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/constants.h>
  24 #include <asm/system.h>
  25
  26 #define PROCINFO_INITFUNC       12
  27
  28 /*
  29  * Kernel startup entry point.
  30  * ---------------------------
  31  *
  32  * This is normally called from the decompressor code.  The requirements
  33  * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
  34  * r1 = machine nr.
  35  *
  36  * See linux/arch/arm/tools/mach-types for the complete list of machine
  37  * numbers for r1.
  38  *
  39  */
  40         __INIT
  41         .type   stext, %function
  42 ENTRY(stext)
  43         msr     cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC @ ensure svc mode
  44                                                 @ and irqs disabled
  45         mrc     p15, 0, r9, c0, c0              @ get processor id
  46         bl      __lookup_processor_type         @ r5=procinfo r9=cpuid
  47         movs    r10, r5                         @ invalid processor (r5=0)?
  48         beq     __error_p                               @ yes, error 'p'
  49         bl      __lookup_machine_type           @ r5=machinfo
  50         movs    r8, r5                          @ invalid machine (r5=0)?
  51         beq     __error_a                       @ yes, error 'a'
  52
  53         ldr     r13, __switch_data              @ address to jump to after
  54                                                 @ the initialization is done
  55         adr     lr, __after_proc_init           @ return (PIC) address
  56         add     pc, r10, #PROCINFO_INITFUNC
  57
  58 /*
  59  * Set the Control Register and Read the process ID.
  60  */
  61         .type   __after_proc_init, %function
  62 __after_proc_init:
  63         mrc     p15, 0, r0, c1, c0, 0           @ read control reg
  64 #ifdef CONFIG_ALIGNMENT_TRAP
  65         orr     r0, r0, #CR_A
  66 #else
  67         bic     r0, r0, #CR_A
  68 #endif
  69 #ifdef CONFIG_CPU_DCACHE_DISABLE
  70         bic     r0, r0, #CR_C
  71 #endif
  72 #ifdef CONFIG_CPU_BPREDICT_DISABLE
  73         bic     r0, r0, #CR_Z
  74 #endif
  75 #ifdef CONFIG_CPU_ICACHE_DISABLE
  76         bic     r0, r0, #CR_I
  77 #endif
  78         mcr     p15, 0, r0, c1, c0, 0           @ write control reg
  79
  80         mov     pc, r13                         @ clear the BSS and jump
  81                                                 @ to start_kernel
  82
  83 #include "head-common.S"