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  *    for 32-bit CPUs which has a process ID register(CP15).
  13  *
  14  */
  15 #include <linux/config.h>
  16 #include <linux/linkage.h>
  17 #include <linux/init.h>
  18
  19 #include <asm/assembler.h>
  20 #include <asm/mach-types.h>
  21 #include <asm/procinfo.h>
  22 #include <asm/ptrace.h>
  23 #include <asm/asm-offsets.h>
  24 #include <asm/thread_info.h>
  25 #include <asm/system.h>
  26
  27 /*
  28  * Kernel startup entry point.
  29  * ---------------------------
  30  *
  31  * This is normally called from the decompressor code.  The requirements
  32  * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
  33  * r1 = machine nr.
  34  *
  35  * See linux/arch/arm/tools/mach-types for the complete list of machine
  36  * numbers for r1.
  37  *
  38  */
  39         __INIT
  40         .type   stext, %function
  41 ENTRY(stext)
  42         msr     cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC @ ensure svc mode
  43                                                 @ and irqs disabled
  44         mrc     p15, 0, r9, c0, c0              @ get processor id
  45         bl      __lookup_processor_type         @ r5=procinfo r9=cpuid
  46         movs    r10, r5                         @ invalid processor (r5=0)?
  47         beq     __error_p                               @ yes, error 'p'
  48         bl      __lookup_machine_type           @ r5=machinfo
  49         movs    r8, r5                          @ invalid machine (r5=0)?
  50         beq     __error_a                       @ yes, error 'a'
  51
  52         ldr     r13, __switch_data              @ address to jump to after
  53                                                 @ the initialization is done
  54         adr     lr, __after_proc_init           @ return (PIC) address
  55         add     pc, r10, #PROCINFO_INITFUNC
  56
  57 /*
  58  * Set the Control Register and Read the process ID.
  59  */
  60         .type   __after_proc_init, %function
  61 __after_proc_init:
  62         mrc     p15, 0, r0, c1, c0, 0           @ read control reg
  63 #ifdef CONFIG_ALIGNMENT_TRAP
  64         orr     r0, r0, #CR_A
  65 #else
  66         bic     r0, r0, #CR_A
  67 #endif
  68 #ifdef CONFIG_CPU_DCACHE_DISABLE
  69         bic     r0, r0, #CR_C
  70 #endif
  71 #ifdef CONFIG_CPU_BPREDICT_DISABLE
  72         bic     r0, r0, #CR_Z
  73 #endif
  74 #ifdef CONFIG_CPU_ICACHE_DISABLE
  75         bic     r0, r0, #CR_I
  76 #endif
  77         mcr     p15, 0, r0, c1, c0, 0           @ write control reg
  78
  79         mov     pc, r13                         @ clear the BSS and jump
  80                                                 @ to start_kernel
  81         .ltorg
  82
  83 #include "head-common.S"