source: soft/giet_vm/boot/reset.S @ 166

/********************************************************************************/
/*      File : reset.S                                                              */
/*      Author : Alain Greiner  & Mohamed karaoui                                   */
/*      Date : 03/06/2012                                                                                       */
/********************************************************************************/
/* This boot code is for a multi-cluster, multi-processor architecture,             */
/* running one or several multi-tasks software application(s) defined in        */
/* the mapping_info data-structure.                                                                     */
/* Procesor 0 uses the mapping_info data structure to build all page tables     */
/* before jumping to the kernel_init code.                                                                              */
/* Other processors are waiting until the mapping_info signature has been       */
/* modified by processor 0 (done while executing kernel_init code).             */
/* Implementation note:                                                                                                                 */
/* The entry point is 0xbfc00000, but the actual boot code starts at address    */
/* 0xbfc00500, and a minimal boot exception handler is implemented at address   */
/* 0xbfc0380.                                                                                                   */
/********************************************************************************/
                
#include <giet_config.h>
#include "../sys/mips32_registers.h"

#define EXCEP_ORG               0x380
#define START_ORG               0x500

#define OUT_MAPPING_SIGNATURE   0xBABEF00D

        .section .boot,"ax",@progbits
        .align  2
        .set noreorder

/********************************************************/
/* reset entry point                                    */
/* (address 0xBFC00000 imposed by the hardware)         */
/********************************************************/
boot_reset:
    j   boot_start
        nop

/*******************************************************/
/* handling exceptions in the boot phase               */
/* (address 0xBFC00380 imposed by the hardware         */
/*******************************************************/
        .align  2
    .org        EXCEP_ORG
boot_excep:
    la  a0,     boot_error_string
    jal boot_puts
    nop
    mfc0        a0,     CP0_TIME
        jal     boot_putw
        nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        la      a0,     boot_pid_string
    jal boot_puts
    nop
    mfc0        k0,     CP0_PROCID
    andi        a0,     k0,     0xFFF
        jal     boot_putw
    nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        la      a0,     boot_epc_string
    jal boot_puts
    nop
    mfc0        a0,     CP0_EPC
        jal     boot_putw
    nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        la      a0,     boot_cr_string
    jal boot_puts
    nop
    mfc0        a0,     CP0_CR
        jal     boot_putw
    nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        la      a0,     boot_sr_string
    jal boot_puts
    nop
    mfc0        a0,     CP0_SR
        jal     boot_putw
    nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        la      a0,     boot_bar_string
    jal boot_puts
    nop
    mfc0        a0,     CP0_BAR
        jal     boot_putw
    nop
    la  a0,     boot_lf_string
    jal boot_puts
    nop

        j       boot_exit
        nop

/*******************************************/
/* actual starting point for the boot code */
/*******************************************/
    .align      2
    .org        START_ORG

boot_start:
    /* get the procid */
    mfc0        k0,     CP0_PROCID
    andi        k0,     k0,     0xFFF   /* no more than 4096 processors... */

    /* Only processor 0 does init */
    bne k0,     zero,   boot_wait_signature
    nop

    /* Processor 0 get a temporary stack */
    la      sp, seg_boot_stack_base
    addiu       sp,     sp,     0x3000                          /* SP <= seg_boot_stack + 12K */

    /* Processor 0 initialises all Page Tables */
    jal boot_pt_init
    nop
 
    /* jump to kernel_init */
    j           boot_to_kernel_init
    nop

boot_wait_signature:

    /* all other processors are waiting signature change */
    la  k0, seg_mapping_base
    cache   0x11,   0(k0)                               /* invalidate local cache copy */
    lw  k0, 0(k0)                                               /* k0 <= mapping_info[0]       */
    li  k1,     OUT_MAPPING_SIGNATURE
    bne k1, k0, boot_wait_signature
    nop
        
    /* all other processors get a temporary stack of 256 bytes */
    la      sp, seg_boot_stack_base
    addiu   sp, sp, 0x3100                              
    mfc0        k0, CP0_PROCID
    andi    k0, k0, 0xFFF
    sll     k0, k0, 8                                   
    addu    sp, sp, k0          /* SP <= seg_boot_stack_base + 12K + (pid+1)*256 */

boot_to_kernel_init:

    /* all processors initialize PTPR with PTAB[0] */
    la      k1, _ptabs
    lw      k1, 0(k1)   
    srl     k1, k1, 13
    mtc2        k1,     CP2_PTPR                /* PTPR <= _ptabs[0]  */

        /* all processors activate MMU */
    li      k1, 0xF
    mtc2    k1, CP2_MODE        /* MODE register */

    /* jump to kernel_init */
    la      k0, seg_kernel_init_base
    j       k0
    nop

boot_error_string:      .asciiz "\n[BOOT] Fatal Error in reset.S at cycle "
boot_pid_string:        .asciiz "    PID  = "
boot_sr_string:         .asciiz "    SR   = "
boot_cr_string:         .asciiz "    CR   = "
boot_epc_string:        .asciiz "    EPC  = "
boot_bar_string:        .asciiz "    BAR  = "
boot_lf_string:         .asciiz "\n"

        .set    reorder