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 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. 26 * 27 * 2. Call board_init_f(). This function prepares the hardware for 28 * execution from system RAM (DRAM, DDR...) As system RAM may not 29 * be available yet, , board_init_f() must use the current GD to 30 * store any data which must be passed on to later stages. These 31 * data include the relocation destination, the future stack, and 32 * the future GD location. 33 * 34 * (the following applies only to non-SPL builds) 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 * 4. Call relocate_code(). This function relocates U-Boot from its 41 * current location into the relocation destination computed by 42 * board_init_f(). 43 * 44 * 5. Set up final environment for calling board_init_r(). This 45 * environment has BSS (initialized to 0), initialized non-const 46 * data (initialized to their intended value), and stack in system 47 * RAM. GD has retained values set by board_init_f(). Some CPUs 48 * have some work left to do at this point regarding memory, so 49 * call c_runtime_cpu_setup. 50 * 51 * 6. Branch to board_init_r(). 52 */ 53 54/* 55 * entry point of crt0 sequence 56 */ 57 58ENTRY(_main) 59 60/* 61 * Set up initial C runtime environment and call board_init_f(0). 62 */ 63 64#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) 65 ldr sp, =(CONFIG_SPL_STACK) 66#else 67 ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) 68#endif 69 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 70 sub sp, sp, #GD_SIZE /* allocate one GD above SP */ 71 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 72 mov r9, sp /* GD is above SP */ 73 mov r0, #0 74 bl board_init_f 75 76#if ! defined(CONFIG_SPL_BUILD) 77 78/* 79 * Set up intermediate environment (new sp and gd) and call 80 * relocate_code(addr_moni). Trick here is that we'll return 81 * 'here' but relocated. 82 */ 83 84 ldr sp, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ 85 bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 86 ldr r9, [r9, #GD_BD] /* r9 = gd->bd */ 87 sub r9, r9, #GD_SIZE /* new GD is below bd */ 88 89 adr lr, here 90 ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ 91 add lr, lr, r0 92 ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */ 93 b relocate_code 94here: 95 96/* Set up final (full) environment */ 97 98 bl c_runtime_cpu_setup /* we still call old routine here */ 99 100 ldr r0, =__bss_start /* this is auto-relocated! */ 101 ldr r1, =__bss_end /* this is auto-relocated! */ 102 103 mov r2, #0x00000000 /* prepare zero to clear BSS */ 104 105clbss_l:cmp r0, r1 /* while not at end of BSS */ 106 strlo r2, [r0] /* clear 32-bit BSS word */ 107 addlo r0, r0, #4 /* move to next */ 108 blo clbss_l 109 110 bl coloured_LED_init 111 bl red_led_on 112 113 /* call board_init_r(gd_t *id, ulong dest_addr) */ 114 mov r0, r9 /* gd_t */ 115 ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ 116 /* call board_init_r */ 117 ldr pc, =board_init_r /* this is auto-relocated! */ 118 119 /* we should not return here. */ 120 121#endif 122 123ENDPROC(_main) 124