xref: /openbmc/linux/arch/arm/kernel/head-common.S (revision b6dcefde) 
1/*
2 *  linux/arch/arm/kernel/head-common.S
3 *
4 *  Copyright (C) 1994-2002 Russell King
5 *  Copyright (c) 2003 ARM Limited
6 *  All Rights Reserved
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
11 *
12 */
13
14#define ATAG_CORE 0x54410001
15#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
16#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
17
18	.align	2
19	.type	__switch_data, %object
20__switch_data:
21	.long	__mmap_switched
22	.long	__data_loc			@ r4
23	.long	_data				@ r5
24	.long	__bss_start			@ r6
25	.long	_end				@ r7
26	.long	processor_id			@ r4
27	.long	__machine_arch_type		@ r5
28	.long	__atags_pointer			@ r6
29	.long	cr_alignment			@ r7
30	.long	init_thread_union + THREAD_START_SP @ sp
31
32/*
33 * The following fragment of code is executed with the MMU on in MMU mode,
34 * and uses absolute addresses; this is not position independent.
35 *
36 *  r0  = cp#15 control register
37 *  r1  = machine ID
38 *  r2  = atags pointer
39 *  r9  = processor ID
40 */
41__mmap_switched:
42	adr	r3, __switch_data + 4
43
44	ldmia	r3!, {r4, r5, r6, r7}
45	cmp	r4, r5				@ Copy data segment if needed
461:	cmpne	r5, r6
47	ldrne	fp, [r4], #4
48	strne	fp, [r5], #4
49	bne	1b
50
51	mov	fp, #0				@ Clear BSS (and zero fp)
521:	cmp	r6, r7
53	strcc	fp, [r6],#4
54	bcc	1b
55
56 ARM(	ldmia	r3, {r4, r5, r6, r7, sp})
57 THUMB(	ldmia	r3, {r4, r5, r6, r7}	)
58 THUMB(	ldr	sp, [r3, #16]		)
59	str	r9, [r4]			@ Save processor ID
60	str	r1, [r5]			@ Save machine type
61	str	r2, [r6]			@ Save atags pointer
62	bic	r4, r0, #CR_A			@ Clear 'A' bit
63	stmia	r7, {r0, r4}			@ Save control register values
64	b	start_kernel
65ENDPROC(__mmap_switched)
66
67/*
68 * Exception handling.  Something went wrong and we can't proceed.  We
69 * ought to tell the user, but since we don't have any guarantee that
70 * we're even running on the right architecture, we do virtually nothing.
71 *
72 * If CONFIG_DEBUG_LL is set we try to print out something about the error
73 * and hope for the best (useful if bootloader fails to pass a proper
74 * machine ID for example).
75 */
76__error_p:
77#ifdef CONFIG_DEBUG_LL
78	adr	r0, str_p1
79	bl	printascii
80	mov	r0, r9
81	bl	printhex8
82	adr	r0, str_p2
83	bl	printascii
84	b	__error
85str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant (0x"
86str_p2:	.asciz	").\n"
87	.align
88#endif
89ENDPROC(__error_p)
90
91__error_a:
92#ifdef CONFIG_DEBUG_LL
93	mov	r4, r1				@ preserve machine ID
94	adr	r0, str_a1
95	bl	printascii
96	mov	r0, r4
97	bl	printhex8
98	adr	r0, str_a2
99	bl	printascii
100	adr	r3, 4f
101	ldmia	r3, {r4, r5, r6}		@ get machine desc list
102	sub	r4, r3, r4			@ get offset between virt&phys
103	add	r5, r5, r4			@ convert virt addresses to
104	add	r6, r6, r4			@ physical address space
1051:	ldr	r0, [r5, #MACHINFO_TYPE]	@ get machine type
106	bl	printhex8
107	mov	r0, #'\t'
108	bl	printch
109	ldr     r0, [r5, #MACHINFO_NAME]	@ get machine name
110	add	r0, r0, r4
111	bl	printascii
112	mov	r0, #'\n'
113	bl	printch
114	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
115	cmp	r5, r6
116	blo	1b
117	adr	r0, str_a3
118	bl	printascii
119	b	__error
120ENDPROC(__error_a)
121
122str_a1:	.asciz	"\nError: unrecognized/unsupported machine ID (r1 = 0x"
123str_a2:	.asciz	").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
124str_a3:	.asciz	"\nPlease check your kernel config and/or bootloader.\n"
125	.align
126#endif
127
128__error:
129#ifdef CONFIG_ARCH_RPC
130/*
131 * Turn the screen red on a error - RiscPC only.
