x86/cpu/start.S

1 /* SPDX-License-Identifier: GPL-2.0+ */
3  *  U-Boot - x86 Startup Code
5  * (C) Copyright 2008-2011
16 #include <asm/processor-flags.h>
17 #include <generated/generic-asm-offsets.h>
18 #include <generated/asm-offsets.h>
28 	 * This is the fail-safe 32-bit bootstrap entry point.
37 	/* Turn off cache (this might require a 486-class CPU) */
43 	/* Tell 32-bit code it is being entered from an in-RAM copy */
47 	 * Zero the BIST (Built-In Self Test) value since we don't have it.
59 	 * This is the 32-bit cold-reset entry point, coming from start16.
87 	 * Critical early platform init - generally not used, we prefer init
96 	/* Initialise Cache-As-RAM */
102 	 * We now have CONFIG_SYS_CAR_SIZE bytes of Cache-As-RAM (or SRAM,
103 	 * or fully initialised SDRAM - we really don't care which)
109 	 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
114 	 * bottom-> CONFIG_SYS_CAR_ADDR
116 	movl	$(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
122 	 * U-Boot enters here twice. For the first time it comes from
124 	 * set to zero. For the second time it comes from fsp_init_done()
166 	/* Enter, U-Boot! */
177 	 * SDRAM has been initialised, U-Boot code has been copied into
179 	 * made. It is now time to jump into the in-RAM copy of U-Boot
190 	/* 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
230 	 * 'Flat Protected Mode' - It will be discarded as soon as the final
234 	.word	0x1f		/* limit (31 bytes = 4 GDT entries - 1) */
250 	/* The NULL Desciptor - Mandatory */
258 	/* Unused Desciptor - (matches Linux) */
268 	 * - Base   = 0x00000000
269 	 * - Size   = 4GB
270 	 * - Access = Present, Ring 0, Exec (Code), Readable
271 	 * - Flags  = 4kB Granularity, 32-bit
282 	 * - Base   = 0x00000000
283 	 * - Size   = 4GB
284 	 * - Access = Present, Ring 0, Non-Exec (Data), Writable
285 	 * - Flags  = 4kB Granularity, 32-bit