xref: /openbmc/u-boot/arch/mips/cpu/start.S (revision 038be18f) 
1/*
2 *  Startup Code for MIPS32 CPU-core
3 *
4 *  Copyright (c) 2003	Wolfgang Denk <wd@denx.de>
5 *
6 * SPDX-License-Identifier:	GPL-2.0+
7 */
8
9#include <asm-offsets.h>
10#include <config.h>
11#include <asm/asm.h>
12#include <asm/regdef.h>
13#include <asm/mipsregs.h>
14
15#ifndef CONFIG_SYS_MIPS_CACHE_MODE
16#define CONFIG_SYS_MIPS_CACHE_MODE CONF_CM_CACHABLE_NONCOHERENT
17#endif
18
19#ifndef CONFIG_SYS_INIT_SP_ADDR
20#define CONFIG_SYS_INIT_SP_ADDR	(CONFIG_SYS_SDRAM_BASE + \
21				CONFIG_SYS_INIT_SP_OFFSET)
22#endif
23
24#ifdef CONFIG_32BIT
25# define MIPS_RELOC	3
26# define STATUS_SET	0
27#endif
28
29#ifdef CONFIG_64BIT
30# ifdef CONFIG_SYS_LITTLE_ENDIAN
31#  define MIPS64_R_INFO(ssym, r_type3, r_type2, r_type) \
32	(((r_type) << 24) | ((r_type2) << 16) | ((r_type3) << 8) | (ssym))
33# else
34#  define MIPS64_R_INFO(ssym, r_type3, r_type2, r_type) \
35	((r_type) | ((r_type2) << 8) | ((r_type3) << 16) | (ssym) << 24)
36# endif
37# define MIPS_RELOC	MIPS64_R_INFO(0x00, 0x00, 0x12, 0x03)
38# define STATUS_SET	ST0_KX
39#endif
40
41	/*
42	 * For the moment disable interrupts, mark the kernel mode and
43	 * set ST0_KX so that the CPU does not spit fire when using
44	 * 64-bit addresses.
45	 */
46	.macro	setup_c0_status set clr
47	.set	push
48	mfc0	t0, CP0_STATUS
49	or	t0, ST0_CU0 | \set | 0x1f | \clr
50	xor	t0, 0x1f | \clr
51	mtc0	t0, CP0_STATUS
52	.set	noreorder
53	sll	zero, 3				# ehb
54	.set	pop
55	.endm
56
57	.set noreorder
58
59	.globl _start
60	.text
61_start:
62	/* U-boot entry point */
63	b	reset
64	 nop
65
66	.org 0x10
67#if defined(CONFIG_SYS_XWAY_EBU_BOOTCFG)
68	/*
69	 * Almost all Lantiq XWAY SoC devices have an external bus unit (EBU) to
70	 * access external NOR flashes. If the board boots from NOR flash the
71	 * internal BootROM does a blind read at address 0xB0000010 to read the
72	 * initial configuration for that EBU in order to access the flash
73	 * device with correct parameters. This config option is board-specific.
74	 */
75	.word CONFIG_SYS_XWAY_EBU_BOOTCFG
76	.word 0x0
77#elif defined(CONFIG_MALTA)
78	/*
79	 * Linux expects the Board ID here.
