2 * crt0 - C-runtime startup Code for ARM U-Boot
4 * Copyright (c) 2012 Albert ARIBAUD <albert.u.boot@aribaud.net>
6 * SPDX-License-Identifier: GPL-2.0+
10 #include <asm-offsets.h>
11 #include <linux/linkage.h>
13 #include <asm/armv7m.h>
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.
21 * _main execution sequence is:
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.
30 * 2. Call board_init_f(). This function prepares the hardware for
31 * execution from system RAM (DRAM, DDR...) As system RAM may not
32 * be available yet, , board_init_f() must use the current GD to
33 * store any data which must be passed on to later stages. These
34 * data include the relocation destination, the future stack, and
35 * the future GD location.
37 * (the following applies only to non-SPL builds)
39 * 3. Set up intermediate environment where the stack and GD are the
40 * ones allocated by board_init_f() in system RAM, but BSS and
41 * initialized non-const data are still not available.
43 * 4. Call relocate_code(). This function relocates U-Boot from its
44 * current location into the relocation destination computed by
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. GD has retained values set by board_init_f(). Some CPUs
51 * have some work left to do at this point regarding memory, so
52 * call c_runtime_cpu_setup.
54 * 6. Branch to board_init_r().
58 * entry point of crt0 sequence
64 * Set up initial C runtime environment and call board_init_f(0).
67 #if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
68 ldr sp, =(CONFIG_SPL_STACK)
70 ldr sp, =(CONFIG_SYS_INIT_SP_ADDR)
72 #if defined(CONFIG_CPU_V7M) /* v7M forbids using SP as BIC destination */
77 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
80 sub sp, sp, #GD_SIZE /* allocate one GD above SP */
81 #if defined(CONFIG_CPU_V7M) /* v7M forbids using SP as BIC destination */
86 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
88 mov r9, sp /* GD is above SP */
92 cmp r1, r2 /* while not at end of GD */
93 #if defined(CONFIG_CPU_V7M)
96 strlo r0, [r1] /* clear 32-bit GD word */
97 addlo r1, r1, #4 /* move to next */
99 #if defined(CONFIG_SYS_MALLOC_F_LEN)
100 sub sp, sp, #CONFIG_SYS_MALLOC_F_LEN
101 str sp, [r9, #GD_MALLOC_BASE]
103 /* mov r0, #0 not needed due to above code */
106 #if ! defined(CONFIG_SPL_BUILD)
109 * Set up intermediate environment (new sp and gd) and call
110 * relocate_code(addr_moni). Trick here is that we'll return
111 * 'here' but relocated.
114 ldr sp, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */
115 #if defined(CONFIG_CPU_V7M) /* v7M forbids using SP as BIC destination */
120 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */
122 ldr r9, [r9, #GD_BD] /* r9 = gd->bd */
123 sub r9, r9, #GD_SIZE /* new GD is below bd */
126 ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */
128 #if defined(CONFIG_CPU_V7M)
129 orr lr, #1 /* As required by Thumb-only */
131 ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
135 * now relocate vectors
140 /* Set up final (full) environment */
142 bl c_runtime_cpu_setup /* we still call old routine here */
144 #if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK)
145 # ifdef CONFIG_SPL_BUILD
146 /* Use a DRAM stack for the rest of SPL, if requested */
147 bl spl_relocate_stack_gd
151 ldr r0, =__bss_start /* this is auto-relocated! */
153 #ifdef CONFIG_USE_ARCH_MEMSET
154 ldr r3, =__bss_end /* this is auto-relocated! */
155 mov r1, #0x00000000 /* prepare zero to clear BSS */
157 subs r2, r3, r0 /* r2 = memset len */
160 ldr r1, =__bss_end /* this is auto-relocated! */
161 mov r2, #0x00000000 /* prepare zero to clear BSS */
163 clbss_l:cmp r0, r1 /* while not at end of BSS */
164 #if defined(CONFIG_CPU_V7M)
167 strlo r2, [r0] /* clear 32-bit BSS word */
168 addlo r0, r0, #4 /* move to next */
172 #if ! defined(CONFIG_SPL_BUILD)
176 /* call board_init_r(gd_t *id, ulong dest_addr) */
177 mov r0, r9 /* gd_t */
178 ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */
179 /* call board_init_r */
180 ldr pc, =board_init_r /* this is auto-relocated! */
182 /* we should not return here. */