/*
 *  linux/arch/arm/kernel/head-common.S
 *
 *  Copyright (C) 1994-2002 Russell King
 *  Copyright (c) 2003 ARM Limited
 *  All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */
#include <asm/assembler.h>

#define ATAG_CORE 0x54410001
#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)

#ifdef CONFIG_CPU_BIG_ENDIAN
#define OF_DT_MAGIC 0xd00dfeed
#else
#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
#endif

/*
 * Exception handling.  Something went wrong and we can't proceed.  We
 * ought to tell the user, but since we don't have any guarantee that
 * we're even running on the right architecture, we do virtually nothing.
 *
 * If CONFIG_DEBUG_LL is set we try to print out something about the error
 * and hope for the best (useful if bootloader fails to pass a proper
 * machine ID for example).
 */
        __HEAD

/* Determine validity of the r2 atags pointer.  The heuristic requires
 * that the pointer be aligned, in the first 16k of physical RAM and
 * that the ATAG_CORE marker is first and present.  If CONFIG_OF_FLATTREE
 * is selected, then it will also accept a dtb pointer.  Future revisions
 * of this function may be more lenient with the physical address and
 * may also be able to move the ATAGS block if necessary.
 *
 * Returns:
 *  r2 either valid atags pointer, valid dtb pointer, or zero
 *  r5, r6 corrupted
 */
__vet_atags:
        tst     r2, #0x3                        @ aligned?
        bne     1f

        ldr     r5, [r2, #0]
#ifdef CONFIG_OF_FLATTREE
        ldr     r6, =OF_DT_MAGIC                @ is it a DTB?
        cmp     r5, r6
        beq     2f
#endif
        cmp     r5, #ATAG_CORE_SIZE             @ is first tag ATAG_CORE?
        cmpne   r5, #ATAG_CORE_SIZE_EMPTY
        bne     1f
        ldr     r5, [r2, #4]
        ldr     r6, =ATAG_CORE
        cmp     r5, r6
        bne     1f

2:      ret     lr                              @ atag/dtb pointer is ok

1:      mov     r2, #0
        ret     lr
ENDPROC(__vet_atags)

/*
 * The following fragment of code is executed with the MMU on in MMU mode,
 * and uses absolute addresses; this is not position independent.
 *
 *  r0  = cp#15 control register
 *  r1  = machine ID
 *  r2  = atags/dtb pointer
 *  r9  = processor ID
 */
        __INIT
__mmap_switched:
        adr     r3, __mmap_switched_data

        ldmia   r3!, {r4, r5, r6, r7}
        cmp     r4, r5                          @ Copy data segment if needed
1:      cmpne   r5, r6
        ldrne   fp, [r4], #4
        strne   fp, [r5], #4
        bne     1b

        mov     fp, #0                          @ Clear BSS (and zero fp)
1:      cmp     r6, r7
        strcc   fp, [r6],#4
        bcc     1b

 ARM(   ldmia   r3, {r4, r5, r6, r7, sp})
 THUMB( ldmia   r3, {r4, r5, r6, r7}    )
 THUMB( ldr     sp, [r3, #16]           )
        str     r9, [r4]                        @ Save processor ID
        str     r1, [r5]                        @ Save machine type
        str     r2, [r6]                        @ Save atags pointer
        cmp     r7, #0
        strne   r0, [r7]                        @ Save control register values
        b       start_kernel
ENDPROC(__mmap_switched)

        .align  2
        .type   __mmap_switched_data, %object
__mmap_switched_data:
        .long   __data_loc                      @ r4
        .long   _sdata                          @ r5
        .long   __bss_start                     @ r6
        .long   _end                            @ r7
        .long   processor_id                    @ r4
        .long   __machine_arch_type             @ r5
        .long   __atags_pointer                 @ r6
#ifdef CONFIG_CPU_CP15
        .long   cr_alignment                    @ r7
#else
        .long   0                               @ r7
#endif
        .long   init_thread_union + THREAD_START_SP @ sp
        .size   __mmap_switched_data, . - __mmap_switched_data

/*
 * This provides a C-API version of __lookup_processor_type
 */
ENTRY(lookup_processor_type)
        stmfd   sp!, {r4 - r6, r9, lr}
        mov     r9, r0
        bl      __lookup_processor_type
        mov     r0, r5
        ldmfd   sp!, {r4 - r6, r9, pc}
ENDPROC(lookup_processor_type)

        __FINIT
        .text

/*
 * Read processor ID register (CP#15, CR0), and look up in the linker-built
 * supported processor list.  Note that we can't use the absolute addresses
 * for the __proc_info lists since we aren't running with the MMU on
 * (and therefore, we are not in the correct address space).  We have to
 * calculate the offset.
 *
 *      r9 = cpuid
 * Returns:
 *      r3, r4, r6 corrupted
 *      r5 = proc_info pointer in physical address space
 *      r9 = cpuid (preserved)
 */
__lookup_processor_type:
        adr     r3, __lookup_processor_type_data
        ldmia   r3, {r4 - r6}
        sub     r3, r3, r4                      @ get offset between virt&phys
        add     r5, r5, r3                      @ convert virt addresses to
        add     r6, r6, r3                      @ physical address space
1:      ldmia   r5, {r3, r4}                    @ value, mask
        and     r4, r4, r9                      @ mask wanted bits
        teq     r3, r4
        beq     2f
        add     r5, r5, #PROC_INFO_SZ           @ sizeof(proc_info_list)
        cmp     r5, r6
        blo     1b
        mov     r5, #0                          @ unknown processor
2:      ret     lr
ENDPROC(__lookup_processor_type)

/*
 * Look in <asm/procinfo.h> for information about the __proc_info structure.
 */
        .align  2
        .type   __lookup_processor_type_data, %object
__lookup_processor_type_data:
        .long   .
        .long   __proc_info_begin
        .long   __proc_info_end
        .size   __lookup_processor_type_data, . - __lookup_processor_type_data

__error_lpae:
#ifdef CONFIG_DEBUG_LL
        adr     r0, str_lpae
        bl      printascii
        b       __error
str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
#else
        b       __error
#endif
        .align
ENDPROC(__error_lpae)

__error_p:
#ifdef CONFIG_DEBUG_LL
        adr     r0, str_p1
        bl      printascii
        mov     r0, r9
        bl      printhex8
        adr     r0, str_p2
        bl      printascii
        b       __error
str_p1: .asciz  "\nError: unrecognized/unsupported processor variant (0x"
str_p2: .asciz  ").\n"
        .align
#endif
ENDPROC(__error_p)

__error:
#ifdef CONFIG_ARCH_RPC
/*
 * Turn the screen red on a error - RiscPC only.
 */
        mov     r0, #0x02000000
        mov     r3, #0x11
        orr     r3, r3, r3, lsl #8
        orr     r3, r3, r3, lsl #16
        str     r3, [r0], #4
        str     r3, [r0], #4
        str     r3, [r0], #4
        str     r3, [r0], #4
#endif
1:      mov     r0, r0
        b       1b
ENDPROC(__error)