xref: /openbmc/u-boot/arch/mips/cpu/start.S (revision baefb63a) 
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_INIT_SP_ADDR
16#define CONFIG_SYS_INIT_SP_ADDR	(CONFIG_SYS_SDRAM_BASE + \
17				CONFIG_SYS_INIT_SP_OFFSET)
18#endif
19
20#ifdef CONFIG_32BIT
21# define MIPS_RELOC	3
22# define STATUS_SET	0
23#endif
24
25#ifdef CONFIG_64BIT
26# ifdef CONFIG_SYS_LITTLE_ENDIAN
27#  define MIPS64_R_INFO(ssym, r_type3, r_type2, r_type) \
28	(((r_type) << 24) | ((r_type2) << 16) | ((r_type3) << 8) | (ssym))
29# else
30#  define MIPS64_R_INFO(ssym, r_type3, r_type2, r_type) \
31	((r_type) | ((r_type2) << 8) | ((r_type3) << 16) | (ssym) << 24)
32# endif
33# define MIPS_RELOC	MIPS64_R_INFO(0x00, 0x00, 0x12, 0x03)
34# define STATUS_SET	ST0_KX
35#endif
36
37	.set noreorder
38
39	.macro init_wr sel
40	MTC0	zero, CP0_WATCHLO,\sel
41	mtc0	t1, CP0_WATCHHI,\sel
42	mfc0	t0, CP0_WATCHHI,\sel
43	bgez	t0, wr_done
44	 nop
45	.endm
46
47	.macro uhi_mips_exception
48	move	k0, t9		# preserve t9 in k0
49	move	k1, a0		# preserve a0 in k1
50	li	t9, 15		# UHI exception operation
51	li	a0, 0		# Use hard register context
52	sdbbp	1		# Invoke UHI operation
53	.endm
54
55	.macro setup_stack_gd
56	li	t0, -16
57	PTR_LI	t1, CONFIG_SYS_INIT_SP_ADDR
58	and	sp, t1, t0		# force 16 byte alignment
59	PTR_SUBU \
60		sp, sp, GD_SIZE		# reserve space for gd
61	and	sp, sp, t0		# force 16 byte alignment
62	move	k0, sp			# save gd pointer
63#if CONFIG_VAL(SYS_MALLOC_F_LEN)
64	li	t2, CONFIG_VAL(SYS_MALLOC_F_LEN)
65	PTR_SUBU \
66		sp, sp, t2		# reserve space for early malloc
67	and	sp, sp, t0		# force 16 byte alignment
68#endif
69	move	fp, sp
70
71	/* Clear gd */
72	move	t0, k0
731:
74	PTR_S	zero, 0(t0)
75	blt	t0, t1, 1b
76	 PTR_ADDIU t0, PTRSIZE
77
78#if CONFIG_VAL(SYS_MALLOC_F_LEN)
79	PTR_S	sp, GD_MALLOC_BASE(k0)	# gd->malloc_base offset
80#endif
81	.endm
82
83ENTRY(_start)
84	/* U-Boot entry point */
85	b	reset
86	 mtc0	zero, CP0_COUNT	# clear cp0 count for most accurate boot timing
87
88#if defined(CONFIG_SYS_XWAY_EBU_BOOTCFG)
89	/*
90	 * Almost all Lantiq XWAY SoC devices have an external bus unit (EBU) to
91	 * access external NOR flashes. If the board boots from NOR flash the
92	 * internal BootROM does a blind read at address 0xB0000010 to read the
93	 * initial configuration for that EBU in order to access the flash
94	 * device with correct parameters. This config option is board-specific.
95	 */
96	.org 0x10
97	.word CONFIG_SYS_XWAY_EBU_BOOTCFG
98	.word 0x0
99#endif
100#if defined(CONFIG_MALTA)
101	/*
102	 * Linux expects the Board ID here.
103	 */
104	.org 0x10
105	.word 0x00000420	# 0x420 (Malta Board with CoreLV)
106	.word 0x00000000
107#endif
108
109#if defined(CONFIG_ROM_EXCEPTION_VECTORS)
110	/*
111	 * Exception vector entry points. When running from ROM, an exception
112	 * cannot be handled. Halt execution and transfer control to debugger,
113	 * if one is attached.
