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#ifdef CONFIG_CPU_V7M 12#include <asm/armv7m.h> 13#endif 14 15/* 16 * This file handles the target-independent stages of the U-Boot 17 * start-up where a C runtime environment is needed. Its entry point 18 * is _main and is branched into from the target's start.S file. 19 * 20 * _main execution sequence is: 21 * 22 * 1. Set up initial environment for calling board_init_f(). 23 * This environment only provides a stack and a place to store 24 * the GD ('global data') structure, both located in some readily 25 * available RAM (SRAM, locked cache...). In this context, VARIABLE 26 * global data, initialized or not (BSS), are UNAVAILABLE; only 27 * CONSTANT initialized data are available. GD should be zeroed 28 * before board_init_f() is called. 29 * 30 * 2. Call board_init_f(). This function prepares the hardware for 31 * execution from system RAM (DRAM, DDR...) As system RAM may not 32 * be available yet, , board_init_f() must use the current GD to 33 * store any data which must be passed on to later stages. These 34 * data include the relocation destination, the future stack, and 35 * the future GD location. 36 * 37 * 3. Set up intermediate environment where the stack and GD are the 38 * ones allocated by board_init_f() in system RAM, but BSS and 39 * initialized non-const data are still not available. 40 * 41 * 4a.For U-Boot proper (not SPL), call relocate_code(). This function 42 * relocates U-Boot from its current location into the relocation 43 * destination computed by board_init_f(). 44 * 45 * 4b.For SPL, board_init_f() just returns (to crt0). There is no 46 * code relocation in SPL. 47 * 48 * 5. Set up final environment for calling board_init_r(). This 49 * environment has BSS (initialized to 0), initialized non-const 50 * data (initialized to their intended value), and stack in system 51 * RAM (for SPL moving the stack and GD into RAM is optional - see 52 * CONFIG_SPL_STACK_R). GD has retained values set by board_init_f(). 53 * 54 * 6. For U-Boot proper (not SPL), some CPUs have some work left to do 55 * at this point regarding memory, so call c_runtime_cpu_setup. 56 * 57 * 7. Branch to board_init_r(). 58 * 59 * For more information see 'Board Initialisation Flow in README. 60 */ 61 62/* 63 * entry point of crt0 sequence 64 */ 65 66ENTRY(_main) 67 68/* 69 * Set up initial C runtime environment and call board_init_f(0). 70 */ 71 72#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) 73 ldr r0, =(CONFIG_SPL_STACK) 74#else 75 ldr r0, =(CONFIG_SYS_INIT_SP_ADDR) 76#endif 77 bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ 78 mov sp, r0 79 bl board_init_f_alloc_reserve 80 mov sp, r0 81 /* set up gd here, outside any C code */ 82 mov r9, r0 83 bl board_init_f_init_reserve 84 85 mov r0, #0 86 bl board_init_f 87 88#if ! defined(CONFIG_SPL_BUILD) 89 90/* 91 * Set up intermediate environment (new sp and gd) and call 92 * relocate_code(addr_moni). Trick here is that we'll return 93 * 'here' but relocated. 94 */ 95 96 ldr r0, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ 97 bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ 98 mov sp, r0 99 ldr r9, [r9, #GD_BD] /* r9 = gd->bd */ 100 sub r9, r9, #GD_SIZE /* new GD is below bd */ 101 102 adr lr, here 103 ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ 104 add lr, lr, r0 105#if defined(CONFIG_CPU_V7M) 106 orr lr, #1 /* As required by Thumb-only */ 107#endif 108 ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */ 109 b relocate_code 110here: 111/* 112 * now relocate vectors 113 */ 114 115 bl relocate_vectors 116 117/* Set up final (full) environment */ 118 119 bl c_runtime_cpu_setup /* we still call old routine here */ 120#endif 121#if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK) 122# ifdef CONFIG_SPL_BUILD 123 /* Use a DRAM stack for the rest of SPL, if requested */ 124 bl spl_relocate_stack_gd 125 cmp r0, #0 126 movne sp, r0 127 movne r9, r0 128# endif 129 ldr r0, =__bss_start /* this is auto-relocated! */ 130 131#ifdef CONFIG_USE_ARCH_MEMSET 132 ldr r3, =__bss_end /* this is auto-relocated! */ 133 mov r1, #0x00000000 /* prepare zero to clear BSS */ 134 135 subs r2, r3, r0 /* r2 = memset len */ 136 bl memset 137#else 138 ldr r1, =__bss_end /* this is auto-relocated! */ 139 mov r2, #0x00000000 /* prepare zero to clear BSS */ 140 141clbss_l:cmp r0, r1 /* while not at end of BSS */ 142#if defined(CONFIG_CPU_V7M) 143 itt lo 144#endif 145 strlo r2, [r0] /* clear 32-bit BSS word */ 146 addlo r0, r0, #4 /* move to next */ 147 blo clbss_l 148#endif 149 150#if ! defined(CONFIG_SPL_BUILD) 151 bl coloured_LED_init 152 bl red_led_on 153#endif 154 /* call board_init_r(gd_t *id, ulong dest_addr) */ 155 mov r0, r9 /* gd_t */ 156 ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ 157 /* call board_init_r */ 158#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) 159 ldr lr, =board_init_r /* this is auto-relocated! */ 160 bx lr 161#else 162 ldr pc, =board_init_r /* this is auto-relocated! */ 163#endif 164 /* we should not return here. */ 165#endif 166 167ENDPROC(_main) 168