arch/arm/lib/crt0_64.S

   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@phytium.com.cn>
   7  *
   8  * (C) Copyright 2012
   9  * Albert ARIBAUD <albert.u.boot@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)