2 * linux/arch/arm/kernel/head-common.S
4 * Copyright (C) 1994-2002 Russell King
5 * Copyright (c) 2003 ARM Limited
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.
14 #define ATAG_CORE 0x54410001
15 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
16 #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
19 .type __switch_data, %object
23 .long __bss_start @ r6
25 .long processor_id @ r4
26 .long __machine_arch_type @ r5
27 .long __atags_pointer @ r6
28 .long cr_alignment @ r7
29 .long init_thread_union + THREAD_START_SP @ sp
32 * The following fragment of code is executed with the MMU on in MMU mode,
33 * and uses absolute addresses; this is not position independent.
35 * r0 = cp#15 control register
43 ldmia r3!, {r4, r5, r6, r7}
44 cmp r4, r5 @ Copy data segment if needed
50 mov fp, #0 @ Clear BSS (and zero fp)
55 ARM( ldmia r3, {r4, r5, r6, r7, sp})
56 THUMB( ldmia r3, {r4, r5, r6, r7} )
57 THUMB( ldr sp, [r3, #16] )
58 str r9, [r4] @ Save processor ID
59 str r1, [r5] @ Save machine type
60 str r2, [r6] @ Save atags pointer
61 bic r4, r0, #CR_A @ Clear 'A' bit
62 stmia r7, {r0, r4} @ Save control register values
64 ENDPROC(__mmap_switched)
67 * Exception handling. Something went wrong and we can't proceed. We
68 * ought to tell the user, but since we don't have any guarantee that
69 * we're even running on the right architecture, we do virtually nothing.
71 * If CONFIG_DEBUG_LL is set we try to print out something about the error
72 * and hope for the best (useful if bootloader fails to pass a proper
73 * machine ID for example).
76 #ifdef CONFIG_DEBUG_LL
84 str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x"
91 #ifdef CONFIG_DEBUG_LL
92 mov r4, r1 @ preserve machine ID
100 ldmia r3, {r4, r5, r6} @ get machine desc list
101 sub r4, r3, r4 @ get offset between virt&phys
102 add r5, r5, r4 @ convert virt addresses to
103 add r6, r6, r4 @ physical address space
104 1: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type
108 ldr r0, [r5, #MACHINFO_NAME] @ get machine name
113 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
121 str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x"
122 str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
123 str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n"
128 #ifdef CONFIG_ARCH_RPC
130 * Turn the screen red on a error - RiscPC only.
134 orr r3, r3, r3, lsl #8
135 orr r3, r3, r3, lsl #16
147 * This provides a C-API version of __lookup_processor_type
149 ENTRY(lookup_processor_type)
150 stmfd sp!, {r4 - r6, r9, lr}
152 bl __lookup_processor_type
154 ldmfd sp!, {r4 - r6, r9, pc}
155 ENDPROC(lookup_processor_type)
158 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for
159 * more information about the __proc_info and __arch_info structures.
163 .long __arch_info_begin
164 .long __arch_info_end
167 * Lookup machine architecture in the linker-build list of architectures.
168 * Note that we can't use the absolute addresses for the __arch_info
169 * lists since we aren't running with the MMU on (and therefore, we are
170 * not in the correct address space). We have to calculate the offset.
172 * r1 = machine architecture number
174 * r3, r4, r6 corrupted
175 * r5 = mach_info pointer in physical address space
177 __lookup_machine_type:
179 ldmia r3, {r4, r5, r6}
180 sub r3, r3, r4 @ get offset between virt&phys
181 add r5, r5, r3 @ convert virt addresses to
182 add r6, r6, r3 @ physical address space
183 1: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type
184 teq r3, r1 @ matches loader number?
186 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
189 mov r5, #0 @ unknown machine
191 ENDPROC(__lookup_machine_type)
194 * This provides a C-API version of the above function.
196 ENTRY(lookup_machine_type)
197 stmfd sp!, {r4 - r6, lr}
199 bl __lookup_machine_type
201 ldmfd sp!, {r4 - r6, pc}
202 ENDPROC(lookup_machine_type)
204 /* Determine validity of the r2 atags pointer. The heuristic requires
205 * that the pointer be aligned, in the first 16k of physical RAM and
206 * that the ATAG_CORE marker is first and present. Future revisions
207 * of this function may be more lenient with the physical address and
208 * may also be able to move the ATAGS block if necessary.
213 * r2 either valid atags pointer, or zero
217 tst r2, #0x3 @ aligned?
220 ldr r5, [r2, #0] @ is first tag ATAG_CORE?
221 cmp r5, #ATAG_CORE_SIZE
222 cmpne r5, #ATAG_CORE_SIZE_EMPTY
229 mov pc, lr @ atag pointer is ok
236 * Read processor ID register (CP#15, CR0), and look up in the linker-built
237 * supported processor list. Note that we can't use the absolute addresses
238 * for the __proc_info lists since we aren't running with the MMU on
239 * (and therefore, we are not in the correct address space). We have to
240 * calculate the offset.
244 * r3, r4, r6 corrupted
245 * r5 = proc_info pointer in physical address space
246 * r9 = cpuid (preserved)
249 __lookup_processor_type:
250 adr r3, __lookup_processor_type_data
252 sub r3, r3, r4 @ get offset between virt&phys
253 add r5, r5, r3 @ convert virt addresses to
254 add r6, r6, r3 @ physical address space
255 1: ldmia r5, {r3, r4} @ value, mask
256 and r4, r4, r9 @ mask wanted bits
259 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list)
262 mov r5, #0 @ unknown processor
264 ENDPROC(__lookup_processor_type)
267 * Look in <asm/procinfo.h> for information about the __proc_info structure.
270 .type __lookup_processor_type_data, %object
271 __lookup_processor_type_data:
273 .long __proc_info_begin
274 .long __proc_info_end
275 .size __lookup_processor_type_data, . - __lookup_processor_type_data