xref: /openbmc/u-boot/arch/mips/cpu/start.S (revision 2d1951fe) 
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#ifdef CONFIG_SYS_MALLOC_F_LEN
64	li	t2, CONFIG_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#ifdef CONFIG_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	/*
225	 * Initialize $gp, force pointer sized alignment of bal instruction to
226	 * forbid the compiler to put nop's between bal and _gp. This is
227	 * required to keep _gp and ra aligned to 8 byte.
228	 */
229	.align	PTRLOG
230	bal	1f
231	 nop
232	PTR	_gp
2331:
234	PTR_L	gp, 0(ra)
235
236#ifdef CONFIG_MIPS_CM
237	PTR_LA	t9, mips_cm_map
238	jalr	t9
239	 nop
240#endif
241
242#ifdef CONFIG_MIPS_INIT_STACK_IN_SRAM
243	/* Set up initial stack and global data */
244	setup_stack_gd
245
246# ifdef CONFIG_DEBUG_UART
247	/* Earliest point to set up debug uart */
248	PTR_LA	t9, debug_uart_init
249	jalr	t9
250	 nop
251# endif
252#endif
253
254#ifndef CONFIG_SKIP_LOWLEVEL_INIT
255# ifdef 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
262	/* Initialize caches... */
263	PTR_LA	t9, mips_cache_reset
264	jalr	t9
265	 nop
266
267# ifndef CONFIG_SYS_MIPS_CACHE_INIT_RAM_LOAD
268	/* Initialize any external memory */
269	PTR_LA	t9, lowlevel_init
270	jalr	t9
271	 nop
272# endif
273#endif
274
275#ifndef CONFIG_MIPS_INIT_STACK_IN_SRAM
276	/* Set up initial stack and global data */
277	setup_stack_gd
278
279# ifdef CONFIG_DEBUG_UART
280	/* Earliest point to set up debug uart */
281	PTR_LA	t9, debug_uart_init
282	jalr	t9
283	 nop
284# endif
285#endif
286
287	move	a0, zero		# a0 <-- boot_flags = 0
288	PTR_LA	t9, board_init_f
289
290	jr	t9
291	 move	ra, zero
292
293	END(_start)
294
295/*
296 * void relocate_code (addr_sp, gd, addr_moni)
297 *
298 * This "function" does not return, instead it continues in RAM
299 * after relocating the monitor code.
300 *
301 * a0 = addr_sp
302 * a1 = gd
303 * a2 = destination address
304 */
305ENTRY(relocate_code)
306	move	sp, a0			# set new stack pointer
307	move	fp, sp
308
309	move	s0, a1			# save gd in s0
310	move	s2, a2			# save destination address in s2
311
312	PTR_LI	t0, CONFIG_SYS_MONITOR_BASE
313	PTR_SUB	s1, s2, t0		# s1 <-- relocation offset
314
315	PTR_LA	t2, __image_copy_end
316	move	t1, a2
317
318	/*
319	 * t0 = source address
320	 * t1 = target address
321	 * t2 = source end address
322	 */
3231:
324	PTR_L	t3, 0(t0)
325	PTR_S	t3, 0(t1)
326	PTR_ADDU t0, PTRSIZE
327	blt	t0, t2, 1b
328	 PTR_ADDU t1, PTRSIZE
329
330	/*
331	 * Now we want to update GOT.
332	 *
333	 * GOT[0] is reserved. GOT[1] is also reserved for the dynamic object
334	 * generated by GNU ld. Skip these reserved entries from relocation.
335	 */
336	PTR_LA	t3, num_got_entries
337	PTR_LA	t8, _GLOBAL_OFFSET_TABLE_
338	PTR_ADD	t8, s1			# t8 now holds relocated _G_O_T_
339	PTR_ADDIU t8, t8, 2 * PTRSIZE	# skipping first two entries
340	PTR_LI	t2, 2
3411:
342	PTR_L	t1, 0(t8)
343	beqz	t1, 2f
344	 PTR_ADD t1, s1
345	PTR_S	t1, 0(t8)
3462:
347	PTR_ADDIU t2, 1
348	blt	t2, t3, 1b
349	 PTR_ADDIU t8, PTRSIZE
350
351	/* Update dynamic relocations */
352	PTR_LA	t1, __rel_dyn_start
353	PTR_LA	t2, __rel_dyn_end
354
355	b	2f			# skip first reserved entry
356	 PTR_ADDIU t1, 2 * PTRSIZE
357
3581:
359	lw	t8, -4(t1)		# t8 <-- relocation info
360
361	PTR_LI	t3, MIPS_RELOC
362	bne	t8, t3, 2f		# skip non-MIPS_RELOC entries
363	 nop
364
365	PTR_L	t3, -(2 * PTRSIZE)(t1)	# t3 <-- location to fix up in FLASH
366
367	PTR_L	t8, 0(t3)		# t8 <-- original pointer
368	PTR_ADD	t8, s1			# t8 <-- adjusted pointer
369
370	PTR_ADD	t3, s1			# t3 <-- location to fix up in RAM
371	PTR_S	t8, 0(t3)
372
3732:
374	blt	t1, t2, 1b
375	 PTR_ADDIU t1, 2 * PTRSIZE	# each rel.dyn entry is 2*PTRSIZE bytes
376
377	/*
378	 * Flush caches to ensure our newly modified instructions are visible
379	 * to the instruction cache. We're still running with the old GOT, so
380	 * apply the reloc offset to the start address.
381	 */
382	PTR_LA	a0, __text_start
383	PTR_LA	a1, __text_end
384	PTR_SUB	a1, a1, a0
385	PTR_LA	t9, flush_cache
386	jalr	t9
387	 PTR_ADD	a0, s1
388
389	PTR_ADD	gp, s1			# adjust gp
390
391	/*
392	 * Clear BSS
393	 *
394	 * GOT is now relocated. Thus __bss_start and __bss_end can be
395	 * accessed directly via $gp.
396	 */
397	PTR_LA	t1, __bss_start		# t1 <-- __bss_start
398	PTR_LA	t2, __bss_end		# t2 <-- __bss_end
399
4001:
401	PTR_S	zero, 0(t1)
402	blt	t1, t2, 1b
403	 PTR_ADDIU t1, PTRSIZE
404
405	move	a0, s0			# a0 <-- gd
406	move	a1, s2
407	PTR_LA	t9, board_init_r
408	jr	t9
409	 move	ra, zero
410
411	END(relocate_code)
412