132 */
133	mov	r0, #0x02000000
134	mov	r3, #0x11
135	orr	r3, r3, r3, lsl #8
136	orr	r3, r3, r3, lsl #16
137	str	r3, [r0], #4
138	str	r3, [r0], #4
139	str	r3, [r0], #4
140	str	r3, [r0], #4
141#endif
1421:	mov	r0, r0
143	b	1b
144ENDPROC(__error)
145
146
147/*
148 * Read processor ID register (CP#15, CR0), and look up in the linker-built
149 * supported processor list.  Note that we can't use the absolute addresses
150 * for the __proc_info lists since we aren't running with the MMU on
151 * (and therefore, we are not in the correct address space).  We have to
152 * calculate the offset.
153 *
154 *	r9 = cpuid
155 * Returns:
156 *	r3, r4, r6 corrupted
157 *	r5 = proc_info pointer in physical address space
158 *	r9 = cpuid (preserved)
159 */
160__lookup_processor_type:
161	adr	r3, 3f
162	ldmia	r3, {r5 - r7}
163	add	r3, r3, #8
164	sub	r3, r3, r7			@ get offset between virt&phys
165	add	r5, r5, r3			@ convert virt addresses to
166	add	r6, r6, r3			@ physical address space
1671:	ldmia	r5, {r3, r4}			@ value, mask
168	and	r4, r4, r9			@ mask wanted bits
169	teq	r3, r4
170	beq	2f
171	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
172	cmp	r5, r6
173	blo	1b
174	mov	r5, #0				@ unknown processor
1752:	mov	pc, lr
176ENDPROC(__lookup_processor_type)
177
178/*
179 * This provides a C-API version of the above function.
180 */
181ENTRY(lookup_processor_type)
182	stmfd	sp!, {r4 - r7, r9, lr}
183	mov	r9, r0
184	bl	__lookup_processor_type
185	mov	r0, r5
186	ldmfd	sp!, {r4 - r7, r9, pc}
187ENDPROC(lookup_processor_type)
188
189/*
190 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for
191 * more information about the __proc_info and __arch_info structures.
192 */
193	.align	2
1943:	.long	__proc_info_begin
195	.long	__proc_info_end
1964:	.long	.
197	.long	__arch_info_begin
198	.long	__arch_info_end
199
200/*
201 * Lookup machine architecture in the linker-build list of architectures.
202 * Note that we can't use the absolute addresses for the __arch_info
203 * lists since we aren't running with the MMU on (and therefore, we are
204 * not in the correct address space).  We have to calculate the offset.
205 *
206 *  r1 = machine architecture number
207 * Returns:
208 *  r3, r4, r6 corrupted
209 *  r5 = mach_info pointer in physical address space
210 */
211__lookup_machine_type:
212	adr	r3, 4b
213	ldmia	r3, {r4, r5, r6}
214	sub	r3, r3, r4			@ get offset between virt&phys
215	add	r5, r5, r3			@ convert virt addresses to
216	add	r6, r6, r3			@ physical address space
2171:	ldr	r3, [r5, #MACHINFO_TYPE]	@ get machine type
218	teq	r3, r1				@ matches loader number?
219	beq	2f				@ found
220	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
221	cmp	r5, r6
222	blo	1b
223	mov	r5, #0				@ unknown machine
2242:	mov	pc, lr
225ENDPROC(__lookup_machine_type)
226
227/*
228 * This provides a C-API version of the above function.
229 */
230ENTRY(lookup_machine_type)
231	stmfd	sp!, {r4 - r6, lr}
232	mov	r1, r0
233	bl	__lookup_machine_type
234	mov	r0, r5
235	ldmfd	sp!, {r4 - r6, pc}
236ENDPROC(lookup_machine_type)
237
238/* Determine validity of the r2 atags pointer.  The heuristic requires
239 * that the pointer be aligned, in the first 16k of physical RAM and
240 * that the ATAG_CORE marker is first and present.  Future revisions
241 * of this function may be more lenient with the physical address and
242 * may also be able to move the ATAGS block if necessary.
243 *
244 * r8  = machinfo
245 *
246 * Returns:
247 *  r2 either valid atags pointer, or zero
248 *  r5, r6 corrupted
249 */
250__vet_atags:
251	tst	r2, #0x3			@ aligned?
252	bne	1f
253
254	ldr	r5, [r2, #0]			@ is first tag ATAG_CORE?
255	cmp	r5, #ATAG_CORE_SIZE
256	cmpne	r5, #ATAG_CORE_SIZE_EMPTY
257	bne	1f
258	ldr	r5, [r2, #4]
259	ldr	r6, =ATAG_CORE
260	cmp	r5, r6
261	bne	1f
262
263	mov	pc, lr				@ atag pointer is ok
264
2651:	mov	r2, #0
266	mov	pc, lr
267ENDPROC(__vet_atags)
268