1 /* Modified by Broadcom Corp. Portions Copyright (c) Broadcom Corp, 2012. */
3 * linux/arch/arm/kernel/head-common.S
5 * Copyright (C) 1994-2002 Russell King
6 * Copyright (c) 2003 ARM Limited
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
15 #define ATAG_CORE 0x54410001
16 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
17 #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
20 .type __switch_data, %object
25 .long __bss_start @ r6
27 .long processor_id @ r4
28 .long __machine_arch_type @ r5
29 .long __atags_pointer @ r6
30 .long cr_alignment @ r7
31 .long init_thread_union + THREAD_START_SP @ sp
34 * The following fragment of code is executed with the MMU on in MMU mode,
35 * and uses absolute addresses; this is not position independent.
37 * r0 = cp#15 control register
43 adr r3, __switch_data + 4
45 ldmia r3!, {r4, r5, r6, r7}
46 cmp r4, r5 @ Copy data segment if needed
52 mov fp, #0 @ Clear BSS (and zero fp)
57 ARM( ldmia r3, {r4, r5, r6, r7, sp})
58 THUMB( ldmia r3, {r4, r5, r6, r7} )
59 THUMB( ldr sp, [r3, #16] )
60 str r9, [r4] @ Save processor ID
61 str r1, [r5] @ Save machine type
62 str r2, [r6] @ Save atags pointer
63 bic r4, r0, #CR_A @ Clear 'A' bit
64 stmia r7, {r0, r4} @ Save control register values
66 ENDPROC(__mmap_switched)
69 * Exception handling. Something went wrong and we can't proceed. We
70 * ought to tell the user, but since we don't have any guarantee that
71 * we're even running on the right architecture, we do virtually nothing.
73 * If CONFIG_DEBUG_LL is set we try to print out something about the error
74 * and hope for the best (useful if bootloader fails to pass a proper
75 * machine ID for example).
78 #ifdef CONFIG_DEBUG_LL
86 str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x"
93 #ifdef CONFIG_DEBUG_LL
94 mov r4, r1 @ preserve machine ID
102 ldmia r3, {r4, r5, r6} @ get machine desc list
103 sub r4, r3, r4 @ get offset between virt&phys
104 add r5, r5, r4 @ convert virt addresses to
105 add r6, r6, r4 @ physical address space
106 1: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type
110 ldr r0, [r5, #MACHINFO_NAME] @ get machine name
115 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
123 str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x"
124 str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
125 str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n"
130 #ifdef CONFIG_ARCH_RPC
132 * Turn the screen red on a error - RiscPC only.
136 orr r3, r3, r3, lsl #8
137 orr r3, r3, r3, lsl #16
149 * Read processor ID register (CP#15, CR0), and look up in the linker-built
150 * supported processor list. Note that we can't use the absolute addresses
151 * for the __proc_info lists since we aren't running with the MMU on
152 * (and therefore, we are not in the correct address space). We have to
153 * calculate the offset.
157 * r3, r4, r6 corrupted
158 * r5 = proc_info pointer in physical address space
159 * r9 = cpuid (preserved)
161 __lookup_processor_type:
165 sub r3, r3, r7 @ get offset between virt&phys
166 add r5, r5, r3 @ convert virt addresses to
167 add r6, r6, r3 @ physical address space
168 1: ldmia r5, {r3, r4} @ value, mask
169 and r4, r4, r9 @ mask wanted bits
172 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list)
175 mov r5, #0 @ unknown processor
177 ENDPROC(__lookup_processor_type)
180 * This provides a C-API version of the above function.
182 ENTRY(lookup_processor_type)
183 stmfd sp!, {r4 - r7, r9, lr}
185 bl __lookup_processor_type
187 ldmfd sp!, {r4 - r7, r9, pc}
188 ENDPROC(lookup_processor_type)
191 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for
192 * more information about the __proc_info and __arch_info structures.
195 3: .long __proc_info_begin
196 .long __proc_info_end
198 .long __arch_info_begin
199 .long __arch_info_end
202 * Lookup machine architecture in the linker-build list of architectures.
203 * Note that we can't use the absolute addresses for the __arch_info
204 * lists since we aren't running with the MMU on (and therefore, we are
205 * not in the correct address space). We have to calculate the offset.
207 * r1 = machine architecture number
209 * r3, r4, r6 corrupted
210 * r5 = mach_info pointer in physical address space
212 __lookup_machine_type:
214 ldmia r3, {r4, r5, r6}
215 sub r3, r3, r4 @ get offset between virt&phys
216 add r5, r5, r3 @ convert virt addresses to
217 add r6, r6, r3 @ physical address space
218 1: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type
219 teq r3, r1 @ matches loader number?
221 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
224 mov r5, #0 @ unknown machine
226 ENDPROC(__lookup_machine_type)
229 * This provides a C-API version of the above function.
231 ENTRY(lookup_machine_type)
232 stmfd sp!, {r4 - r6, lr}
234 bl __lookup_machine_type
236 ldmfd sp!, {r4 - r6, pc}
237 ENDPROC(lookup_machine_type)
239 /* Determine validity of the r2 atags pointer. The heuristic requires
240 * that the pointer be aligned, in the first 16k of physical RAM and
241 * that the ATAG_CORE marker is first and present. Future revisions
242 * of this function may be more lenient with the physical address and
243 * may also be able to move the ATAGS block if necessary.
248 * r2 either valid atags pointer, or zero
252 tst r2, #0x3 @ aligned?
255 ldr r5, [r2, #0] @ is first tag ATAG_CORE?
256 cmp r5, #ATAG_CORE_SIZE
257 cmpne r5, #ATAG_CORE_SIZE_EMPTY
264 mov pc, lr @ atag pointer is ok