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