/* SPDX-License-Identifier: GPL-2.0+ */ /* * crt0 - C-runtime startup Code for ARM U-Boot * * Copyright (c) 2012 Albert ARIBAUD <albert.u.boot@aribaud.net> */ #include <config.h> #include <asm-offsets.h> #include <linux/linkage.h> #include <asm/assembler.h> /* * This file handles the target-independent stages of the U-Boot * start-up where a C runtime environment is needed. Its entry point * is _main and is branched into from the target's start.S file. * * _main execution sequence is: * * 1. Set up initial environment for calling board_init_f(). * This environment only provides a stack and a place to store * the GD ('global data') structure, both located in some readily * available RAM (SRAM, locked cache...). In this context, VARIABLE * global data, initialized or not (BSS), are UNAVAILABLE; only * CONSTANT initialized data are available. GD should be zeroed * before board_init_f() is called. * * 2. Call board_init_f(). This function prepares the hardware for * execution from system RAM (DRAM, DDR...) As system RAM may not * be available yet, , board_init_f() must use the current GD to * store any data which must be passed on to later stages. These * data include the relocation destination, the future stack, and * the future GD location. * * 3. Set up intermediate environment where the stack and GD are the * ones allocated by board_init_f() in system RAM, but BSS and * initialized non-const data are still not available. * * 4a.For U-Boot proper (not SPL), call relocate_code(). This function * relocates U-Boot from its current location into the relocation * destination computed by board_init_f(). * * 4b.For SPL, board_init_f() just returns (to crt0). There is no * code relocation in SPL. * * 5. Set up final environment for calling board_init_r(). This * environment has BSS (initialized to 0), initialized non-const * data (initialized to their intended value), and stack in system * RAM (for SPL moving the stack and GD into RAM is optional - see * CONFIG_SPL_STACK_R). GD has retained values set by board_init_f(). * * 6. For U-Boot proper (not SPL), some CPUs have some work left to do * at this point regarding memory, so call c_runtime_cpu_setup. * * 7. Branch to board_init_r(). * * For more information see 'Board Initialisation Flow in README. */ /* * Macro for clearing BSS during SPL execution. Usually called during the * relocation process for most boards before entering board_init_r(), but * can also be done early before entering board_init_f() on plaforms that * can afford it due to sufficient memory being available early. */ .macro CLEAR_BSS ldr r0, =__bss_start /* this is auto-relocated! */ #ifdef CONFIG_USE_ARCH_MEMSET ldr r3, =__bss_end /* this is auto-relocated! */ mov r1, #0x00000000 /* prepare zero to clear BSS */ subs r2, r3, r0 /* r2 = memset len */ bl memset #else ldr r1, =__bss_end /* this is auto-relocated! */ mov r2, #0x00000000 /* prepare zero to clear BSS */ clbss_l:cmp r0, r1 /* while not at end of BSS */ strlo r2, [r0] /* clear 32-bit BSS word */ addlo r0, r0, #4 /* move to next */ blo clbss_l #endif .endm /* * entry point of crt0 sequence */ ENTRY(_main) /* * Set up initial C runtime environment and call board_init_f(0). */ #if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK) ldr r0, =(CONFIG_TPL_STACK) #elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK) ldr r0, =(CONFIG_SPL_STACK) #else ldr r0, =(CONFIG_SYS_INIT_SP_ADDR) #endif bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ mov sp, r0 bl board_init_f_alloc_reserve mov sp, r0 /* set up gd here, outside any C code */ mov r9, r0 bl board_init_f_init_reserve #if defined(CONFIG_DEBUG_UART) && CONFIG_IS_ENABLED(SERIAL) bl debug_uart_init #endif #if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_EARLY_BSS) CLEAR_BSS #endif mov r0, #0 bl board_init_f #if ! defined(CONFIG_SPL_BUILD) /* * Set up intermediate environment (new sp and gd) and call * relocate_code(addr_moni). Trick here is that we'll return * 'here' but relocated. */ ldr r0, [r9, #GD_START_ADDR_SP] /* sp = gd->start_addr_sp */ bic r0, r0, #7 /* 8-byte alignment for ABI compliance */ mov sp, r0 ldr r9, [r9, #GD_NEW_GD] /* r9 <- gd->new_gd */ adr lr, here #if defined(CONFIG_POSITION_INDEPENDENT) adr r0, _main ldr r1, _start_ofs add r0, r1 ldr r1, =CONFIG_SYS_TEXT_BASE sub r1, r0 add lr, r1 #endif ldr r0, [r9, #GD_RELOC_OFF] /* r0 = gd->reloc_off */ add lr, lr, r0 #if defined(CONFIG_CPU_V7M) orr lr, #1 /* As required by Thumb-only */ #endif ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */ b relocate_code here: /* * now relocate vectors */ bl relocate_vectors /* Set up final (full) environment */ bl c_runtime_cpu_setup /* we still call old routine here */ #endif #if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK) #if !defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SPL_EARLY_BSS) CLEAR_BSS #endif # ifdef CONFIG_SPL_BUILD /* Use a DRAM stack for the rest of SPL, if requested */ bl spl_relocate_stack_gd cmp r0, #0 movne sp, r0 movne r9, r0 # endif #if ! defined(CONFIG_SPL_BUILD) bl coloured_LED_init bl red_led_on #endif /* call board_init_r(gd_t *id, ulong dest_addr) */ mov r0, r9 /* gd_t */ ldr r1, [r9, #GD_RELOCADDR] /* dest_addr */ /* call board_init_r */ #if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) ldr lr, =board_init_r /* this is auto-relocated! */ bx lr #else ldr pc, =board_init_r /* this is auto-relocated! */ #endif /* we should not return here. */ #endif ENDPROC(_main) _start_ofs: .word _start - _main