arch/arm/kernel/head-common.S

   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
  14 #define ATAG_CORE 0x54410001
  15 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
  16 #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
  17
  18 #ifdef CONFIG_CPU_BIG_ENDIAN
  19 #define OF_DT_MAGIC 0xd00dfeed
  20 #else
  21 #define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
  22 #endif
  23
  24 /*
  25  * Exception handling.  Something went wrong and we can't proceed.  We
  26  * ought to tell the user, but since we don't have any guarantee that
  27  * we're even running on the right architecture, we do virtually nothing.
  28  *
  29  * If CONFIG_DEBUG_LL is set we try to print out something about the error
  30  * and hope for the best (useful if bootloader fails to pass a proper
  31  * machine ID for example).
  32  */
  33         __HEAD
  34
  35 /* Determine validity of the r2 atags pointer.  The heuristic requires
  36  * that the pointer be aligned, in the first 16k of physical RAM and
  37  * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
  38  * is selected, then it will also accept a dtb pointer.  Future revisions
  39  * of this function may be more lenient with the physical address and
  40  * may also be able to move the ATAGS block if necessary.
  41  *
  42  * Returns:
  43  *  r2 either valid atags pointer, valid dtb pointer, or zero
  44  *  r5, r6 corrupted
  45  */
  46 __vet_atags:
  47         tst     r2, #0x3                        @ aligned?
  48         bne     1f
  49
  50         ldr     r5, [r2, #0]
  51 #ifdef CONFIG_OF_FLATTREE
  52         ldr     r6, =OF_DT_MAGIC                @ is it a DTB?
  53         cmp     r5, r6
  54         beq     2f
  55 #endif
  56         cmp     r5, #ATAG_CORE_SIZE             @ is first tag ATAG_CORE?
  57         cmpne   r5, #ATAG_CORE_SIZE_EMPTY
  58         bne     1f
  59         ldr     r5, [r2, #4]
  60         ldr     r6, =ATAG_CORE
  61         cmp     r5, r6
  62         bne     1f
  63
  64 2:      mov     pc, lr                          @ atag/dtb pointer is ok
  65
  66 1:      mov     r2, #0
  67         mov     pc, lr
  68 ENDPROC(__vet_atags)
  69
  70 /*
  71  * The following fragment of code is executed with the MMU on in MMU mode,
  72  * and uses absolute addresses; this is not position independent.
  73  *
  74  *  r0  = cp#15 control register
  75  *  r1  = machine ID
  76  *  r2  = atags/dtb pointer
  77  *  r9  = processor ID
  78  */
  79         __INIT
  80 __mmap_switched:
  81         adr     r3, __mmap_switched_data
  82
  83         ldmia   r3!, {r4, r5, r6, r7}
  84         cmp     r4, r5                          @ Copy data segment if needed
  85 1:      cmpne   r5, r6
  86         ldrne   fp, [r4], #4
  87         strne   fp, [r5], #4
  88         bne     1b
  89
  90         mov     fp, #0                          @ Clear BSS (and zero fp)
  91 1:      cmp     r6, r7
  92         strcc   fp, [r6],#4
  93         bcc     1b
  94
  95  ARM(   ldmia   r3, {r4, r5, r6, r7, sp})
  96  THUMB( ldmia   r3, {r4, r5, r6, r7}    )
  97  THUMB( ldr     sp, [r3, #16]           )
  98         str     r9, [r4]                        @ Save processor ID
  99         str     r1, [r5]                        @ Save machine type
 100         str     r2, [r6]                        @ Save atags pointer
 101         bic     r4, r0, #CR_A                   @ Clear 'A' bit
 102         stmia   r7, {r0, r4}                    @ Save control register values
 103         b       start_kernel
 104 ENDPROC(__mmap_switched)
 105
 106         .align  2
 107         .type   __mmap_switched_data, %object
 108 __mmap_switched_data:
 109         .long   __data_loc                      @ r4
 110         .long   _sdata                          @ r5
 111         .long   __bss_start                     @ r6
 112         .long   _end                            @ r7
 113         .long   processor_id                    @ r4
 114         .long   __machine_arch_type             @ r5
 115         .long   __atags_pointer                 @ r6
 116         .long   cr_alignment                    @ r7
 117         .long   init_thread_union + THREAD_START_SP @ sp
 118         .size   __mmap_switched_data, . - __mmap_switched_data
 119
 120 /*
 121  * This provides a C-API version of __lookup_processor_type
 122  */
 123 ENTRY(lookup_processor_type)
 124         stmfd   sp!, {r4 - r6, r9, lr}
 125         mov     r9, r0
 126         bl      __lookup_processor_type
 127         mov     r0, r5
 128         ldmfd   sp!, {r4 - r6, r9, pc}
 129 ENDPROC(lookup_processor_type)
 130
 131 /*
 132  * Read processor ID register (CP#15, CR0), and look up in the linker-built
 133  * supported processor list.  Note that we can't use the absolute addresses
 134  * for the __proc_info lists since we aren't running with the MMU on
 135  * (and therefore, we are not in the correct address space).  We have to
 136  * calculate the offset.
 137  *
 138  *      r9 = cpuid
 139  * Returns:
 140  *      r3, r4, r6 corrupted
 141  *      r5 = proc_info pointer in physical address space
 142  *      r9 = cpuid (preserved)
 143  */
 144         __CPUINIT
 145 __lookup_processor_type:
 146         adr     r3, __lookup_processor_type_data
 147         ldmia   r3, {r4 - r6}
 148         sub     r3, r3, r4                      @ get offset between virt&phys
 149         add     r5, r5, r3                      @ convert virt addresses to
 150         add     r6, r6, r3                      @ physical address space
 151 1:      ldmia   r5, {r3, r4}                    @ value, mask
 152         and     r4, r4, r9                      @ mask wanted bits
 153         teq     r3, r4
 154         beq     2f
 155         add     r5, r5, #PROC_INFO_SZ           @ sizeof(proc_info_list)
 156         cmp     r5, r6
 157         blo     1b
 158         mov     r5, #0                          @ unknown processor
 159 2:      mov     pc, lr
 160 ENDPROC(__lookup_processor_type)
 161
 162 /*
 163  * Look in <asm/procinfo.h> for information about the __proc_info structure.
 164  */
 165         .align  2
 166         .type   __lookup_processor_type_data, %object
 167 __lookup_processor_type_data:
 168         .long   .
 169         .long   __proc_info_begin
 170         .long   __proc_info_end
 171         .size   __lookup_processor_type_data, . - __lookup_processor_type_data
 172
 173 __error_p:
 174 #ifdef CONFIG_DEBUG_LL
 175         adr     r0, str_p1
 176         bl      printascii
 177         mov     r0, r9
 178         bl      printhex8
 179         adr     r0, str_p2
 180         bl      printascii
 181         b       __error
 182 str_p1: .asciz  "\nError: unrecognized/unsupported processor variant (0x"
 183 str_p2: .asciz  ").\n"
 184         .align
 185 #endif
 186 ENDPROC(__error_p)
 187
 188 __error:
 189 #ifdef CONFIG_ARCH_RPC
 190 /*
 191  * Turn the screen red on a error - RiscPC only.
 192  */
 193         mov     r0, #0x02000000
 194         mov     r3, #0x11
 195         orr     r3, r3, r3, lsl #8
 196         orr     r3, r3, r3, lsl #16
 197         str     r3, [r0], #4
 198         str     r3, [r0], #4
 199         str     r3, [r0], #4
 200         str     r3, [r0], #4
 201 #endif
 202 1:      mov     r0, r0
 203         b       1b
 204 ENDPROC(__error)