1 /* SPDX-License-Identifier: GPL-2.0+ */
3 * U-Boot - x86 Startup Code
5 * This is always the first code to run from the U-Boot source. To spell it out:
7 * 1. When TPL (Tertiary Program Loader) is enabled, the boot flow is
8 * TPL->SPL->U-Boot and this file is used for TPL. Then start_from_tpl.S is used
9 * for SPL and start_from_spl.S is used for U-Boot proper.
11 * 2. When SPL (Secondary Program Loader) is enabled, but not TPL, the boot
12 * flow is SPL->U-Boot and this file is used for SPL. Then start_from_spl.S is
13 * used for U-Boot proper.
15 * 3. When neither TPL nor SPL is used, this file is used for U-Boot proper.
17 * (C) Copyright 2008-2011
18 * Graeme Russ, <graeme.russ@gmail.com>
21 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
25 #include <asm/global_data.h>
27 #include <asm/processor.h>
28 #include <asm/processor-flags.h>
29 #include <generated/generic-asm-offsets.h>
30 #include <generated/asm-offsets.h>
31 #include <linux/linkage.h>
36 .type _start, @function
40 * This is the fail-safe 32-bit bootstrap entry point.
42 * This code is used when booting from another boot loader like
43 * coreboot or EFI. So we repeat some of the same init found in
49 /* Turn off cache (this might require a 486-class CPU) */
51 orl $(X86_CR0_NW | X86_CR0_CD), %eax
56 * Zero the BIST (Built-In Self Test) value since we don't have it.
57 * It must be 0 or the previous loader would have reported an error.
63 /* Add a way for tools to discover the _start entry point */
67 /* This is the 32-bit cold-reset entry point, coming from start16 */
73 /* Save table pointer */
76 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
80 /* Load the segement registers to match the GDT loaded in start16.S */
81 movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
88 /* Clear the interrupt vectors */
92 * Critical early platform init - generally not used, we prefer init
93 * to happen later when we have a console, in case something goes
97 .globl early_board_init_ret
101 /* Initialise Cache-As-RAM */
105 #ifdef CONFIG_USE_CAR
107 * We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
108 * or fully initialised SDRAM - we really don't care which)
109 * starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
110 * and early malloc() area. The MRC requires some space at the top.
112 * Stack grows down from top of CAR. We have:
114 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
116 * global_data with x86 global descriptor table
119 * bottom-> CONFIG_SYS_CAR_ADDR
121 movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
122 #ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
123 subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
127 * U-Boot enters here twice. For the first time it comes from
128 * car_init_done() with esp points to a temporary stack and esi
129 * set to zero. For the second time it comes from fsp_init_done()
130 * with esi holding the HOB list address returned by the FSP.
133 /* Set up global data */
135 call board_init_f_alloc_reserve
137 call board_init_f_init_reserve
139 #ifdef CONFIG_DEBUG_UART
143 /* Get address of global_data */
145 #if defined(CONFIG_USE_HOB) && !defined(CONFIG_USE_CAR)
146 /* Store the HOB list if we have one */
149 movl %esi, GD_HOB_LIST(%edx)
151 #ifdef CONFIG_HAVE_FSP
153 * After fsp_init() returns, the stack has already been switched to a
154 * place within system memory as defined by CONFIG_FSP_TEMP_RAM_ADDR.
155 * Enlarge the size of malloc() pool before relocation since we have
156 * plenty of memory now.
158 subl $CONFIG_FSP_SYS_MALLOC_F_LEN, %esp
159 movl %esp, GD_MALLOC_BASE(%edx)
163 /* Store table pointer */
164 movl %esi, GD_TABLE(%edx)
167 movl %ebp, GD_BIST(%edx)
169 /* Set parameter to board_init_f() to boot flags */
170 post_code(POST_START_DONE)
176 /* indicate (lack of) progress */
180 .globl board_init_f_r_trampoline
181 .type board_init_f_r_trampoline, @function
182 board_init_f_r_trampoline:
184 * SDRAM has been initialised, U-Boot code has been copied into
185 * RAM, BSS has been cleared and relocation adjustments have been
186 * made. It is now time to jump into the in-RAM copy of U-Boot
188 * %eax = Address of top of new stack
191 /* Stack grows down from top of SDRAM */
194 /* See if we need to disable CAR */
197 /* Re-enter U-Boot by calling board_init_f_r() */
202 .type jump_to_spl, @function
204 /* Reset stack to the top of CAR space */
205 movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
206 #ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
207 subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
226 .p2align 2 /* force 4-byte alignment */
228 /* Add a multiboot header so U-Boot can be loaded by GRUB2 */
235 .long -0x1BADB002 - (1 << 16)
237 .long multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
239 .long CONFIG_SYS_TEXT_BASE
245 .long CONFIG_SYS_TEXT_BASE
247 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
249 * The following Global Descriptor Table is just enough to get us into
250 * 'Flat Protected Mode' - It will be discarded as soon as the final
251 * GDT is setup in a safe location in RAM
254 .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */
255 .long gdt_rom2 /* base */
257 /* Some CPUs are picky about GDT alignment... */
268 * 0x18 32bit data/stack
270 /* The NULL Desciptor - Mandatory */
271 .word 0x0000 /* limit_low */
272 .word 0x0000 /* base_low */
273 .byte 0x00 /* base_middle */
274 .byte 0x00 /* access */
275 .byte 0x00 /* flags + limit_high */
276 .byte 0x00 /* base_high */
278 /* Unused Desciptor - (matches Linux) */
279 .word 0x0000 /* limit_low */
280 .word 0x0000 /* base_low */
281 .byte 0x00 /* base_middle */
282 .byte 0x00 /* access */
283 .byte 0x00 /* flags + limit_high */
284 .byte 0x00 /* base_high */
287 * The Code Segment Descriptor:
288 * - Base = 0x00000000
290 * - Access = Present, Ring 0, Exec (Code), Readable
291 * - Flags = 4kB Granularity, 32-bit
293 .word 0xffff /* limit_low */
294 .word 0x0000 /* base_low */
295 .byte 0x00 /* base_middle */
296 .byte 0x9b /* access */
297 .byte 0xcf /* flags + limit_high */
298 .byte 0x00 /* base_high */
301 * The Data Segment Descriptor:
302 * - Base = 0x00000000
304 * - Access = Present, Ring 0, Non-Exec (Data), Writable
305 * - Flags = 4kB Granularity, 32-bit
307 .word 0xffff /* limit_low */
308 .word 0x0000 /* base_low */
309 .byte 0x00 /* base_middle */
310 .byte 0x93 /* access */
311 .byte 0xcf /* flags + limit_high */
312 .byte 0x00 /* base_high */