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 67ENTRY(_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 sp, =(CONFIG_SPL_STACK) 75#else 76 ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) 77#endif 78#if defined(CONFIG_CPU_V7M) /* v7M forbids using SP as BIC destination */ 79 mov r3, sp 80 bic r3, r3, #7 81 mov sp, r3 82#else 83 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 84#endif 85 mov r0, sp 86 bl board_init_f_alloc_reserve 87 mov sp, r0 88 /* set up gd here, outside any C code */ 89 mov r9, r0 90 bl board_init_f_init_reserve 91 92 mov r0, #0 93 bl board_init_f 94 95#if ! defined(CONFIG_SPL_BUILD) 96 97/* 98 * Set up intermediate environment (new sp and gd) and call 99 * relocate_code(addr_moni). Trick here is that we'll return 100 * 'here' but relocated. 101 */ 102 103 ldr sp, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ 104#if defined(CONFIG_CPU_V7M) /* v7M forbids using SP as BIC destination */ 105 mov r3, sp 106 bic r3, r3, #7 107 mov sp, r3 108#else 109 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 110#endif 111 ldr r9, [r9, #GD_BD] /* r9 = gd->bd */ 112 sub r9, r9, #GD_SIZE /* new GD is below bd */ 113 114 adr lr, here 115 ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ 116 add lr, lr, r0 117#if defined(CONFIG_CPU_V7M) 118 orr lr, #1 /* As required by Thumb-only */ 119#endif 120 ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */ 121 b relocate_code 122here: 123/* 124 * now relocate vectors 125 */ 126 127 bl relocate_vectors 128 129/* Set up final (full) environment */ 130 131 bl c_runtime_cpu_setup /* we still call old routine here */ 132#endif 133#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK) 134# ifdef CONFIG_SPL_BUILD 135 /* Use a DRAM stack for the rest of SPL, if requested */ 136 bl spl_relocate_stack_gd 137 cmp r0, #0 138 movne sp, r0 139 movne r9, r0 140# endif 141 ldr r0, =__bss_start /* this is auto-relocated! */ 142 143#ifdef CONFIG_USE_ARCH_MEMSET 144 ldr r3, =__bss_end /* this is auto-relocated! */ 145 mov r1, #0x00000000 /* prepare zero to clear BSS */ 146 147 subs r2, r3, r0 /* r2 = memset len */ 148 bl memset 149#else 150 ldr r1, =__bss_end /* this is auto-relocated! */ 151 mov r2, #0x00000000 /* prepare zero to clear BSS */ 152 153clbss_l:cmp r0, r1 /* while not at end of BSS */ 154#if defined(CONFIG_CPU_V7M) 155 itt lo 156#endif 157 strlo r2, [r0] /* clear 32-bit BSS word */ 158 addlo r0, r0, #4 /* move to next */ 159 blo clbss_l 160#endif 161 162#if ! defined(CONFIG_SPL_BUILD) 163 bl coloured_LED_init 164 bl red_led_on 165#endif 166 /* call board_init_r(gd_t *id, ulong dest_addr) */ 167 mov r0, r9 /* gd_t */ 168 ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ 169 /* call board_init_r */ 170 ldr pc, =board_init_r /* this is auto-relocated! */ 171 172 /* we should not return here. */ 173#endif 174 175ENDPROC(_main) 176