1/* 2 * crt0 - C-runtime startup Code for AArch64 U-Boot 3 * 4 * (C) Copyright 2013 5 * David Feng <fenghua@phytium.com.cn> 6 * 7 * (C) Copyright 2012 8 * Albert ARIBAUD <albert.u.boot@aribaud.net> 9 * 10 * SPDX-License-Identifier: GPL-2.0+ 11 */ 12 13#include <config.h> 14#include <asm-offsets.h> 15#include <asm/macro.h> 16#include <linux/linkage.h> 17 18/* 19 * This file handles the target-independent stages of the U-Boot 20 * start-up where a C runtime environment is needed. Its entry point 21 * is _main and is branched into from the target's start.S file. 22 * 23 * _main execution sequence is: 24 * 25 * 1. Set up initial environment for calling board_init_f(). 26 * This environment only provides a stack and a place to store 27 * the GD ('global data') structure, both located in some readily 28 * available RAM (SRAM, locked cache...). In this context, VARIABLE 29 * global data, initialized or not (BSS), are UNAVAILABLE; only 30 * CONSTANT initialized data are available. GD should be zeroed 31 * before board_init_f() is called. 32 * 33 * 2. Call board_init_f(). This function prepares the hardware for 34 * execution from system RAM (DRAM, DDR...) As system RAM may not 35 * be available yet, , board_init_f() must use the current GD to 36 * store any data which must be passed on to later stages. These 37 * data include the relocation destination, the future stack, and 38 * the future GD location. 39 * 40 * 3. Set up intermediate environment where the stack and GD are the 41 * ones allocated by board_init_f() in system RAM, but BSS and 42 * initialized non-const data are still not available. 43 * 44 * 4a.For U-Boot proper (not SPL), call relocate_code(). This function 45 * relocates U-Boot from its current location into the relocation 46 * destination computed by board_init_f(). 47 * 48 * 4b.For SPL, board_init_f() just returns (to crt0). There is no 49 * code relocation in SPL. 50 * 51 * 5. Set up final environment for calling board_init_r(). This 52 * environment has BSS (initialized to 0), initialized non-const 53 * data (initialized to their intended value), and stack in system 54 * RAM (for SPL moving the stack and GD into RAM is optional - see 55 * CONFIG_SPL_STACK_R). GD has retained values set by board_init_f(). 56 * 57 * TODO: For SPL, implement stack relocation on AArch64. 58 * 59 * 6. For U-Boot proper (not SPL), some CPUs have some work left to do 60 * at this point regarding memory, so call c_runtime_cpu_setup. 61 * 62 * 7. Branch to board_init_r(). 63 * 64 * For more information see 'Board Initialisation Flow in README. 65 */ 66 67ENTRY(_main) 68 69/* 70 * Set up initial C runtime environment and call board_init_f(0). 71 */ 72#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK) 73 ldr x0, =(CONFIG_TPL_STACK) 74#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) 75 ldr x0, =(CONFIG_SPL_STACK) 76#elif defined(CONFIG_SYS_INIT_SP_BSS_OFFSET) 77 adr x0, __bss_start 78 add x0, x0, #CONFIG_SYS_INIT_SP_BSS_OFFSET 79#else 80 ldr x0, =(CONFIG_SYS_INIT_SP_ADDR) 81#endif 82 bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ 83 mov x0, sp 84 bl board_init_f_alloc_reserve 85 mov sp, x0 86 /* set up gd here, outside any C code */ 87 mov x18, x0 88 bl board_init_f_init_reserve 89 90 mov x0, #0 91 bl board_init_f 92 93#if !defined(CONFIG_SPL_BUILD) 94/* 95 * Set up intermediate environment (new sp and gd) and call 96 * relocate_code(addr_moni). Trick here is that we'll return 97 * 'here' but relocated. 98 */ 99 ldr x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */ 100 bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ 101 ldr x18, [x18, #GD_NEW_GD] /* x18 <- gd->new_gd */ 102 103 adr lr, relocation_return 104#if CONFIG_POSITION_INDEPENDENT 105 /* Add in link-vs-runtime offset */ 106 adr x0, _start /* x0 <- Runtime value of _start */ 107 ldr x9, _TEXT_BASE /* x9 <- Linked value of _start */ 108 sub x9, x9, x0 /* x9 <- Run-vs-link offset */ 109 add lr, lr, x9 110#endif 111 /* Add in link-vs-relocation offset */ 112 ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */ 113 add lr, lr, x9 /* new return address after relocation */ 114 ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */ 115 b relocate_code 116 117relocation_return: 118 119/* 120 * Set up final (full) environment 121 */ 122 bl c_runtime_cpu_setup /* still call old routine */ 123#endif /* !CONFIG_SPL_BUILD */ 124#if defined(CONFIG_SPL_BUILD) 125 bl spl_relocate_stack_gd /* may return NULL */ 126 /* set up gd here, outside any C code, if new stack is returned */ 127 cmp x0, #0 128 csel x18, x0, x18, ne 129 /* 130 * Perform 'sp = (x0 != NULL) ? x0 : sp' while working 131 * around the constraint that conditional moves can not 132 * have 'sp' as an operand 133 */ 134 mov x1, sp 135 cmp x0, #0 136 csel x0, x0, x1, ne 137 mov sp, x0 138#endif 139 140/* 141 * Clear BSS section 142 */ 143 ldr x0, =__bss_start /* this is auto-relocated! */ 144 ldr x1, =__bss_end /* this is auto-relocated! */ 145clear_loop: 146 str xzr, [x0], #8 147 cmp x0, x1 148 b.lo clear_loop 149 150 /* call board_init_r(gd_t *id, ulong dest_addr) */ 151 mov x0, x18 /* gd_t */ 152 ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */ 153 b board_init_r /* PC relative jump */ 154 155 /* NOTREACHED - board_init_r() does not return */ 156 157ENDPROC(_main) 158