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
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
|
/*
* File : start.S
* This file is part of RT-Thread RTOS
* COPYRIGHT (C) 2006, RT-Thread Development Team
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://openlab.rt-thread.com/license/LICENSE
*
* Change Logs:
* Date Author Notes
* 2006-08-31 Bernard first version
*/
/* Internal Memory Base Addresses */
.equ FLASH_BASE, 0x00100000
.equ RAM_BASE, 0x00200000
/* Stack Configuration */
.equ TOP_STACK, 0x00204000
.equ UND_STACK_SIZE, 0x00000100
.equ SVC_STACK_SIZE, 0x00000400
.equ ABT_STACK_SIZE, 0x00000100
.equ FIQ_STACK_SIZE, 0x00000100
.equ IRQ_STACK_SIZE, 0x00000100
.equ USR_STACK_SIZE, 0x00000004
/* ARM architecture definitions */
.equ MODE_USR, 0x10
.equ MODE_FIQ, 0x11
.equ MODE_IRQ, 0x12
.equ MODE_SVC, 0x13
.equ MODE_ABT, 0x17
.equ MODE_UND, 0x1B
.equ MODE_SYS, 0x1F
.equ I_BIT, 0x80 /* when this bit is set, IRQ is disabled */
.equ F_BIT, 0x40 /* when this bit is set, FIQ is disabled */
.section .init, "ax"
.code 32
.align 0
.globl _start
_start:
b reset
ldr pc, _vector_undef
ldr pc, _vector_swi
ldr pc, _vector_pabt
ldr pc, _vector_dabt
nop /* reserved vector */
ldr pc, _vector_irq
ldr pc, _vector_fiq
_vector_undef: .word vector_undef
_vector_swi: .word vector_swi
_vector_pabt: .word vector_pabt
_vector_dabt: .word vector_dabt
_vector_resv: .word vector_resv
_vector_irq: .word vector_irq
_vector_fiq: .word vector_fiq
/*
* rtthread bss start and end
* which are defined in linker script
*/
.globl _bss_start
_bss_start: .word __bss_start
.globl _bss_end
_bss_end: .word __bss_end
/* the system entry */
reset:
/* disable watchdog */
ldr r0, =0xFFFFFD40
ldr r1, =0x00008000
str r1, [r0, #0x04]
/* enable the main oscillator */
ldr r0, =0xFFFFFC00
ldr r1, =0x00000601
str r1, [r0, #0x20]
/* wait for main oscillator to stabilize */
moscs_loop:
ldr r2, [r0, #0x68]
ands r2, r2, #1
beq moscs_loop
/* set up the PLL */
ldr r1, =0x00191C05
str r1, [r0, #0x2C]
/* wait for PLL to lock */
pll_loop:
ldr r2, [r0, #0x68]
ands r2, r2, #0x04
beq pll_loop
/* select clock */
ldr r1, =0x00000007
str r1, [r0, #0x30]
#ifdef __FLASH_BUILD__
/* copy exception vectors into internal sram */
/*
mov r8, #RAM_BASE
ldr r9, =_start
ldmia r9!, {r0-r7}
stmia r8!, {r0-r7}
ldmia r9!, {r0-r6}
stmia r8!, {r0-r6}
*/
#endif
/* setup stack for each mode */
ldr r0, =TOP_STACK
/* set stack */
/* undefined instruction mode */
msr cpsr_c, #MODE_UND|I_BIT|F_BIT
mov sp, r0
sub r0, r0, #UND_STACK_SIZE
/* abort mode */
msr cpsr_c, #MODE_ABT|I_BIT|F_BIT
mov sp, r0
sub r0, r0, #ABT_STACK_SIZE
/* FIQ mode */
msr cpsr_c, #MODE_FIQ|I_BIT|F_BIT
mov sp, r0
sub r0, r0, #FIQ_STACK_SIZE
/* IRQ mode */
msr cpsr_c, #MODE_IRQ|I_BIT|F_BIT
mov sp, r0
sub r0, r0, #IRQ_STACK_SIZE
/* supervisor mode */
msr cpsr_c, #MODE_SVC|I_BIT|F_BIT