114	 */
115	.org 0x200
116	/* TLB refill, 32 bit task */
117	uhi_mips_exception
118
119	.org 0x280
120	/* XTLB refill, 64 bit task */
121	uhi_mips_exception
122
123	.org 0x300
124	/* Cache error exception */
125	uhi_mips_exception
126
127	.org 0x380
128	/* General exception */
129	uhi_mips_exception
130
131	.org 0x400
132	/* Catch interrupt exceptions */
133	uhi_mips_exception
134
135	.org 0x480
136	/* EJTAG debug exception */
1371:	b	1b
138	 nop
139
140	.org 0x500
141#endif
142
143reset:
144#if __mips_isa_rev >= 6
145	mfc0	t0, CP0_CONFIG, 5
146	and	t0, t0, MIPS_CONF5_VP
147	beqz	t0, 1f
148	 nop
149
150	b	2f
151	 mfc0	t0, CP0_GLOBALNUMBER
152#endif
153
154#ifdef CONFIG_ARCH_BMIPS
1551:	mfc0	t0, CP0_DIAGNOSTIC, 3
156	and	t0, t0, (1 << 31)
157#else
1581:	mfc0	t0, CP0_EBASE
159	and	t0, t0, EBASE_CPUNUM
160#endif
161
162	/* Hang if this isn't the first CPU in the system */
1632:	beqz	t0, 4f
164	 nop
1653:	wait
166	b	3b
167	 nop
168
169	/* Init CP0 Status */
1704:	mfc0	t0, CP0_STATUS
171	and	t0, ST0_IMPL
172	or	t0, ST0_BEV | ST0_ERL | STATUS_SET
173	mtc0	t0, CP0_STATUS
174
175	/*
176	 * Check whether CP0 Config1 is implemented. If not continue
177	 * with legacy Watch register initialization.
178	 */
179	mfc0	t0, CP0_CONFIG
180	bgez	t0, wr_legacy
181	 nop
182
183	/*
184	 * Check WR bit in CP0 Config1 to determine if Watch registers
185	 * are implemented.
186	 */
187	mfc0	t0, CP0_CONFIG, 1
188	andi	t0, (1 << 3)
189	beqz	t0, wr_done
190	 nop
191
192	/* Clear Watch Status bits and disable watch exceptions */
193	li	t1, 0x7		# Clear I, R and W conditions
194	init_wr	0
195	init_wr	1
196	init_wr	2
197	init_wr	3
198	init_wr	4
199	init_wr	5
200	init_wr	6
201	init_wr	7
202	b	wr_done
203	 nop
204
205wr_legacy:
206	MTC0	zero, CP0_WATCHLO
207	mtc0	zero, CP0_WATCHHI
208
209wr_done:
210	/* Clear WP, IV and SW interrupts */
211	mtc0	zero, CP0_CAUSE
212
213	/* Clear timer interrupt (CP0_COUNT cleared on branch to 'reset') */
214	mtc0	zero, CP0_COMPARE
215
216#ifndef CONFIG_SKIP_LOWLEVEL_INIT
217	mfc0	t0, CP0_CONFIG
218	and	t0, t0, MIPS_CONF_IMPL
219	or	t0, t0, CONF_CM_UNCACHED
220	mtc0	t0, CP0_CONFIG
221	ehb
222#endif
223
224#ifdef CONFIG_MIPS_CM
225	PTR_LA	t9, mips_cm_map
226	jalr	t9
227	 nop
228#endif
229
230#ifdef CONFIG_MIPS_INIT_STACK_IN_SRAM
231	/* Set up initial stack and global data */
232	setup_stack_gd
233
234# ifdef CONFIG_DEBUG_UART
235	/* Earliest point to set up debug uart */
236	PTR_LA	t9, debug_uart_init
237	jalr	t9
238	 nop
239# endif
240#endif
241
242#ifndef CONFIG_SKIP_LOWLEVEL_INIT
243# ifdef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
244	/* Initialize any external memory */
245	PTR_LA	t9, lowlevel_init
246	jalr	t9
247	 nop
248# endif
249
250	/* Initialize caches... */
251	PTR_LA	t9, mips_cache_reset
252	jalr	t9
253	 nop
254
255# ifndef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
256	/* Initialize any external memory */
257	PTR_LA	t9, lowlevel_init
258	jalr	t9
259	 nop
260# endif
261#endif
262
263#ifndef CONFIG_MIPS_INIT_STACK_IN_SRAM
264	/* Set up initial stack and global data */
265	setup_stack_gd
266
267# ifdef CONFIG_DEBUG_UART
268	/* Earliest point to set up debug uart */
269	PTR_LA	t9, debug_uart_init
270	jalr	t9
271	 nop
272# endif
273#endif
274
275	move	a0, zero		# a0 <-- boot_flags = 0
276	PTR_LA	t9, board_init_f
277
278	jr	t9
279	 move	ra, zero
280
281	END(_start)
282