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
24 .long __bss_start @ r6
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
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.
36 * r0 = cp#15 control register
42 adr r3, __switch_data + 4
44 ldmia r3!, {r4, r5, r6, r7}
45 cmp r4, r5 @ Copy data segment if needed
51 mov fp, #0 @ Clear BSS (and zero fp)
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
65 ENDPROC(__mmap_switched)
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.
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).
77 #ifdef CONFIG_DEBUG_LL
85 str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x"
92 #ifdef CONFIG_DEBUG_LL
93 mov r4, r1 @ preserve machine ID
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
105 1: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type
109 ldr r0, [r5, #MACHINFO_NAME] @ get machine name
114 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
122 str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x"
123 str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
124 str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n"
129 #ifdef CONFIG_ARCH_RPC
131 * Turn the screen red on a error - RiscPC only.
135 orr r3, r3, r3, lsl #8
136 orr r3, r3, r3, lsl #16
148 * This provides a C-API version of __lookup_processor_type
150 ENTRY(lookup_processor_type)
151 stmfd sp!, {r4 - r6, r9, lr}
153 bl __lookup_processor_type
155 ldmfd sp!, {r4 - r6, r9, pc}
156 ENDPROC(lookup_processor_type)
159 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for
160 * more information about the __proc_info and __arch_info structures.
164 .long __arch_info_begin
165 .long __arch_info_end
168 * Lookup machine architecture in the linker-build list of architectures.
169 * Note that we can't use the absolute addresses for the __arch_info
170 * lists since we aren't running with the MMU on (and therefore, we are
171 * not in the correct address space). We have to calculate the offset.
173 * r1 = machine architecture number
175 * r3, r4, r6 corrupted
176 * r5 = mach_info pointer in physical address space
178 __lookup_machine_type:
180 ldmia r3, {r4, r5, r6}
181 sub r3, r3, r4 @ get offset between virt&phys
182 add r5, r5, r3 @ convert virt addresses to
183 add r6, r6, r3 @ physical address space
184 1: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type
185 teq r3, r1 @ matches loader number?
187 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
190 mov r5, #0 @ unknown machine
192 ENDPROC(__lookup_machine_type)
195 * This provides a C-API version of the above function.
197 ENTRY(lookup_machine_type)
198 stmfd sp!, {r4 - r6, lr}
200 bl __lookup_machine_type
202 ldmfd sp!, {r4 - r6, pc}
203 ENDPROC(lookup_machine_type)
205 /* Determine validity of the r2 atags pointer. The heuristic requires
206 * that the pointer be aligned, in the first 16k of physical RAM and
207 * that the ATAG_CORE marker is first and present. Future revisions
208 * of this function may be more lenient with the physical address and
209 * may also be able to move the ATAGS block if necessary.
214 * r2 either valid atags pointer, or zero
218 tst r2, #0x3 @ aligned?
221 ldr r5, [r2, #0] @ is first tag ATAG_CORE?
222 cmp r5, #ATAG_CORE_SIZE
223 cmpne r5, #ATAG_CORE_SIZE_EMPTY
230 mov pc, lr @ atag pointer is ok
237 * Read processor ID register (CP#15, CR0), and look up in the linker-built
238 * supported processor list. Note that we can't use the absolute addresses
239 * for the __proc_info lists since we aren't running with the MMU on
240 * (and therefore, we are not in the correct address space). We have to
241 * calculate the offset.
245 * r3, r4, r6 corrupted
246 * r5 = proc_info pointer in physical address space
247 * r9 = cpuid (preserved)
250 __lookup_processor_type:
251 adr r3, __lookup_processor_type_data
253 sub r3, r3, r4 @ get offset between virt&phys
254 add r5, r5, r3 @ convert virt addresses to
255 add r6, r6, r3 @ physical address space
256 1: ldmia r5, {r3, r4} @ value, mask
257 and r4, r4, r9 @ mask wanted bits
260 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list)
263 mov r5, #0 @ unknown processor
265 ENDPROC(__lookup_processor_type)
268 * Look in <asm/procinfo.h> for information about the __proc_info structure.
271 .type __lookup_processor_type_data, %object
272 __lookup_processor_type_data:
274 .long __proc_info_begin
275 .long __proc_info_end
276 .size __lookup_processor_type_data, . - __lookup_processor_type_data