xref: /openbmc/linux/arch/arm/kernel/head-common.S (revision 4f3db074) 
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#include <asm/assembler.h>
14
15#define ATAG_CORE 0x54410001
16#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
17#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
18
19#ifdef CONFIG_CPU_BIG_ENDIAN
20#define OF_DT_MAGIC 0xd00dfeed
21#else
22#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
23#endif
24
25/*
26 * Exception handling.  Something went wrong and we can't proceed.  We
27 * ought to tell the user, but since we don't have any guarantee that
28 * we're even running on the right architecture, we do virtually nothing.
29 *
30 * If CONFIG_DEBUG_LL is set we try to print out something about the error
31 * and hope for the best (useful if bootloader fails to pass a proper
32 * machine ID for example).
33 */
34	__HEAD
35
36/* Determine validity of the r2 atags pointer.  The heuristic requires
37 * that the pointer be aligned, in the first 16k of physical RAM and
38 * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
39 * is selected, then it will also accept a dtb pointer.  Future revisions
40 * of this function may be more lenient with the physical address and
41 * may also be able to move the ATAGS block if necessary.
42 *
43 * Returns:
44 *  r2 either valid atags pointer, valid dtb pointer, or zero
45 *  r5, r6 corrupted
46 */
47__vet_atags:
48	tst	r2, #0x3			@ aligned?
49	bne	1f
50
51	ldr	r5, [r2, #0]
52#ifdef CONFIG_OF_FLATTREE
53	ldr	r6, =OF_DT_MAGIC		@ is it a DTB?
54	cmp	r5, r6
55	beq	2f
56#endif
57	cmp	r5, #ATAG_CORE_SIZE		@ is first tag ATAG_CORE?
58	cmpne	r5, #ATAG_CORE_SIZE_EMPTY
59	bne	1f
60	ldr	r5, [r2, #4]
61	ldr	r6, =ATAG_CORE
62	cmp	r5, r6
63	bne	1f
64
652:	ret	lr				@ atag/dtb pointer is ok
66
671:	mov	r2, #0
68	ret	lr
69ENDPROC(__vet_atags)
70
71/*
72 * The following fragment of code is executed with the MMU on in MMU mode,
73 * and uses absolute addresses; this is not position independent.
74 *
75 *  r0  = cp#15 control register
76 *  r1  = machine ID
77 *  r2  = atags/dtb pointer
78 *  r9  = processor ID
79 */
80	__INIT
81__mmap_switched:
82	adr	r3, __mmap_switched_data
83
84	ldmia	r3!, {r4, r5, r6, r7}
85	cmp	r4, r5				@ Copy data segment if needed
861:	cmpne	r5, r6
87	ldrne	fp, [r4], #4
88	strne	fp, [r5], #4
89	bne	1b
90
91	mov	fp, #0				@ Clear BSS (and zero fp)
921:	cmp	r6, r7
93	strcc	fp, [r6],#4
94	bcc	1b
95
96 ARM(	ldmia	r3, {r4, r5, r6, r7, sp})
97 THUMB(	ldmia	r3, {r4, r5, r6, r7}	)
98 THUMB(	ldr	sp, [r3, #16]		)
99	str	r9, [r4]			@ Save processor ID
100	str	r1, [r5]			@ Save machine type
101	str	r2, [r6]			@ Save atags pointer
102	cmp	r7, #0
103	strne	r0, [r7]			@ Save control register values
104	b	start_kernel
105ENDPROC(__mmap_switched)
106
107	.align	2
108	.type	__mmap_switched_data, %object
109__mmap_switched_data:
110	.long	__data_loc			@ r4
111	.long	_sdata				@ r5
112	.long	__bss_start			@ r6
113	.long	_end				@ r7
114	.long	processor_id			@ r4
115	.long	__machine_arch_type		@ r5
116	.long	__atags_pointer			@ r6
117#ifdef CONFIG_CPU_CP15
118	.long	cr_alignment			@ r7
119#else
120	.long	0				@ r7
121#endif
122	.long	init_thread_union + THREAD_START_SP @ sp
123	.size	__mmap_switched_data, . - __mmap_switched_data
124
125/*
126 * This provides a C-API version of __lookup_processor_type
127 */
128ENTRY(lookup_processor_type)
129	stmfd	sp!, {r4 - r6, r9, lr}
130	mov	r9, r0
131	bl	__lookup_processor_type
132	mov	r0, r5
133	ldmfd	sp!, {r4 - r6, r9, pc}
134ENDPROC(lookup_processor_type)
135
136	__FINIT
137	.text
138
139/*
140 * Read processor ID register (CP#15, CR0), and look up in the linker-built
141 * supported processor list.  Note that we can't use the absolute addresses
142 * for the __proc_info lists since we aren't running with the MMU on
143 * (and therefore, we are not in the correct address space).  We have to
144 * calculate the offset.
145 *
146 *	r9 = cpuid
147 * Returns:
148 *	r3, r4, r6 corrupted
149 *	r5 = proc_info pointer in physical address space
150 *	r9 = cpuid (preserved)
151 */
152__lookup_processor_type:
153	adr	r3, __lookup_processor_type_data
154	ldmia	r3, {r4 - r6}
155	sub	r3, r3, r4			@ get offset between virt&phys
156	add	r5, r5, r3			@ convert virt addresses to
157	add	r6, r6, r3			@ physical address space
1581:	ldmia	r5, {r3, r4}			@ value, mask
159	and	r4, r4, r9			@ mask wanted bits
160	teq	r3, r4
161	beq	2f
162	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
163	cmp	r5, r6
164	blo	1b
165	mov	r5, #0				@ unknown processor
1662:	ret	lr
167ENDPROC(__lookup_processor_type)
168
169/*
170 * Look in <asm/procinfo.h> for information about the __proc_info structure.
171 */
172	.align	2
173	.type	__lookup_processor_type_data, %object
174__lookup_processor_type_data:
175	.long	.
176	.long	__proc_info_begin
177	.long	__proc_info_end
178	.size	__lookup_processor_type_data, . - __lookup_processor_type_data
179
180__error_lpae:
181#ifdef CONFIG_DEBUG_LL
182	adr	r0, str_lpae
183	bl 	printascii
184	b	__error
185str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
186#else
187	b	__error
188#endif
189	.align
190ENDPROC(__error_lpae)
191
192__error_p:
193#ifdef CONFIG_DEBUG_LL
194	adr	r0, str_p1
195	bl	printascii
196	mov	r0, r9
197	bl	printhex8
198	adr	r0, str_p2
199	bl	printascii
200	b	__error
201str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant (0x"
202str_p2:	.asciz	").\n"
203	.align
204#endif
205ENDPROC(__error_p)
206
207__error:
208#ifdef CONFIG_ARCH_RPC
209/*
210 * Turn the screen red on a error - RiscPC only.
211 */
212	mov	r0, #0x02000000
213	mov	r3, #0x11
214	orr	r3, r3, r3, lsl #8
215	orr	r3, r3, r3, lsl #16
216	str	r3, [r0], #4
217	str	r3, [r0], #4
218	str	r3, [r0], #4
219	str	r3, [r0], #4
220#endif
2211:	mov	r0, r0
222	b	1b
223ENDPROC(__error)
224