diff options
Diffstat (limited to 'arch/arm/lib/crt0_64.S')
| -rw-r--r-- | arch/arm/lib/crt0_64.S | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/arch/arm/lib/crt0_64.S b/arch/arm/lib/crt0_64.S new file mode 100644 index 000000000..77563967e --- /dev/null +++ b/arch/arm/lib/crt0_64.S @@ -0,0 +1,113 @@ +/* + * crt0 - C-runtime startup Code for AArch64 U-Boot + * + * (C) Copyright 2013 + * David Feng <fenghua@phytium.com.cn> + * + * (C) Copyright 2012 + * Albert ARIBAUD <albert.u.boot@aribaud.net> + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <config.h> +#include <asm-offsets.h> +#include <asm/macro.h> +#include <linux/linkage.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. + * + * 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. + * + * (the following applies only to non-SPL builds) + * + * 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. + * + * 4. Call relocate_code(). This function relocates U-Boot from its + * current location into the relocation destination computed by + * board_init_f(). + * + * 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. GD has retained values set by board_init_f(). Some CPUs + * have some work left to do at this point regarding memory, so + * call c_runtime_cpu_setup. + * + * 6. Branch to board_init_r(). + */ + +ENTRY(_main) + +/* + * Set up initial C runtime environment and call board_init_f(0). + */ + ldr x0, =(CONFIG_SYS_INIT_SP_ADDR) + sub x0, x0, #GD_SIZE /* allocate one GD above SP */ + bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ + mov x18, sp /* GD is above SP */ + mov x0, #0 + bl board_init_f + +/* + * 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 x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */ + bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */ + ldr x18, [x18, #GD_BD] /* x18 <- gd->bd */ + sub x18, x18, #GD_SIZE /* new GD is below bd */ + + adr lr, relocation_return + ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */ + add lr, lr, x9 /* new return address after relocation */ + ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */ + b relocate_code + +relocation_return: + +/* + * Set up final (full) environment + */ + bl c_runtime_cpu_setup /* still call old routine */ + +/* + * Clear BSS section + */ + ldr x0, =__bss_start /* this is auto-relocated! */ + ldr x1, =__bss_end /* this is auto-relocated! */ + mov x2, #0 +clear_loop: + str x2, [x0] + add x0, x0, #8 + cmp x0, x1 + b.lo clear_loop + + /* call board_init_r(gd_t *id, ulong dest_addr) */ + mov x0, x18 /* gd_t */ + ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */ + b board_init_r /* PC relative jump */ + + /* NOTREACHED - board_init_r() does not return */ + +ENDPROC(_main) |