1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
|
/*
* arch/xtensa/kernel/head.S
*
* Xtensa Processor startup code.
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2001 - 2008 Tensilica Inc.
*
* Chris Zankel <chris@zankel.net>
* Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
* Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
* Kevin Chea
*/
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/cacheasm.h>
#include <asm/initialize_mmu.h>
#include <linux/init.h>
#include <linux/linkage.h>
/*
* This module contains the entry code for kernel images. It performs the
* minimal setup needed to call the generic C routines.
*
* Prerequisites:
*
* - The kernel image has been loaded to the actual address where it was
* compiled to.
* - a2 contains either 0 or a pointer to a list of boot parameters.
* (see setup.c for more details)
*
*/
/*
* _start
*
* The bootloader passes a pointer to a list of boot parameters in a2.
*/
/* The first bytes of the kernel image must be an instruction, so we
* manually allocate and define the literal constant we need for a jx
* instruction.
*/
__HEAD
ENTRY(_start)
_j 2f
.align 4
1: .word _startup
2: l32r a0, 1b
jx a0
ENDPROC(_start)
.section .init.text, "ax"
ENTRY(_startup)
/* Disable interrupts and exceptions. */
movi a0, LOCKLEVEL
wsr a0, ps
/* Preserve the pointer to the boot parameter list in EXCSAVE_1 */
wsr a2, excsave1
/* Start with a fresh windowbase and windowstart. */
movi a1, 1
movi a0, 0
wsr a1, windowstart
wsr a0, windowbase
rsync
/* Set a0 to 0 for the remaining initialization. */
movi a0, 0
/* Clear debugging registers. */
#if XCHAL_HAVE_DEBUG
wsr a0, ibreakenable
wsr a0, icount
movi a1, 15
wsr a0, icountlevel
.set _index, 0
.rept XCHAL_NUM_DBREAK - 1
wsr a0, SREG_DBREAKC + _index
.set _index, _index + 1
.endr
#endif
/* Clear CCOUNT (not really necessary, but nice) */
wsr a0, ccount # not really necessary, but nice
/* Disable zero-loops. */
#if XCHAL_HAVE_LOOPS
wsr a0, lcount
#endif
/* Disable all timers. */
.set _index, 0
.rept XCHAL_NUM_TIMERS
wsr a0, SREG_CCOMPARE + _index
.set _index, _index + 1
.endr
/* Interrupt initialization. */
movi a2, XCHAL_INTTYPE_MASK_SOFTWARE | XCHAL_INTTYPE_MASK_EXTERN_EDGE
wsr a0, intenable
wsr a2, intclear
/* Disable coprocessors. */
#if XCHAL_HAVE_CP
wsr a0, cpenable
#endif
/* Set PS.INTLEVEL=LOCKLEVEL, PS.WOE=0, kernel stack, PS.EXCM=0
*
* Note: PS.EXCM must be cleared before using any loop
* instructions; otherwise, they are silently disabled, and
* at most one iteration of the loop is executed.
*/
movi a1, LOCKLEVEL
wsr a1, ps
rsync
/* Initialize the caches.
* a2, a3 are just working registers (clobbered).
*/
#if XCHAL_DCACHE_LINE_LOCKABLE
___unlock_dcache_all a2 a3
#endif
#if XCHAL_ICACHE_LINE_LOCKABLE
___unlock_icache_all a2 a3
#endif
___invalidate_dcache_all a2 a3
___invalidate_icache_all a2 a3
isync
initialize_mmu
/* Unpack data sections
*
* The linker script used to build the Linux kernel image
* creates a table located at __boot_reloc_table_start
* that contans the information what data needs to be unpacked.
*
* Uses a2-a7.
*/
movi a2, __boot_reloc_table_start
movi a3, __boot_reloc_table_end
1: beq a2, a3, 3f # no more entries?
l32i a4, a2, 0 # start destination (in RAM)
l32i a5, a2, 4 # end desination (in RAM)
l32i a6, a2, 8 # start source (in ROM)
addi a2, a2, 12 # next entry
beq a4, a5, 1b # skip, empty entry
beq a4, a6, 1b # skip, source and dest. are the same
2: l32i a7, a6, 0 # load word
addi a6, a6, 4
s32i a7, a4, 0 # store word
addi a4, a4, 4
bltu a4, a5, 2b
j 1b
3:
/* All code and initialized data segments have been copied.
* Now clear the BSS segment.
*/
movi a2, __bss_start # start of BSS
movi a3, __bss_stop # end of BSS
__loopt a2, a3, a4, 2
s32i a0, a2, 0
__endla a2, a4, 4
#if XCHAL_DCACHE_IS_WRITEBACK
/* After unpacking, flush the writeback cache to memory so the
* instructions/data are available.
*/
___flush_dcache_all a2 a3
#endif
/* Setup stack and enable window exceptions (keep irqs disabled) */
movi a1, init_thread_union
addi a1, a1, KERNEL_STACK_SIZE
movi a2, (1 << PS_WOE_BIT) | LOCKLEVEL
# WOE=1, INTLEVEL=LOCKLEVEL, UM=0
wsr a2, ps # (enable reg-windows; progmode stack)
rsync
/* Set up EXCSAVE[DEBUGLEVEL] to point to the Debug Exception Handler.*/
movi a2, debug_exception
wsr a2, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
/* Set up EXCSAVE[1] to point to the exc_table. */
movi a6, exc_table
xsr a6, excsave1
/* init_arch kick-starts the linux kernel */
movi a4, init_arch
callx4 a4
movi a4, start_kernel
callx4 a4
should_never_return:
j should_never_return
ENDPROC(_startup)
/*
* BSS section
*/
__PAGE_ALIGNED_BSS
#ifdef CONFIG_MMU
ENTRY(swapper_pg_dir)
.fill PAGE_SIZE, 1, 0
END(swapper_pg_dir)
#endif
ENTRY(empty_zero_page)
.fill PAGE_SIZE, 1, 0
END(empty_zero_page)
|
