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