80	 */
81	.word 0x00000420	# 0x420 (Malta Board with CoreLV)
82	.word 0x00000000
83#endif
84
85	.org 0x200
86	/* TLB refill, 32 bit task */
871:	b	1b
88	 nop
89
90	.org 0x280
91	/* XTLB refill, 64 bit task */
921:	b	1b
93	 nop
94
95	.org 0x300
96	/* Cache error exception */
971:	b	1b
98	 nop
99
100	.org 0x380
101	/* General exception */
1021:	b	1b
103	 nop
104
105	.org 0x400
106	/* Catch interrupt exceptions */
1071:	b	1b
108	 nop
109
110	.org 0x480
111	/* EJTAG debug exception */
1121:	b	1b
113	 nop
114
115	.align 4
116reset:
117
118	/* Clear watch registers */
119	MTC0	zero, CP0_WATCHLO
120	MTC0	zero, CP0_WATCHHI
121
122	/* WP(Watch Pending), SW0/1 should be cleared */
123	mtc0	zero, CP0_CAUSE
124
125	setup_c0_status STATUS_SET 0
126
127	/* Init Timer */
128	mtc0	zero, CP0_COUNT
129	mtc0	zero, CP0_COMPARE
130
131#ifndef CONFIG_SKIP_LOWLEVEL_INIT
132	/* CONFIG0 register */
133	li	t0, CONF_CM_UNCACHED
134	mtc0	t0, CP0_CONFIG
135#endif
136
137	/*
138	 * Initialize $gp, force pointer sized alignment of bal instruction to
139	 * forbid the compiler to put nop's between bal and _gp. This is
140	 * required to keep _gp and ra aligned to 8 byte.
141	 */
142	.align	PTRLOG
143	bal	1f
144	 nop
145	PTR	_gp
1461:
147	PTR_L	gp, 0(ra)
148
149#ifndef CONFIG_SKIP_LOWLEVEL_INIT
150	/* Initialize any external memory */
151	PTR_LA	t9, lowlevel_init
152	jalr	t9
153	 nop
154
155	/* Initialize caches... */
156	PTR_LA	t9, mips_cache_reset
157	jalr	t9
158	 nop
159
160	/* ... and enable them */
161	li	t0, CONFIG_SYS_MIPS_CACHE_MODE
162	mtc0	t0, CP0_CONFIG
163#endif
164
165	/* Set up temporary stack */
166	PTR_LI	t0, -16
167	PTR_LI	t1, CONFIG_SYS_INIT_SP_ADDR
168	and	sp, t1, t0		# force 16 byte alignment
169	PTR_SUB	sp, sp, GD_SIZE		# reserve space for gd
170	and	sp, sp, t0		# force 16 byte alignment
171	move	k0, sp			# save gd pointer
172#ifdef CONFIG_SYS_MALLOC_F_LEN
173	PTR_LI	t2, CONFIG_SYS_MALLOC_F_LEN
174	PTR_SUB	sp, sp, t2		# reserve space for early malloc
175	and	sp, sp, t0		# force 16 byte alignment
176#endif
177	move	fp, sp
178
179	/* Clear gd */
180	move	t0, k0
1811:
182	sw	zero, 0(t0)
183	blt	t0, t1, 1b
184	 PTR_ADDI t0, 4
185
186#ifdef CONFIG_SYS_MALLOC_F_LEN
187	PTR_ADDU t0, k0, GD_MALLOC_BASE	# gd->malloc_base offset
188	sw	sp, 0(t0)
189#endif
190
191	PTR_LA	t9, board_init_f
192	jr	t9
193	 move	ra, zero
194
195/*
196 * void relocate_code (addr_sp, gd, addr_moni)
197 *
198 * This "function" does not return, instead it continues in RAM
199 * after relocating the monitor code.
