM has been initialised, U-Boot code has been copied into
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* RAM, BSS has been cleared and relocation adjustments have been
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* made. It is now time to jump into the in-RAM copy of U-Boot
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*
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* %eax = Address of top of new stack
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*/
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/* Stack grows down from top of SDRAM */
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movl %eax, %esp
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/* Reserve space on stack for global data */
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subl $GENERATED_GBL_DATA_SIZE, %esp
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/* Align global data to 16-byte boundary */
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andl $0xfffffff0, %esp
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/* Setup first parameter to memcpy() and setup_gdt() */
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movl %esp, %eax
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/* Setup second parameter to memcpy() */
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fs movl 0, %edx
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/* Set third parameter to memcpy() */
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movl $GENERATED_GBL_DATA_SIZE, %ecx
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/* Copy global data from CAR to SDRAM stack */
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call memcpy
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/* Reserve space for global descriptor table */
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subl $X86_GDT_SIZE, %esp
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/* Align global descriptor table to 16-byte boundary */
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andl $0xfffffff0, %esp
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/* Set second parameter to setup_gdt() */
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movl %esp, %edx
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/* Setup global descriptor table so gd->xyz works */
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call setup_gdt
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/* Set if we need to disable CAR */
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.weak car_uninit
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movl $car_uninit, %eax
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cmpl $0, %eax
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jz 1f
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call car_uninit
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1:
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/* Re-enter U-Boot by calling board_init_f_r() */
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call board_init_f_r
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die:
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hlt
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jmp die
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hlt
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blank_idt_ptr:
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.word 0 /* limit */
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.long 0 /* base */
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.p2align 2 /* force 4-byte alignment */
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/* Add a multiboot header so U-Boot can be loaded by GRUB2 */
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multiboot_header:
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/* magic */
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.long 0x1badb002
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/* flags */
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.long (1 << 16)
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/* checksum */
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.long -0x1BADB002 - (1 << 16)
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/* header addr */
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.long multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
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/* load addr */
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.long CONFIG_SYS_TEXT_BASE
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/* load end addr */
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.long 0
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/* bss end addr */
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.long 0
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/* entry addr */
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.long CONFIG_SYS_TEXT_BASE
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