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. 31 * 32 * 2. Call board_init_f(). This function prepares the hardware for 33 * execution from system RAM (DRAM, DDR...) As system RAM may not 34 * be available yet, , board_init_f() must use the current GD to 35 * store any data which must be passed on to later stages. These 36 * data include the relocation destination, the future stack, and 37 * the future GD location. 38 * 39 * (the following applies only to non-SPL builds) 40 * 41 * 3. Set up intermediate environment where the stack and GD are the 42 * ones allocated by board_init_f() in system RAM, but BSS and 43 * initialized non-const data are still not available. 44 * 45 * 4. Call relocate_code(). This function relocates U-Boot from its 46 * current location into the relocation destination computed by 47 * board_init_f(). 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. GD has retained values set by board_init_f(). Some CPUs 53 * have some work left to do at this point regarding memory, so 54 * call c_runtime_cpu_setup. 55 * 56 * 6. Branch to board_init_r(). 57 */ 58 59ENTRY(_main) 60 61/* 62 * Set up initial C runtime environment and call board_init_f(0). 63 */ 64#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) 65 ldr x0, =(CONFIG_SPL_STACK) 66#else 67 ldr x0, =(CONFIG_SYS_INIT_SP_ADDR) 68#endif 69 sub x18, x0, #GD_SIZE /* allocate one GD above SP */ 70 bic x18, x18, #0x7 /* 8-byte alignment for GD */ 71zero_gd: 72 sub x0, x0, #0x8 73 str xzr, [x0] 74 cmp x0, x18 75 b.gt zero_gd 76#if defined(CONFIG_SYS_MALLOC_F_LEN) 77 sub x0, x18, #CONFIG_SYS_MALLOC_F_LEN 78 str x0, [x18, #GD_MALLOC_BASE] 79#endif 80 bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ 81 mov x0, #0 82 bl board_init_f 83 84#if !defined(CONFIG_SPL_BUILD) 85/* 86 * Set up intermediate environment (new sp and gd) and call 87 * relocate_code(addr_moni). Trick here is that we'll return 88 * 'here' but relocated. 89 */ 90 ldr x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */ 91 bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ 92 ldr x18, [x18, #GD_BD] /* x18 <- gd->bd */ 93 sub x18, x18, #GD_SIZE /* new GD is below bd */ 94 95 adr lr, relocation_return 96 ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */ 97 add lr, lr, x9 /* new return address after relocation */ 98 ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */ 99 b relocate_code 100 101relocation_return: 102 103/* 104 * Set up final (full) environment 105 */ 106 bl c_runtime_cpu_setup /* still call old routine */ 107 108/* 109 * Clear BSS section 110 */ 111 ldr x0, =__bss_start /* this is auto-relocated! */ 112 ldr x1, =__bss_end /* this is auto-relocated! */ 113 mov x2, #0 114clear_loop: 115 str x2, [x0] 116 add x0, x0, #8 117 cmp x0, x1 118 b.lo clear_loop 119 120 /* call board_init_r(gd_t *id, ulong dest_addr) */ 121 mov x0, x18 /* gd_t */ 122 ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */ 123 b board_init_r /* PC relative jump */ 124 125 /* NOTREACHED - board_init_r() does not return */ 126 127#endif /* !CONFIG_SPL_BUILD */ 128 129ENDPROC(_main) 130