start.s

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*
** start.S -- startup file for Mongoose V BSP based upon crt0.S from
** newlib-1.8.2/libgloss/mips and adapted for RTEMS.
**
** crt0.S -- startup file for MIPS.
**
** Copyright (c) 1995, 1996, 1997 Cygnus Support
**
** The authors hereby grant permission to use, copy, modify, distribute,
** and license this software and its documentation for any purpose, provided
** that existing copyright notices are retained in all copies and that this
** notice is included verbatim in any distributions. No written agreement,
** license, or royalty fee is required for any of the authorized uses.
** Modifications to this software may be copyrighted by their authors
** and need not follow the licensing terms described here, provided that
** the new terms are clearly indicated on the first page of each file where
** they apply.
**
**
** Modification History:
**        01/XX/01  Joel Sherrill, OAR Corp,
**           Modified for Mongoose V BSP for NASA/GSFC Code 582.
**
**        06/XX/01  Greg Menke, Raytheon, Code 582
**           Debug modifications. Removed R4000 dependencies.
**           Added HACKED_PMON defines to facilitate startup.
**           Added DEFAULT_EXIT_RETURN_TO_MONITOR option.
**
**        11/14/01  A.Ferrer, NASA/GSFC, Code 582
**           Cleanup for ST5 mission.
**
**        11/27/01  A.Ferrer, NASA/GSFC, Code 582
**           Added cache flush routines.
*/

#ifndef LANGUAGE_ASSEMBLY
#define LANGUAGE_ASSEMBLY
#endif


#include <asm.h>
#include "regs.S"
#include "mg5.h"


	
#ifdef __mips16
   /* This file contains 32 bit assembly code.  */
   .set nomips16
#endif


/*
** defined by linkcmds, pointing to the start of the relocation target
** memory, referenced in this way so we can avoid defining it
** multiply
*/
   .bss
   .word 0
   .text
   .align 2


/**********************************************************************
**
** Function: _start
*/

   /* Without the following nop, GDB thinks _start is a data variable.
   ** This is probably a bug in GDB in handling a symbol that is at the
   ** start of the .text section.
   */
    nop
   .globl  _start
   .ent    _start

   .globl putch_rom
_start:
   .set    noreorder
   $LF1 = . + 8

   /*
   ** Get the address of start into $5 in a position independent fashion.
   ** This lets us know whether we have been relocated or not.
   */

   bal     $LF1
   nop
_branch:
   move    a1, ra      /* save return address from the jump above */

   /* ensure we're sane before doing anything */

   li      t0, SR_CU0|SR_PE
   mtc0    t0, C0_SR
   nop
   li      t0, 0
   mtc0    t0, C0_DCIC
   nop
   mtc0    t0, C0_CAUSE
   nop


   /*
   ** Call cpuinit. Masking used to call EEPROM address of _cpuinit.  Label is RAM label.
   */
   move   t2,a1
   and    t2,0xffff0000
   la     t0,_cpuinit
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   /*
   ** Configure UART
   */
   move   t2,a1
   and    t2,0xffff0000
   la     t0,config_uart
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop



   /*
   ** Print 'b'.  Show that we started.
   */
   move   t2,a1
   and    t2,0xffff0000
   li     a0,'b'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop
	

			
		

   li	k0,0
   li   k1,0
	
   move t1,a1
   nop
   li	t2,0xa0000000	/* lower limit of kseg1 */
   li   t3,0xbfffffff	/* upper limit of kseg1 */

   subu	t0,t1,t2
   srl  t0,31		/* shift high bit down to bit 0 */
   bnez t0,1f		/* booting from below kseg1 */
	
   subu t0,t3,t1
   srl  t0,31		/* shift high bit down to bit 0 */
   bnez t0,1f		/* booting from above kseg1 */

		
	
   /*
   ** Call IcacheFlush. Masking used to call EEPROM address of IcacheFlush.  Label is RAM label.
   */
   move   t2,a1
   and    t2,0xffff0000
   la     t0,IcacheFlush
   and    t0,0x0000ffff
   or     t0,t2
   move	  k0,t0		/* save cache flush in-prom address */
   jal    t0
   nop


   /*
   ** Print 'I'.  Show that we flushed I cache.
   */
   move   t2,a1
   and    t2,0xffff0000
   li     a0,'I'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop


   /*
   ** Call DcacheFlush. Masking used to call EEPROM address of DcacheFlush.  Label is RAM label.
   */
   move   t2,a1
   and    t2,0xffff0000
   la     t0,DcacheFlush
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop


