xref: /openbmc/linux/arch/arm/kernel/head-common.S (revision 160b8e75) 
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
83	mov	r7, r1
84	mov	r8, r2
85	mov	r10, r0
86
87	adr	r4, __mmap_switched_data
88	mov	fp, #0
89
90#if defined(CONFIG_XIP_DEFLATED_DATA)
91   ARM(	ldr	sp, [r4], #4 )
92 THUMB(	ldr	sp, [r4] )
93 THUMB(	add	r4, #4 )
94	bl	__inflate_kernel_data		@ decompress .data to RAM
95	teq	r0, #0
96	bne	__error
97#elif defined(CONFIG_XIP_KERNEL)
98   ARM(	ldmia	r4!, {r0, r1, r2, sp} )
99 THUMB(	ldmia	r4!, {r0, r1, r2, r3} )
100 THUMB(	mov	sp, r3 )
101	sub	r2, r2, r1
102	bl	memcpy				@ copy .data to RAM
103#endif
104
105   ARM(	ldmia	r4!, {r0, r1, sp} )
106 THUMB(	ldmia	r4!, {r0, r1, r3} )
107 THUMB(	mov	sp, r3 )
108	sub	r2, r1, r0
109	mov	r1, #0
110	bl	memset				@ clear .bss
111
112	ldmia	r4, {r0, r1, r2, r3}
113	str	r9, [r0]			@ Save processor ID
114	str	r7, [r1]			@ Save machine type
115	str	r8, [r2]			@ Save atags pointer
116	cmp	r3, #0
117	strne	r10, [r3]			@ Save control register values
118	mov	lr, #0
119	b	start_kernel
120ENDPROC(__mmap_switched)
121
122	.align	2
123	.type	__mmap_switched_data, %object
124__mmap_switched_data:
125#ifdef CONFIG_XIP_KERNEL
126#ifndef CONFIG_XIP_DEFLATED_DATA
127	.long	_sdata				@ r0
128	.long	__data_loc			@ r1
129	.long	_edata_loc			@ r2
130#endif
131	.long	__bss_stop			@ sp (temporary stack in .bss)
132#endif
133
134	.long	__bss_start			@ r0
135	.long	__bss_stop			@ r1
136	.long	init_thread_union + THREAD_START_SP @ sp
137
138	.long	processor_id			@ r0
139	.long	__machine_arch_type		@ r1
140	.long	__atags_pointer			@ r2
141#ifdef CONFIG_CPU_CP15
142	.long	cr_alignment			@ r3
143#else
144	.long	0				@ r3
145#endif
146	.size	__mmap_switched_data, . - __mmap_switched_data
147
148/*
149 * This provides a C-API version of __lookup_processor_type
150 */
151ENTRY(lookup_processor_type)
152	stmfd	sp!, {r4 - r6, r9, lr}
153	mov	r9, r0
154	bl	__lookup_processor_type
155	mov	r0, r5
156	ldmfd	sp!, {r4 - r6, r9, pc}
157ENDPROC(lookup_processor_type)
158
159	__FINIT
160	.text
161
162/*
163 * Read processor ID register (CP#15, CR0), and look up in the linker-built
164 * supported processor list.  Note that we can't use the absolute addresses
165 * for the __proc_info lists since we aren't running with the MMU on
166 * (and therefore, we are not in the correct address space).  We have to
167 * calculate the offset.
168 *
169 *	r9 = cpuid
170 * Returns:
171 *	r3, r4, r6 corrupted
172 *	r5 = proc_info pointer in physical address space
173 *	r9 = cpuid (preserved)
174 */
175__lookup_processor_type:
176	adr	r3, __lookup_processor_type_data
177	ldmia	r3, {r4 - r6}
178	sub	r3, r3, r4			@ get offset between virt&phys
179	add	r5, r5, r3			@ convert virt addresses to
180	add	r6, r6, r3			@ physical address space
1811:	ldmia	r5, {r3, r4}			@ value, mask
182	and	r4, r4, r9			@ mask wanted bits
183	teq	r3, r4
184	beq	2f
185	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
186	cmp	r5, r6
187	blo	1b
188	mov	r5, #0				@ unknown processor
1892:	ret	lr
190ENDPROC(__lookup_processor_type)
191
192/*
193 * Look in <asm/procinfo.h> for information about the __proc_info structure.
194 */
195	.align	2
196	.type	__lookup_processor_type_data, %object
197__lookup_processor_type_data:
198	.long	.
199	.long	__proc_info_begin
200	.long	__proc_info_end
201	.size	__lookup_processor_type_data, . - __lookup_processor_type_data
202
203__error_lpae:
204#ifdef CONFIG_DEBUG_LL
205	adr	r0, str_lpae
206	bl 	printascii
207	b	__error
208str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
209#else
210	b	__error
211#endif
212	.align
213ENDPROC(__error_lpae)
214
215__error_p:
216#ifdef CONFIG_DEBUG_LL
217	adr	r0, str_p1
218	bl	printascii
219	mov	r0, r9
220	bl	printhex8
221	adr	r0, str_p2
222	bl	printascii
223	b	__error
224str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant (0x"
225str_p2:	.asciz	").\n"
226	.align
227#endif
228ENDPROC(__error_p)
229
230__error:
231#ifdef CONFIG_ARCH_RPC
232/*
233 * Turn the screen red on a error - RiscPC only.
234 */
235	mov	r0, #0x02000000
236	mov	r3, #0x11
237	orr	r3, r3, r3, lsl #8
238	orr	r3, r3, r3, lsl #16
239	str	r3, [r0], #4
240	str	r3, [r0], #4
241	str	r3, [r0], #4
242	str	r3, [r0], #4
243#endif
2441:	mov	r0, r0
245	b	1b
246ENDPROC(__error)
247