1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 *  crt0 - C-runtime startup Code for ARM U-Boot
4 *
5 *  Copyright (c) 2012  Albert ARIBAUD <albert.u.boot@aribaud.net>
6 */
7
8#include <config.h>
9#include <asm-offsets.h>
10#include <linux/linkage.h>
11#include <asm/assembler.h>
12#include <system-constants.h>
13
14/*
15 * This file handles the target-independent stages of the U-Boot
16 * start-up where a C runtime environment is needed. Its entry point
17 * is _main and is branched into from the target's start.S file.
18 *
19 * _main execution sequence is:
20 *
21 * 1. Set up initial environment for calling board_init_f().
22 *    This environment only provides a stack and a place to store
23 *    the GD ('global data') structure, both located in some readily
24 *    available RAM (SRAM, locked cache...). In this context, VARIABLE
25 *    global data, initialized or not (BSS), are UNAVAILABLE; only
26 *    CONSTANT initialized data are available. GD should be zeroed
27 *    before board_init_f() is called.
28 *
29 * 2. Call board_init_f(). This function prepares the hardware for
30 *    execution from system RAM (DRAM, DDR...) As system RAM may not
31 *    be available yet, , board_init_f() must use the current GD to
32 *    store any data which must be passed on to later stages. These
33 *    data include the relocation destination, the future stack, and
34 *    the future GD location.
35 *
36 * 3. Set up intermediate environment where the stack and GD are the
37 *    ones allocated by board_init_f() in system RAM, but BSS and
38 *    initialized non-const data are still not available.
39 *
40 * 4a.For U-Boot proper (not SPL), call relocate_code(). This function
41 *    relocates U-Boot from its current location into the relocation
42 *    destination computed by board_init_f().
43 *
44 * 4b.For SPL, board_init_f() just returns (to crt0). There is no
45 *    code relocation in SPL.
46 *
47 * 5. Set up final environment for calling board_init_r(). This
48 *    environment has BSS (initialized to 0), initialized non-const
49 *    data (initialized to their intended value), and stack in system
50 *    RAM (for SPL moving the stack and GD into RAM is optional - see
51 *    CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
52 *
53 * 6. For U-Boot proper (not SPL), some CPUs have some work left to do
54 *    at this point regarding memory, so call c_runtime_cpu_setup.
55 *
56 * 7. Branch to board_init_r().
57 *
58 * For more information see 'Board Initialisation Flow in README.
59 */
60
61/*
62 * Macro for clearing BSS during SPL execution. Usually called during the
63 * relocation process for most boards before entering board_init_r(), but
64 * can also be done early before entering board_init_f() on plaforms that
65 * can afford it due to sufficient memory being available early.
66 */
67
68.macro CLEAR_BSS
69	ldr	r0, =__bss_start	/* this is auto-relocated! */
70
71#ifdef CONFIG_USE_ARCH_MEMSET
72	ldr	r3, =__bss_end		/* this is auto-relocated! */
73	mov	r1, #0x00000000		/* prepare zero to clear BSS */
74
75	subs	r2, r3, r0		/* r2 = memset len */
76	bl	memset
77#else
78	ldr	r1, =__bss_end		/* this is auto-relocated! */
79	mov	r2, #0x00000000		/* prepare zero to clear BSS */
80
81clbss_l:cmp	r0, r1			/* while not at end of BSS */
82	strlo	r2, [r0]		/* clear 32-bit BSS word */
83	addlo	r0, r0, #4		/* move to next */
84	blo	clbss_l
85#endif
86.endm
87
88/*
89 * entry point of crt0 sequence
90 */
91
92ENTRY(_main)
93
94/* Call arch_very_early_init before initializing C runtime environment. */
95#if CONFIG_IS_ENABLED(ARCH_VERY_EARLY_INIT)
96	bl	arch_very_early_init
97#endif
98
99/*
100 * Set up initial C runtime environment and call board_init_f(0).
101 */
102
103#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK)
104	ldr	r0, =(CONFIG_TPL_STACK)
105#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
106	ldr	r0, =(CONFIG_SPL_STACK)
107#else
108	ldr	r0, =(SYS_INIT_SP_ADDR)
109#endif
110	bic	r0, r0, #7	/* 8-byte alignment for ABI compliance */
111	mov	sp, r0
112	bl	board_init_f_alloc_reserve
113	mov	sp, r0
114	/* set up gd here, outside any C code */
115	mov	r9, r0
116	bl	board_init_f_init_reserve
117
118#if defined(CONFIG_DEBUG_UART) && CONFIG_IS_ENABLED(SERIAL)
119	bl	debug_uart_init
120#endif
121
122#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_EARLY_BSS)
123	CLEAR_BSS
124#endif
125
126	mov	r0, #0
127	bl	board_init_f
128
129#if ! defined(CONFIG_SPL_BUILD)
130
131/*
132 * Set up intermediate environment (new sp and gd) and call
133 * relocate_code(addr_moni). Trick here is that we'll return
134 * 'here' but relocated.
135 */
136
137	ldr	r0, [r9, #GD_START_ADDR_SP]	/* sp = gd->start_addr_sp */
138	bic	r0, r0, #7	/* 8-byte alignment for ABI compliance */
139	mov	sp, r0
140	ldr	r9, [r9, #GD_NEW_GD]		/* r9 <- gd->new_gd */
141
142	adr	lr, here
143#if defined(CONFIG_POSITION_INDEPENDENT)
144	adr	r0, _main
145	ldr	r1, _start_ofs
146	add	r0, r1
147	ldr	r1, =CONFIG_TEXT_BASE
148	sub	r1, r0
149	add	lr, r1
150#if defined(CONFIG_SYS_RELOC_GD_ENV_ADDR)
151	ldr	r0, [r9, #GD_ENV_ADDR]		/* r0 = gd->env_addr */
152	add	r0, r0, r1
153	str	r0, [r9, #GD_ENV_ADDR]
154#endif
155#endif
156	ldr	r0, [r9, #GD_RELOC_OFF]		/* r0 = gd->reloc_off */
157	add	lr, lr, r0
158#if defined(CONFIG_CPU_V7M)
159	orr	lr, #1				/* As required by Thumb-only */
160#endif
161	ldr	r0, [r9, #GD_RELOCADDR]		/* r0 = gd->relocaddr */
162	b	relocate_code
163here:
164/*
165 * now relocate vectors
166 */
167
168	bl	relocate_vectors
169
170/* Set up final (full) environment */
171
172	bl	c_runtime_cpu_setup	/* we still call old routine here */
173#endif
174#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK)
175
176#if !defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_EARLY_BSS)
177	CLEAR_BSS
178#endif
179
180# ifdef CONFIG_SPL_BUILD
181	/* Use a DRAM stack for the rest of SPL, if requested */
182	bl	spl_relocate_stack_gd
183	cmp	r0, #0
184	movne	sp, r0
185	movne	r9, r0
186# endif
187
188#if ! defined(CONFIG_SPL_BUILD)
189	bl coloured_LED_init
190	bl red_led_on
191#endif
192	/* call board_init_r(gd_t *id, ulong dest_addr) */
193	mov     r0, r9                  /* gd_t */
194	ldr	r1, [r9, #GD_RELOCADDR]	/* dest_addr */
195	/* call board_init_r */
196#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD)
197	ldr	lr, =board_init_r	/* this is auto-relocated! */
198	bx	lr
199#else
200	ldr	pc, =board_init_r	/* this is auto-relocated! */
201#endif
202	/* we should not return here. */
203#endif
204
205ENDPROC(_main)
206
207_start_ofs:
208	.word	_start - _main
209