xref: /openbmc/u-boot/arch/x86/cpu/start.S (revision 2f07a9a6)
1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 *  U-Boot - x86 Startup Code
4 *
5 * (C) Copyright 2008-2011
6 * Graeme Russ, <graeme.russ@gmail.com>
7 *
8 * (C) Copyright 2002
9 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
10 */
11
12#include <config.h>
13#include <asm/global_data.h>
14#include <asm/post.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>
20
21.section .text.start
22.code32
23.globl _start
24.type _start, @function
25.globl _x86boot_start
26_x86boot_start:
27	/*
28	 * This is the fail-safe 32-bit bootstrap entry point.
29	 *
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
32	 * start16.
33	 */
34	cli
35	cld
36
37	/* Turn off cache (this might require a 486-class CPU) */
38	movl	%cr0, %eax
39	orl	$(X86_CR0_NW | X86_CR0_CD), %eax
40	movl	%eax, %cr0
41	wbinvd
42
43	/* Tell 32-bit code it is being entered from an in-RAM copy */
44	movl	$GD_FLG_WARM_BOOT, %ebx
45
46	/*
47	 * Zero the BIST (Built-In Self Test) value since we don't have it.
48	 * It must be 0 or the previous loader would have reported an error.
49	 */
50	movl	$0, %ebp
51
52	jmp	1f
53
54	/* Add a way for tools to discover the _start entry point */
55	.align	4
56	.long	0x12345678
57_start:
58	/*
59	 * This is the 32-bit cold-reset entry point, coming from start16.
60	 * Set %ebx to GD_FLG_COLD_BOOT to indicate this.
61	 */
62	movl	$GD_FLG_COLD_BOOT, %ebx
63
64	/* Save BIST */
65	movl	%eax, %ebp
661:
67
68	/* Save table pointer */
69	movl	%ecx, %esi
70
71#ifdef CONFIG_X86_LOAD_FROM_32_BIT
72	lgdt	gdt_ptr2
73#endif
74
75	/* Load the segement registers to match the GDT loaded in start16.S */
76	movl	$(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
77	movw	%ax, %fs
78	movw	%ax, %ds
79	movw	%ax, %gs
80	movw	%ax, %es
81	movw	%ax, %ss
82
83	/* Clear the interrupt vectors */
84	lidt	blank_idt_ptr
85
86	/*
87	 * Critical early platform init - generally not used, we prefer init
88	 * to happen later when we have a console, in case something goes
89	 * wrong.
90	 */
91	jmp	early_board_init
92.globl early_board_init_ret
93early_board_init_ret:
94	post_code(POST_START)
95
96	/* Initialise Cache-As-RAM */
97	jmp	car_init
98.globl car_init_ret
99car_init_ret:
100#ifndef CONFIG_HAVE_FSP
101	/*
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)
104	 * starting at CONFIG_SYS_CAR_ADDR to be used as a temporary stack
105	 * and early malloc() area. The MRC requires some space at the top.
106	 *
107	 * Stack grows down from top of CAR. We have:
108	 *
109	 * top-> CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE
110	 *	MRC area
111	 *	global_data with x86 global descriptor table
112	 *	early malloc area
113	 *	stack
114	 * bottom-> CONFIG_SYS_CAR_ADDR
115	 */
116	movl	$(CONFIG_SYS_CAR_ADDR + CONFIG_SYS_CAR_SIZE - 4), %esp
117#ifdef CONFIG_DCACHE_RAM_MRC_VAR_SIZE
118	subl	$CONFIG_DCACHE_RAM_MRC_VAR_SIZE, %esp
119#endif
120#else
121	/*
122	 * U-Boot enters here twice. For the first time it comes from
123	 * car_init_done() with esp points to a temporary stack and esi
124	 * set to zero. For the second time it comes from fsp_init_done()
125	 * with esi holding the HOB list address returned by the FSP.
