xref: /openbmc/u-boot/arch/arm/lib/crt0.S (revision d330e04d9d427a26381b59f40875af17f4c288a2)
1 /*
2  *  crt0 - C-runtime startup Code for ARM U-Boot
3  *
4  *  Copyright (c) 2012  Albert ARIBAUD <albert.u.boot@aribaud.net>
5  *
6  * SPDX-License-Identifier:	GPL-2.0+
7  */
8 
9 #include <config.h>
10 #include <asm-offsets.h>
11 #include <linux/linkage.h>
12 #ifdef CONFIG_CPU_V7M
13 #include <asm/armv7m.h>
14 #endif
15 
16 /*
17  * This file handles the target-independent stages of the U-Boot
18  * start-up where a C runtime environment is needed. Its entry point
19  * is _main and is branched into from the target's start.S file.
20  *
21  * _main execution sequence is:
22  *
23  * 1. Set up initial environment for calling board_init_f().
24  *    This environment only provides a stack and a place to store
25  *    the GD ('global data') structure, both located in some readily
26  *    available RAM (SRAM, locked cache...). In this context, VARIABLE
27  *    global data, initialized or not (BSS), are UNAVAILABLE; only
28  *    CONSTANT initialized data are available. GD should be zeroed
29  *    before board_init_f() is called.
30  *
31  * 2. Call board_init_f(). This function prepares the hardware for
32  *    execution from system RAM (DRAM, DDR...) As system RAM may not
33  *    be available yet, , board_init_f() must use the current GD to
34  *    store any data which must be passed on to later stages. These
35  *    data include the relocation destination, the future stack, and
36  *    the future GD location.
37  *
38  * 3. Set up intermediate environment where the stack and GD are the
39  *    ones allocated by board_init_f() in system RAM, but BSS and
40  *    initialized non-const data are still not available.
41  *
42  * 4a.For U-Boot proper (not SPL), call relocate_code(). This function
43  *    relocates U-Boot from its current location into the relocation
44  *    destination computed by board_init_f().
45  *
46  * 4b.For SPL, board_init_f() just returns (to crt0). There is no
47  *    code relocation in SPL.
48  *
49  * 5. Set up final environment for calling board_init_r(). This
50  *    environment has BSS (initialized to 0), initialized non-const
51  *    data (initialized to their intended value), and stack in system
52  *    RAM (for SPL moving the stack and GD into RAM is optional - see
53  *    CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
54  *
55  * 6. For U-Boot proper (not SPL), some CPUs have some work left to do
56  *    at this point regarding memory, so call c_runtime_cpu_setup.
57  *
58  * 7. Branch to board_init_r().
59  *
60  * For more information see 'Board Initialisation Flow in README.
61  */
62 
63 /*
64  * entry point of crt0 sequence
65  */
66 
67 ENTRY(_main)
68 
69 /*
70  * Set up initial C runtime environment and call board_init_f(0).
71  */
72 
73 #if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
74 	ldr	r0, =(CONFIG_SPL_STACK)
75 #else
76 	ldr	r0, =(CONFIG_SYS_INIT_SP_ADDR)
77 #endif
78 	bic	r0, r0, #7	/* 8-byte alignment for ABI compliance */
79 	mov	sp, r0
80 	bl	board_init_f_alloc_reserve
81 	mov	sp, r0
82 	/* set up gd here, outside any C code */
83 	mov	r9, r0
84 	bl	board_init_f_init_reserve
85 
86 	mov	r0, #0
87 	bl	board_init_f
88 
89 #if ! defined(CONFIG_SPL_BUILD)
90 
91 /*
92  * Set up intermediate environment (new sp and gd) and call
93  * relocate_code(addr_moni). Trick here is that we'll return
94  * 'here' but relocated.
95  */
96 
97 	ldr	r0, [r9, #GD_START_ADDR_SP]	/* sp = gd->start_addr_sp */
98 	bic	r0, r0, #7	/* 8-byte alignment for ABI compliance */
99 	mov	sp, r0
100 	ldr	r9, [r9, #GD_BD]		/* r9 = gd->bd */
101 	sub	r9, r9, #GD_SIZE		/* new GD is below bd */
102 
103 	adr	lr, here
104 	ldr	r0, [r9, #GD_RELOC_OFF]		/* r0 = gd->reloc_off */
105 	add	lr, lr, r0
106 #if defined(CONFIG_CPU_V7M)
107 	orr	lr, #1				/* As required by Thumb-only */
108 #endif
109 	ldr	r0, [r9, #GD_RELOCADDR]		/* r0 = gd->relocaddr */
110 	b	relocate_code
111 here:
112 /*
113  * now relocate vectors
114  */
115 
116 	bl	relocate_vectors
117 
118 /* Set up final (full) environment */
119 
120 	bl	c_runtime_cpu_setup	/* we still call old routine here */
121 #endif
122 #if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
123 # ifdef CONFIG_SPL_BUILD
124 	/* Use a DRAM stack for the rest of SPL, if requested */
125 	bl	spl_relocate_stack_gd
126 	cmp	r0, #0
127 	movne	sp, r0
128 	movne	r9, r0
129 # endif
130 	ldr	r0, =__bss_start	/* this is auto-relocated! */
131 
132 #ifdef CONFIG_USE_ARCH_MEMSET
133 	ldr	r3, =__bss_end		/* this is auto-relocated! */
134 	mov	r1, #0x00000000		/* prepare zero to clear BSS */
135 
136 	subs	r2, r3, r0		/* r2 = memset len */
137 	bl	memset
138 #else
139 	ldr	r1, =__bss_end		/* this is auto-relocated! */
140 	mov	r2, #0x00000000		/* prepare zero to clear BSS */
141 
142 clbss_l:cmp	r0, r1			/* while not at end of BSS */
143 #if defined(CONFIG_CPU_V7M)
144 	itt	lo
145 #endif
146 	strlo	r2, [r0]		/* clear 32-bit BSS word */
147 	addlo	r0, r0, #4		/* move to next */
148 	blo	clbss_l
149 #endif
150 
151 #if ! defined(CONFIG_SPL_BUILD)
152 	bl coloured_LED_init
153 	bl red_led_on
154 #endif
155 	/* call board_init_r(gd_t *id, ulong dest_addr) */
156 	mov     r0, r9                  /* gd_t */
157 	ldr	r1, [r9, #GD_RELOCADDR]	/* dest_addr */
158 	/* call board_init_r */
159 #if CONFIG_IS_ENABLED(SYS_THUMB_BUILD)
160 	ldr	lr, =board_init_r	/* this is auto-relocated! */
161 	bx	lr
162 #else
163 	ldr	pc, =board_init_r	/* this is auto-relocated! */
164 #endif
165 	/* we should not return here. */
166 #endif
167 
168 ENDPROC(_main)
169