   /*
   ** Print 'D'.  Show that we flushed D cache.
   */
   move   t2,a1
   and    t2,0xffff0000
   li     a0,'D'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   move	  k1,t0		/* save cache flush in-prom address */
   jal    t0
   nop


1:	
   /*
   ** Print ' RTEMS  b'.  Show that we are booting.
   */
   move   t2,a1
   and    t2,0xffff0000
   li     a0,' '
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'R'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'T'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'E'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'M'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'S'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,' '
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   move   t2,a1
   and    t2,0xffff0000
   li     a0,'b'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop


   /*
   ** get the address of the _branch label above as it would appear in
   ** the relocated code
   */

   la  a2, _branch                 /* relocation destination */
   beq a1, a2, _start_in_ram       /* skip relocating if we're already there */
   nop

   /* relocate the code from EEPROM to RAM */

   /*
   ** Print 'r'
   */
   move   t2,a1
   and    t2,0xffff0000
   li     a0,'r'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal	  t0
   nop

   la		a3, _edata
relocate:
   lw		t0, (a1)            /* load from EEPROM */
   addu		a1, 4
   sw		t0, (a2)            /* store to RAM */
   addu		a2, 4
   bne		a2, a3, relocate    /* copied all the way to edata? */
   nop

   /*
   ** Print 'R'
   */
   li     a0,'R'
   la     t0,putch_rom
   and    t0,0x0000ffff
   or     t0,t2
   jal    t0
   nop

   la  a2, _start_in_ram
   jr  a2
   nop
   .end _start


/**********************************************************************
**
** Function: _start_in_ram
*/

   .globl  _start_in_ram
   .ent _start_in_ram
_start_in_ram:

   /*
   ** Print 'S'.  Already in RAM no need to reference EEPROM address.
   */
   li	a0,'S'
   jal	putch_rom
   nop

   la	gp, _gp			/* set the global data pointer */
   .end _start_in_ram


/**********************************************************************
**
** Function: zerobss
*/
   .globl  __memsize
   .globl  zerobss
   .ent    zerobss
zerobss:

   /*
   ** Print 'z'.  Starting to zero out bss.
   */
   li a0,'z'
   jal putch_rom
   nop

   la		v0, _fbss
   la		v1, _end
3:
   sw		zero,0(v0)
   bltu		v0,v1,3b
   addiu	v0,v0,4               /* executed in delay slot */

   la  t0, _stack_init         /* initialize stack so we */

   /*
   ** We must subtract 24 bytes for the 3 8 byte arguments to main, in
   ** case main wants to write them back to the stack.  The caller is
   ** supposed to allocate stack space for parameters in registers in
   ** the old MIPS ABIs.  We must do this even though we aren't passing
   ** arguments, because main might be declared to have them.
   **
   ** Some ports need a larger alignment for the stack, so we subtract
   ** 32, which satisifes the stack for the arguments and keeps the
   ** stack pointer better aligned.
   */
   subu    t0,t0,32
   move    sp,t0               /* set stack pointer */
   nop

   /*
   ** Print 'Z'.  Finished zeroing bss.
   */
   li	a0,'Z'
   jal	putch_rom
   nop

   .end    zerobss


/**********************************************************************
**
** Function: _init
*/
   .globl  exit .text
   .globl  _initialize_rtems
   .ent    _initialize_rtems
_initialize_rtems:

   /*
   ** Print 'i'.  Starting to initialize RTEMS.
   */
   li		a0, 'i'
   jal		putch_rom
   nop


   /*
   ** Save the boot-time addresses of the I & D cache flush routines.
   ** Note, if we're running from RAM, we cannot manipulate the cache
   ** so we just disable the cache flush functions.
   */
   la		a0,_promIcache
   sw		k0,0(a0)
   nop
	
   la		a0,_promDcache
   sw		k1,0(a0)
   nop

   move		a0,zero         /* set argc to 0 */
   jal		boot_card           /* call the program start function */
   nop

   /*
   ** fall through to the "exit" routine
   */
   jal _sys_exit
   nop
   .end _initialize_rtems


/**********************************************************************
**
** Function: _sys_exit
**
** Exit from the application by jumping to PMON address in EEPROM.
*/
   .globl  _sys_exit
   .ent _sys_exit
_sys_exit:
   la  t0, PMON_ADDRESS
   jal t0
   .end _sys_exit



/**********************************************************************
**
** function: putch
** input   : ASCII character in A0
** registers used: ra, a0, t0, t1
**
*/