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>
19 #include <linux/linkage.h>
24 .type _start, @function
28 * This is the fail-safe 32-bit bootstrap entry point.
30 * This code is used when booting from another boot loader like
31 * coreboot or EFI. So we repeat some of the same init found in
37 /* Turn off cache (this might require a 486-class CPU) */
39 orl $(X86_CR0_NW | X86_CR0_CD), %eax
44 * Zero the BIST (Built-In Self Test) value since we don't have it.
45 * It must be 0 or the previous loader would have reported an error.
51 /* Add a way for tools to discover the _start entry point */
55 /* This is the 32-bit cold-reset entry point, coming from start16 */
61 /* Save table pointer */
64 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
68 /* Load the segement registers to match the GDT loaded in start16.S */
69 movl $(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
76 /* Clear the interrupt vectors */
80 * Critical early platform init - generally not used, we prefer init
81 * to happen later when we have a console, in case something goes
85 .globl early_board_init_ret
89 /* Initialise Cache-As-RAM */
93 #ifndef CONFIG_USE_HOB
95 * We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
96 * or fully initialised SDRAM - we really don't care which)
97 * starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
98 * and early malloc() area. The MRC requires some space at the top.
100 * Stack grows down from top of CAR. We have:
102 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
104 * global_data with x86 global descriptor table
107 * bottom-> CONFIG_SYS_CAR_ADDR
109 movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
110 #ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
111 subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
115 * U-Boot enters here twice. For the first time it comes from
116 * car_init_done() with esp points to a temporary stack and esi
117 * set to zero. For the second time it comes from fsp_init_done()
118 * with esi holding the HOB list address returned by the FSP.
121 /* Set up global data */
123 call board_init_f_alloc_reserve
125 call board_init_f_init_reserve
127 #ifdef CONFIG_DEBUG_UART
131 /* Get address of global_data */
133 #ifdef CONFIG_USE_HOB
134 /* Store the HOB list if we have one */
137 movl %esi, GD_HOB_LIST(%edx)
139 #ifdef CONFIG_HAVE_FSP
141 * After fsp_init() returns, the stack has already been switched to a
142 * place within system memory as defined by CONFIG_FSP_TEMP_RAM_ADDR.
143 * Enlarge the size of malloc() pool before relocation since we have
144 * plenty of memory now.
146 subl $CONFIG_FSP_SYS_MALLOC_F_LEN, %esp
147 movl %esp, GD_MALLOC_BASE(%edx)
151 /* Store table pointer */
152 movl %esi, GD_TABLE(%edx)
155 movl %ebp, GD_BIST(%edx)
157 /* Set parameter to board_init_f() to boot flags */
158 post_code(POST_START_DONE)
164 /* indicate (lack of) progress */
168 .globl board_init_f_r_trampoline
169 .type board_init_f_r_trampoline, @function
170 board_init_f_r_trampoline:
172 * SDRAM has been initialised, U-Boot code has been copied into
173 * RAM, BSS has been cleared and relocation adjustments have been
174 * made. It is now time to jump into the in-RAM copy of U-Boot
176 * %eax = Address of top of new stack
179 /* Stack grows down from top of SDRAM */
182 /* See if we need to disable CAR */
185 /* Re-enter U-Boot by calling board_init_f_r() */
190 .type jump_to_spl, @function
192 /* Reset stack to the top of CAR space */
193 movl $(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
194 #ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
195 subl $CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
214 .p2align 2 /* force 4-byte alignment */
216 /* Add a multiboot header so U-Boot can be loaded by GRUB2 */
223 .long -0x1BADB002 - (1 << 16)
225 .long multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
227 .long CONFIG_SYS_TEXT_BASE
233 .long CONFIG_SYS_TEXT_BASE
235 #ifdef CONFIG_X86_LOAD_FROM_32_BIT
237 * The following Global Descriptor Table is just enough to get us into
238 * 'Flat Protected Mode' - It will be discarded as soon as the final
239 * GDT is setup in a safe location in RAM
242 .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */
243 .long gdt_rom2 /* base */
245 /* Some CPUs are picky about GDT alignment... */
256 * 0x18 32bit data/stack
258 /* The NULL Desciptor - Mandatory */
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 */
266 /* Unused Desciptor - (matches Linux) */
267 .word 0x0000 /* limit_low */
268 .word 0x0000 /* base_low */
269 .byte 0x00 /* base_middle */
270 .byte 0x00 /* access */
271 .byte 0x00 /* flags + limit_high */
272 .byte 0x00 /* base_high */
275 * The Code Segment Descriptor:
276 * - Base = 0x00000000
278 * - Access = Present, Ring 0, Exec (Code), Readable
279 * - Flags = 4kB Granularity, 32-bit
281 .word 0xffff /* limit_low */
282 .word 0x0000 /* base_low */
283 .byte 0x00 /* base_middle */
284 .byte 0x9b /* access */
285 .byte 0xcf /* flags + limit_high */
286 .byte 0x00 /* base_high */
289 * The Data Segment Descriptor:
290 * - Base = 0x00000000
292 * - Access = Present, Ring 0, Non-Exec (Data), Writable
293 * - Flags = 4kB Granularity, 32-bit
295 .word 0xffff /* limit_low */
296 .word 0x0000 /* base_low */
297 .byte 0x00 /* base_middle */
298 .byte 0x93 /* access */
299 .byte 0xcf /* flags + limit_high */
300 .byte 0x00 /* base_high */