1 /* SPDX-License-Identifier: GPL-2.0+ */
3 * U-Boot - x86 Startup Code
5 * (C) Copyright 2008-2011
6 * Graeme Russ, <graeme.russ@gmail.com>
9 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
13 #include <asm/global_data.h>
15 #include <asm/processor.h>
16 #include <asm/processor-flags.h>
17 #include <generated/generic-asm-offsets.h>
18 #include <generated/asm-offsets.h>
23 .type _start, @function
27 * This is the fail-safe 32-bit bootstrap entry point.
29 * This code is used when booting from another boot loader like
30 * coreboot or EFI. So we repeat some of the same init found in
36 /* Turn off cache (this might require a 486-class CPU) */
38 orl $(X86_CR0_NW | X86_CR0_CD), %eax
42 /* Tell 32-bit code it is being entered from an in-RAM copy */
43 movl $GD_FLG_WARM_BOOT, %ebx
46 * Zero the BIST (Built-In Self Test) value since we don't have it.
47 * It must be 0 or the previous loader would have reported an error.
53 /* Add a way for tools to discover the _start entry point */
58 * This is the 32-bit cold-reset entry point, coming from start16.
59 * Set %ebx to GD_FLG_COLD_BOOT to indicate this.
61 movl $GD_FLG_COLD_BOOT, %ebx
67 /* Save table pointer */
70 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
74 /* Load the segement registers to match the GDT loaded in start16.S */
75 movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
82 /* Clear the interrupt vectors */
86 * Critical early platform init - generally not used, we prefer init
87 * to happen later when we have a console, in case something goes
91 .globl early_board_init_ret
95 /* Initialise Cache-As-RAM */
99 #ifndef CONFIG_HAVE_FSP
101 * We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
102 * or fully initialised SDRAM - we really don't care which)
103 * starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
104 * and early malloc() area. The MRC requires some space at the top.
106 * Stack grows down from top of CAR. We have:
108 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
110 * global_data with x86 global descriptor table
113 * bottom-> CONFIG_SYS_CAR_ADDR
115 movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
116 #ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
117 subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
121 * U-Boot enters here twice. For the first time it comes from
122 * car_init_done() with esp points to a temporary stack and esi
123 * set to zero. For the second time it comes from fsp_init_done()
124 * with esi holding the HOB list address returned by the FSP.
127 /* Set up global data */
129 call board_init_f_alloc_reserve
131 call board_init_f_init_reserve
133 #ifdef CONFIG_DEBUG_UART
137 /* Get address of global_data */
139 #ifdef CONFIG_HAVE_FSP
140 /* Store the HOB list if we have one */
143 movl %esi, GD_HOB_LIST(%edx)
146 * After fsp_init() returns, the stack has already been switched to a
147 * place within system memory as defined by CONFIG_FSP_TEMP_RAM_ADDR.
148 * Enlarge the size of malloc() pool before relocation since we have
149 * plenty of memory now.
151 subl $CONFIG_FSP_SYS_MALLOC_F_LEN, %esp
152 movl %esp, GD_MALLOC_BASE(%edx)
155 /* Store table pointer */
156 movl %esi, GD_TABLE(%edx)
159 movl %ebp, GD_BIST(%edx)
161 /* Set parameter to board_init_f() to boot flags */
162 post_code(POST_START_DONE)
168 /* indicate (lack of) progress */
172 .globl board_init_f_r_trampoline
173 .type board_init_f_r_trampoline, @function
174 board_init_f_r_trampoline:
176 * SDRAM has been initialised, U-Boot code has been copied into
177 * RAM, BSS has been cleared and relocation adjustments have been
178 * made. It is now time to jump into the in-RAM copy of U-Boot
180 * %eax = Address of top of new stack
183 /* Stack grows down from top of SDRAM */
186 /* See if we need to disable CAR */
188 movl $car_uninit, %eax
194 /* Re-enter U-Boot by calling board_init_f_r() */
206 .p2align 2 /* force 4-byte alignment */
208 /* Add a multiboot header so U-Boot can be loaded by GRUB2 */
215 .long -0x1BADB002 - (1 << 16)
217 .long multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
219 .long CONFIG_SYS_TEXT_BASE
225 .long CONFIG_SYS_TEXT_BASE
227 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
229 * The following Global Descriptor Table is just enough to get us into
230 * 'Flat Protected Mode' - It will be discarded as soon as the final
231 * GDT is setup in a safe location in RAM
234 .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */
235 .long gdt_rom2 /* base */
237 /* Some CPUs are picky about GDT alignment... */
248 * 0x18 32bit data/stack
250 /* The NULL Desciptor - Mandatory */
251 .word 0x0000 /* limit_low */
252 .word 0x0000 /* base_low */
253 .byte 0x00 /* base_middle */
254 .byte 0x00 /* access */
255 .byte 0x00 /* flags + limit_high */
256 .byte 0x00 /* base_high */
258 /* Unused Desciptor - (matches Linux) */
259 .word 0x0000 /* limit_low */
260 .word 0x0000 /* base_low */
261 .byte 0x00 /* base_middle */
262 .byte 0x00 /* access */
263 .byte 0x00 /* flags + limit_high */
264 .byte 0x00 /* base_high */
267 * The Code Segment Descriptor:
268 * - Base = 0x00000000
270 * - Access = Present, Ring 0, Exec (Code), Readable
271 * - Flags = 4kB Granularity, 32-bit
273 .word 0xffff /* limit_low */
274 .word 0x0000 /* base_low */
275 .byte 0x00 /* base_middle */
276 .byte 0x9b /* access */
277 .byte 0xcf /* flags + limit_high */
278 .byte 0x00 /* base_high */
281 * The Data Segment Descriptor:
282 * - Base = 0x00000000
284 * - Access = Present, Ring 0, Non-Exec (Data), Writable
285 * - Flags = 4kB Granularity, 32-bit
287 .word 0xffff /* limit_low */
288 .word 0x0000 /* base_low */
289 .byte 0x00 /* base_middle */
290 .byte 0x93 /* access */
291 .byte 0xcf /* flags + limit_high */
292 .byte 0x00 /* base_high */