LXR uboot/arch/arm/lib/crt0

   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_SPL_BUILD) && defined(CONFIG_SPL_STACK)
  73        ldr     x0, =(CONFIG_SPL_STACK)
  74#else
  75        ldr     x0, =(CONFIG_SYS_INIT_SP_ADDR)
  76#endif
  77        bic     sp, x0, #0xf    /* 16-byte alignment for ABI compliance */
  78        mov     x0, sp
  79        bl      board_init_f_alloc_reserve
  80        mov     sp, x0
  81        /* set up gd here, outside any C code */
  82        mov     x18, x0
  83        bl      board_init_f_init_reserve
  84
  85        mov     x0, #0
  86        bl      board_init_f
  87
  88#if !defined(CONFIG_SPL_BUILD)
  89/*
  90 * Set up intermediate environment (new sp and gd) and call
  91 * relocate_code(addr_moni). Trick here is that we'll return
  92 * 'here' but relocated.
  93 */
  94        ldr     x0, [x18, #GD_START_ADDR_SP]    /* x0 <- gd->start_addr_sp */
  95        bic     sp, x0, #0xf    /* 16-byte alignment for ABI compliance */
  96        ldr     x18, [x18, #GD_BD]              /* x18 <- gd->bd */
  97        sub     x18, x18, #GD_SIZE              /* new GD is below bd */
  98
  99        adr     lr, relocation_return
 100        ldr     x9, [x18, #GD_RELOC_OFF]        /* x9 <- gd->reloc_off */
 101        add     lr, lr, x9      /* new return address after relocation */
 102        ldr     x0, [x18, #GD_RELOCADDR]        /* x0 <- gd->relocaddr */
 103        b       relocate_code
 104
 105relocation_return:
 106
 107/*
 108 * Set up final (full) environment
 109 */
 110        bl      c_runtime_cpu_setup             /* still call old routine */
 111#endif /* !CONFIG_SPL_BUILD */
 112
 113/* TODO: For SPL, call spl_relocate_stack_gd() to alloc stack relocation */
 114
 115/*
 116 * Clear BSS section
 117 */
 118        ldr     x0, =__bss_start                /* this is auto-relocated! */
 119        ldr     x1, =__bss_end                  /* this is auto-relocated! */
 120        mov     x2, #0
 121clear_loop:
 122        str     x2, [x0]
 123        add     x0, x0, #8
 124        cmp     x0, x1
 125        b.lo    clear_loop
 126
 127        /* call board_init_r(gd_t *id, ulong dest_addr) */
 128        mov     x0, x18                         /* gd_t */
 129        ldr     x1, [x18, #GD_RELOCADDR]        /* dest_addr */
 130        b       board_init_r                    /* PC relative jump */
 131
 132        /* NOTREACHED - board_init_r() does not return */
 133
 134ENDPROC(_main)
 135