mov sp, r0
/* remap SRAM to 0x0000 */
/*
ldr r0, =0xFFFFFF00
mov r1, #0x01
str r1, [r0]
*/
/* mask all IRQs */
ldr r1, =0xFFFFF124
ldr r0, =0XFFFFFFFF
str r0, [r1]
/* copy .data to SRAM */
ldr r1, =_sidata /* .data start in image */
ldr r2, =_edata /* .data end in image */
ldr r3, =_sdata /* sram data start */
data_loop:
ldr r0, [r1, #0]
str r0, [r3]
add r1, r1, #4
add r3, r3, #4
cmp r3, r2 /* check if data to clear */
blo data_loop /* loop until done */
/* clear .bss */
mov r0,#0 /* get a zero */
ldr r1,=__bss_start /* bss start */
ldr r2,=__bss_end /* bss end */
bss_loop:
cmp r1,r2 /* check if data to clear */
strlo r0,[r1],#4 /* clear 4 bytes */
blo bss_loop /* loop until done */
/* call C++ constructors of global objects */
ldr r0, =__ctors_start__
ldr r1, =__ctors_end__
ctor_loop:
cmp r0, r1
beq ctor_end
ldr r2, [r0], #4
stmfd sp!, {r0-r1}
mov lr, pc
bx r2
ldmfd sp!, {r0-r1}
b ctor_loop
ctor_end:
/* start RT-Thread Kernel */
ldr pc, _rtthread_startup
_rtthread_startup: .word rtthread_startup
/* exception handlers */
vector_undef: b vector_undef
vector_swi : b vector_swi
vector_pabt : b vector_pabt
vector_dabt : b vector_dabt
vector_resv : b vector_resv
.globl rt_interrupt_enter
.globl rt_interrupt_leave
.globl rt_thread_switch_interrupt_flag
.globl rt_interrupt_from_thread
.globl rt_interrupt_to_thread
vector_irq:
stmfd sp!, {r0-r12,lr}
bl rt_interrupt_enter
bl rt_hw_trap_irq
bl rt_interrupt_leave
/*
* if rt_thread_switch_interrupt_flag set, jump to
* rt_hw_context_switch_interrupt_do and don't return
*/
ldr r0, =rt_thread_switch_interrupt_flag
ldr r1, [r0]
cmp r1, #1
beq rt_hw_context_switch_interrupt_do
ldmfd sp!, {r0-r12,lr}
subs pc, lr, #4
vector_fiq:
stmfd sp!,{r0-r7,lr}
bl rt_hw_trap_fiq
ldmfd sp!,{r0-r7,lr}
subs pc,lr,#4
/*
* void rt_hw_context_switch_interrupt_do(rt_base_t flag)
*/
rt_hw_context_switch_interrupt_do:
mov r1, #0 @ clear flag
str r1, [r0]
ldmfd sp!, {r0-r12,lr}@ reload saved registers
stmfd sp!, {r0-r3} @ save r0-r3
mov r1, sp
add sp, sp, #16 @ restore sp
sub r2, lr, #4 @ save old task's pc to r2
mrs r3, spsr @ disable interrupt
orr r0, r3, #I_BIT|F_BIT
msr spsr_c, r0
ldr r0, =.+8 @ switch to interrupted task's stack
movs pc, r0
stmfd sp!, {r2} @ push old task's pc
stmfd sp!, {r4-r12,lr}@ push old task's lr,r12-r4
mov r4, r1 @ Special optimised code below
mov r5, r3
ldmfd r4!, {r0-r3}
stmfd sp!, {r0-r3} @ push old task's r3-r0
stmfd sp!, {r5} @ push old task's psr
mrs r4, spsr
stmfd sp!, {r4} @ push old task's spsr
ldr r4, =rt_interrupt_from_thread
ldr r5, [r4]
str sp, [r5] @ store sp in preempted tasks's TCB
ldr r6, =rt_interrupt_to_thread
ldr r6, [r6]
ldr sp, [r6] @ get new task's stack pointer
ldmfd sp!, {r4} @ pop new task's spsr
msr SPSR_cxsf, r4
ldmfd sp!, {r4} @ pop new task's psr
msr CPSR_cxsf, r4
ldmfd sp!, {r0-r12,lr,pc} @ pop new task's r0-r12,lr & pc
|