200 *
201 * a0 = addr_sp
202 * a1 = gd
203 * a2 = destination address
204 */
205	.globl	relocate_code
206	.ent	relocate_code
207relocate_code:
208	move	sp, a0			# set new stack pointer
209	move	fp, sp
210
211	move	s0, a1			# save gd in s0
212	move	s2, a2			# save destination address in s2
213
214	PTR_LI	t0, CONFIG_SYS_MONITOR_BASE
215	PTR_SUB	s1, s2, t0		# s1 <-- relocation offset
216
217	PTR_LA	t3, in_ram
218	PTR_L	t2, -(3 * PTRSIZE)(t3)	# t2 <-- __image_copy_end
219	move	t1, a2
220
221	PTR_ADD	gp, s1			# adjust gp
222
223	/*
224	 * t0 = source address
225	 * t1 = target address
226	 * t2 = source end address
227	 */
2281:
229	lw	t3, 0(t0)
230	sw	t3, 0(t1)
231	PTR_ADDU t0, 4
232	blt	t0, t2, 1b
233	 PTR_ADDU t1, 4
234
235	/* If caches were enabled, we would have to flush them here. */
236	PTR_SUB	a1, t1, s2		# a1 <-- size
237	PTR_LA	t9, flush_cache
238	jalr	t9
239	 move	a0, s2			# a0 <-- destination address
240
241	/* Jump to where we've relocated ourselves */
242	PTR_ADDI t0, s2, in_ram - _start
243	jr	t0
244	 nop
245
246	PTR	__rel_dyn_end
247	PTR	__rel_dyn_start
248	PTR	__image_copy_end
249	PTR	_GLOBAL_OFFSET_TABLE_
250	PTR	num_got_entries
251
252in_ram:
253	/*
254	 * Now we want to update GOT.
255	 *
256	 * GOT[0] is reserved. GOT[1] is also reserved for the dynamic object
257	 * generated by GNU ld. Skip these reserved entries from relocation.
258	 */
259	PTR_L	t3, -(1 * PTRSIZE)(t0)	# t3 <-- num_got_entries
260	PTR_L	t8, -(2 * PTRSIZE)(t0)	# t8 <-- _GLOBAL_OFFSET_TABLE_
261	PTR_ADD	t8, s1			# t8 now holds relocated _G_O_T_
262	PTR_ADDI t8, t8, 2 * PTRSIZE	# skipping first two entries
263	PTR_LI	t2, 2
2641:
265	PTR_L	t1, 0(t8)
266	beqz	t1, 2f
267	 PTR_ADD t1, s1
268	PTR_S	t1, 0(t8)
2692:
270	PTR_ADDI t2, 1
271	blt	t2, t3, 1b
272	 PTR_ADDI t8, PTRSIZE
273
274	/* Update dynamic relocations */
275	PTR_L	t1, -(4 * PTRSIZE)(t0)	# t1 <-- __rel_dyn_start
276	PTR_L	t2, -(5 * PTRSIZE)(t0)	# t2 <-- __rel_dyn_end
277
278	b	2f			# skip first reserved entry
279	 PTR_ADDI t1, 2 * PTRSIZE
280
2811:
282	lw	t8, -4(t1)		# t8 <-- relocation info
283
284	PTR_LI	t3, MIPS_RELOC
285	bne	t8, t3, 2f		# skip non-MIPS_RELOC entries
286	 nop
287
288	PTR_L	t3, -(2 * PTRSIZE)(t1)	# t3 <-- location to fix up in FLASH
289
290	PTR_L	t8, 0(t3)		# t8 <-- original pointer
291	PTR_ADD	t8, s1			# t8 <-- adjusted pointer
292
293	PTR_ADD	t3, s1			# t3 <-- location to fix up in RAM
294	PTR_S	t8, 0(t3)
295
2962:
297	blt	t1, t2, 1b
298	 PTR_ADDI t1, 2 * PTRSIZE	# each rel.dyn entry is 2*PTRSIZE bytes
299
300	/*
301	 * Clear BSS
302	 *
303	 * GOT is now relocated. Thus __bss_start and __bss_end can be
304	 * accessed directly via $gp.
305	 */
306	PTR_LA	t1, __bss_start		# t1 <-- __bss_start
307	PTR_LA	t2, __bss_end		# t2 <-- __bss_end
308
3091:
310	PTR_S	zero, 0(t1)
311	blt	t1, t2, 1b
312	 PTR_ADDI t1, PTRSIZE
313
314	move	a0, s0			# a0 <-- gd
315	move	a1, s2
316	PTR_LA	t9, board_init_r
317	jr	t9
318	 move	ra, zero
319
320	.end	relocate_code
321