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