126	 */
127#endif
128	/* Set up global data */
129	mov	%esp, %eax
130	call	board_init_f_alloc_reserve
131	mov	%eax, %esp
132	call	board_init_f_init_reserve
133
134#ifdef CONFIG_DEBUG_UART
135	call	debug_uart_init
136#endif
137
138	/* Get address of global_data */
139	mov	%fs:0, %edx
140#ifdef CONFIG_HAVE_FSP
141	/* Store the HOB list if we have one */
142	test	%esi, %esi
143	jz	skip_hob
144	movl	%esi, GD_HOB_LIST(%edx)
145
146	/*
147	 * After fsp_init() returns, the stack has already been switched to a
148	 * place within system memory as defined by CONFIG_FSP_TEMP_RAM_ADDR.
149	 * Enlarge the size of malloc() pool before relocation since we have
150	 * plenty of memory now.
151	 */
152	subl	$CONFIG_FSP_SYS_MALLOC_F_LEN, %esp
153	movl	%esp, GD_MALLOC_BASE(%edx)
154skip_hob:
155#else
156	/* Store table pointer */
157	movl	%esi, GD_TABLE(%edx)
158#endif
159	/* Store BIST */
160	movl	%ebp, GD_BIST(%edx)
161
162	/* Set parameter to board_init_f() to boot flags */
163	post_code(POST_START_DONE)
164	xorl	%eax, %eax
165
166	/* Enter, U-Boot! */
167	call	board_init_f
168
169	/* indicate (lack of) progress */
170	movw	$0x85, %ax
171	jmp	die
172
173.globl board_init_f_r_trampoline
174.type board_init_f_r_trampoline, @function
175board_init_f_r_trampoline:
176	/*
177	 * SDRAM has been initialised, U-Boot code has been copied into
178	 * RAM, BSS has been cleared and relocation adjustments have been
179	 * made. It is now time to jump into the in-RAM copy of U-Boot
180	 *
181	 * %eax = Address of top of new stack
182	 */
183
184	/* Stack grows down from top of SDRAM */
185	movl	%eax, %esp
186
187	/* See if we need to disable CAR */
188	call	car_uninit
189
190	/* Re-enter U-Boot by calling board_init_f_r() */
191	call	board_init_f_r
192
193die:
194	hlt
195	jmp	die
196	hlt
197
198WEAK(car_uninit)
199	ret
200ENDPROC(car_uninit)
201
202blank_idt_ptr:
203	.word	0		/* limit */
204	.long	0		/* base */
205
206	.p2align	2	/* force 4-byte alignment */
207
208	/* Add a multiboot header so U-Boot can be loaded by GRUB2 */
209multiboot_header:
210	/* magic */
211	.long	0x1badb002
212	/* flags */
213	.long	(1 << 16)
214	/* checksum */
215	.long	-0x1BADB002 - (1 << 16)
216	/* header addr */
217	.long	multiboot_header - _x86boot_start + CONFIG_SYS_TEXT_BASE
218	/* load addr */
219	.long	CONFIG_SYS_TEXT_BASE
220	/* load end addr */
221	.long	0
222	/* bss end addr */
223	.long	0
224	/* entry addr */
225	.long	CONFIG_SYS_TEXT_BASE
226
227#ifdef CONFIG_X86_LOAD_FROM_32_BIT
228	/*
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
232	 */
233gdt_ptr2:
234	.word	0x1f		/* limit (31 bytes = 4 GDT entries - 1) */
235	.long	gdt_rom2	/* base */
236
237	/* Some CPUs are picky about GDT alignment... */
238	.align	16
239.globl gdt_rom2
240gdt_rom2:
241	/*
242	 * The GDT table ...
243	 *
244	 *	 Selector	Type
245	 *	 0x00		NULL
246	 *	 0x08		Unused
247	 *	 0x10		32bit code
248	 *	 0x18		32bit data/stack
249	 */
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 */
257
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 */
265
266	/*
267	 * The Code Segment Descriptor:
268	 * - Base   = 0x00000000
269	 * - Size   = 4GB
270	 * - Access = Present, Ring 0, Exec (Code), Readable
271	 * - Flags  = 4kB Granularity, 32-bit
272	 */
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 */
279
280	/*
281	 * The Data Segment Descriptor:
282	 * - Base   = 0x00000000
283	 * - Size   = 4GB
284	 * - Access = Present, Ring 0, Non-Exec (Data), Writable
285	 * - Flags  = 4kB Granularity, 32-bit
286	 */
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 */
293#endif
294