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
66ENTRY(_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_INIT_SP_RELATIVE)
76#if CONFIG_POSITION_INDEPENDENT
77	adrp	x0, __bss_start     /* x0 <- Runtime &__bss_start */
78	add	x0, x0, #:lo12:__bss_start
79#else
80	adr	x0, __bss_start
81#endif
82	add	x0, x0, #CONFIG_SYS_INIT_SP_BSS_OFFSET
83#else
84	ldr	x0, =(CONFIG_SYS_INIT_SP_ADDR)
85#endif
86	bic	sp, x0, #0xf	/* 16-byte alignment for ABI compliance */
87	mov	x0, sp
88	bl	board_init_f_alloc_reserve
89	mov	sp, x0
90	/* set up gd here, outside any C code */
91	mov	x18, x0
92	bl	board_init_f_init_reserve
93
94	mov	x0, #0
95	bl	board_init_f
96
97#if !defined(CONFIG_SPL_BUILD)
98/*
99 * Set up intermediate environment (new sp and gd) and call
100 * relocate_code(addr_moni). Trick here is that we'll return
101 * 'here' but relocated.
102 */
103	ldr	x0, [x18, #GD_START_ADDR_SP]	/* x0 <- gd->start_addr_sp */
104	bic	sp, x0, #0xf	/* 16-byte alignment for ABI compliance */
105	ldr	x18, [x18, #GD_NEW_GD]		/* x18 <- gd->new_gd */
106
107	adr	lr, relocation_return
108#if CONFIG_POSITION_INDEPENDENT
109	/* Add in link-vs-runtime offset */
110	adrp	x0, _start		/* x0 <- Runtime value of _start */
111	add	x0, x0, #:lo12:_start
112	ldr	x9, _TEXT_BASE		/* x9 <- Linked value of _start */
113	sub	x9, x9, x0		/* x9 <- Run-vs-link offset */
114	add	lr, lr, x9
115#endif
116	/* Add in link-vs-relocation offset */
117	ldr	x9, [x18, #GD_RELOC_OFF]	/* x9 <- gd->reloc_off */
118	add	lr, lr, x9	/* new return address after relocation */
119	ldr	x0, [x18, #GD_RELOCADDR]	/* x0 <- gd->relocaddr */
120	b	relocate_code
121
122relocation_return:
123
124/*
125 * Set up final (full) environment
126 */
127	bl	c_runtime_cpu_setup		/* still call old routine */
128#endif /* !CONFIG_SPL_BUILD */
129#if !defined(CONFIG_SPL_BUILD) || CONFIG_IS_ENABLED(FRAMEWORK)
130#if defined(CONFIG_SPL_BUILD)
131	bl	spl_relocate_stack_gd           /* may return NULL */
132	/* set up gd here, outside any C code, if new stack is returned */
133	cmp	x0, #0
134	csel	x18, x0, x18, ne
135	/*
136	 * Perform 'sp = (x0 != NULL) ? x0 : sp' while working
137	 * around the constraint that conditional moves can not
138	 * have 'sp' as an operand
139	 */
140	mov	x1, sp
141	cmp	x0, #0
142	csel	x0, x0, x1, ne
143	mov	sp, x0
144#endif
145
146/*
147 * Clear BSS section
148 */
149	ldr	x0, =__bss_start		/* this is auto-relocated! */
150	ldr	x1, =__bss_end			/* this is auto-relocated! */
151clear_loop:
152	str	xzr, [x0], #8
153	cmp	x0, x1
154	b.lo	clear_loop
155
156	/* call board_init_r(gd_t *id, ulong dest_addr) */
157	mov	x0, x18				/* gd_t */
158	ldr	x1, [x18, #GD_RELOCADDR]	/* dest_addr */
159	b	board_init_r			/* PC relative jump */
160
161	/* NOTREACHED - board_init_r() does not return */
162#endif
163
164ENDPROC(_main)
165