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