arch/arm/kernel/head-nommu.S

   1 /*
   2  *  linux/arch/arm/kernel/head-nommu.S
   3  *
   4  *  Copyright (C) 1994-2002 Russell King
   5  *  Copyright (C) 2003-2006 Hyok S. Choi
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  *  Common kernel startup code (non-paged MM)
  12  *
  13  */
  14 #include <linux/linkage.h>
  15 #include <linux/init.h>
  16
  17 #include <asm/assembler.h>
  18 #include <asm/ptrace.h>
  19 #include <asm/asm-offsets.h>
  20 #include <asm/cp15.h>
  21 #include <asm/thread_info.h>
  22
  23 /*
  24  * Kernel startup entry point.
  25  * ---------------------------
  26  *
  27  * This is normally called from the decompressor code.  The requirements
  28  * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
  29  * r1 = machine nr.
  30  *
  31  * See linux/arch/arm/tools/mach-types for the complete list of machine
  32  * numbers for r1.
  33  *
  34  */
  35
  36         __HEAD
  37
  38 #ifdef CONFIG_CPU_THUMBONLY
  39         .thumb
  40 ENTRY(stext)
  41 #else
  42         .arm
  43 ENTRY(stext)
  44
  45  THUMB( adr     r9, BSYM(1f)    )       @ Kernel is always entered in ARM.
  46  THUMB( bx      r9              )       @ If this is a Thumb-2 kernel,
  47  THUMB( .thumb                  )       @ switch to Thumb now.
  48  THUMB(1:                       )
  49 #endif
  50
  51         setmode PSR_F_BIT | PSR_I_BIT | SVC_MODE, r9 @ ensure svc mode
  52                                                 @ and irqs disabled
  53 #ifndef CONFIG_CPU_CP15
  54         ldr     r9, =CONFIG_PROCESSOR_ID
  55 #else
  56         mrc     p15, 0, r9, c0, c0              @ get processor id
  57 #endif
  58         bl      __lookup_processor_type         @ r5=procinfo r9=cpuid
  59         movs    r10, r5                         @ invalid processor (r5=0)?
  60         beq     __error_p                               @ yes, error 'p'
  61
  62         adr     lr, BSYM(__after_proc_init)     @ return (PIC) address
  63  ARM(   add     pc, r10, #PROCINFO_INITFUNC     )
  64  THUMB( add     r12, r10, #PROCINFO_INITFUNC    )
  65  THUMB( mov     pc, r12                         )
  66 ENDPROC(stext)
  67
  68 /*
  69  * Set the Control Register and Read the process ID.
  70  */
  71 __after_proc_init:
  72 #ifdef CONFIG_CPU_CP15
  73         /*
  74          * CP15 system control register value returned in r0 from
  75          * the CPU init function.
  76          */
  77 #if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
  78         orr     r0, r0, #CR_A
  79 #else
  80         bic     r0, r0, #CR_A
  81 #endif
  82 #ifdef CONFIG_CPU_DCACHE_DISABLE
  83         bic     r0, r0, #CR_C
  84 #endif
  85 #ifdef CONFIG_CPU_BPREDICT_DISABLE
  86         bic     r0, r0, #CR_Z
  87 #endif
  88 #ifdef CONFIG_CPU_ICACHE_DISABLE
  89         bic     r0, r0, #CR_I
  90 #endif
  91 #ifdef CONFIG_CPU_HIGH_VECTOR
  92         orr     r0, r0, #CR_V
  93 #else
  94         bic     r0, r0, #CR_V
  95 #endif
  96         mcr     p15, 0, r0, c1, c0, 0           @ write control reg
  97 #endif /* CONFIG_CPU_CP15 */
  98
  99         b       __mmap_switched                 @ clear the BSS and jump
 100                                                 @ to start_kernel
 101 ENDPROC(__after_proc_init)
 102         .ltorg
 103
 104 #include "head-common.S"