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 * Macro for clearing BSS during SPL execution. Usually called during the 62 * relocation process for most boards before entering board_init_r(), but 63 * can also be done early before entering board_init_f() on plaforms that 64 * can afford it due to sufficient memory being available early. 65 */ 66 67.macro SPL_CLEAR_BSS 68 ldr r0, =__bss_start /* this is auto-relocated! */ 69 70#ifdef CONFIG_USE_ARCH_MEMSET 71 ldr r3, =__bss_end /* this is auto-relocated! */ 72 mov r1, #0x00000000 /* prepare zero to clear BSS */ 73 74 subs r2, r3, r0 /* r2 = memset len */ 75 bl memset 76#else 77 ldr r1, =__bss_end /* this is auto-relocated! */ 78 mov r2, #0x00000000 /* prepare zero to clear BSS */ 79 80clbss_l:cmp r0, r1 /* while not at end of BSS */ 81 strlo r2, [r0] /* clear 32-bit BSS word */ 82 addlo r0, r0, #4 /* move to next */ 83 blo clbss_l 84#endif 85.endm 86 87/* 88 * entry point of crt0 sequence 89 */ 90 91ENTRY(_main) 92 93/* 94 * Set up initial C runtime environment and call board_init_f(0). 95 */ 96 97#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK) 98 ldr r0, =(CONFIG_TPL_STACK) 99#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) 100 ldr r0, =(CONFIG_SPL_STACK) 101#else 102 ldr r0, =(CONFIG_SYS_INIT_SP_ADDR) 103#endif 104 bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ 105 mov sp, r0 106 bl board_init_f_alloc_reserve 107 mov sp, r0 108 /* set up gd here, outside any C code */ 109 mov r9, r0 110 bl board_init_f_init_reserve 111 112#if defined(CONFIG_SPL_EARLY_BSS) 113 SPL_CLEAR_BSS 114#endif 115 116 mov r0, #0 117 bl board_init_f 118 119#if ! defined(CONFIG_SPL_BUILD) 120 121/* 122 * Set up intermediate environment (new sp and gd) and call 123 * relocate_code(addr_moni). Trick here is that we'll return 124 * 'here' but relocated. 125 */ 126 127 ldr r0, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ 128 bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ 129 mov sp, r0 130 ldr r9, [r9, #GD_BD] /* r9 = gd->bd */ 131 sub r9, r9, #GD_SIZE /* new GD is below bd */ 132 133 adr lr, here 134 ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ 135 add lr, lr, r0 136#if defined(CONFIG_CPU_V7M) 137 orr lr, #1 /* As required by Thumb-only */ 138#endif 139 ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */ 140 b relocate_code 141here: 142/* 143 * now relocate vectors 144 */ 145 146 bl relocate_vectors 147 148/* Set up final (full) environment */ 149 150 bl c_runtime_cpu_setup /* we still call old routine here */ 151#endif 152#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK) 153 154#if !defined(CONFIG_SPL_EARLY_BSS) 155 SPL_CLEAR_BSS 156#endif 157 158# ifdef CONFIG_SPL_BUILD 159 /* Use a DRAM stack for the rest of SPL, if requested */ 160 bl spl_relocate_stack_gd 161 cmp r0, #0 162 movne sp, r0 163 movne r9, r0 164# endif 165 166#if ! defined(CONFIG_SPL_BUILD) 167 bl coloured_LED_init 168 bl red_led_on 169#endif 170 /* call board_init_r(gd_t *id, ulong dest_addr) */ 171 mov r0, r9 /* gd_t */ 172 ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ 173 /* call board_init_r */ 174#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) 175 ldr lr, =board_init_r /* this is auto-relocated! */ 176 bx lr 177#else 178 ldr pc, =board_init_r /* this is auto-relocated! */ 179#endif 180 /* we should not return here. */ 181#endif 182 183ENDPROC(_main) 184