tiny_init.s

一个很好的嵌入式linux平台下的bootloader

/*  *********************************************************************
    *  SB1250 Board Support Package
    *  
    *  Board-specific initialization		File: TINY_INIT.S
    *
    *  This module contains the assembly-language part of the init
    *  code for this board support package.  The routine
    *  "board_earlyinit" lives here.
    *  
    *  Author:  Mitch Lichtenberg
    *  
    *********************************************************************  
    *
    *  Copyright 2000,2001,2002,2003
    *  Broadcom Corporation. All rights reserved.
    *  
    *  This software is furnished under license and may be used and 
    *  copied only in accordance with the following terms and 
    *  conditions.  Subject to these conditions, you may download, 
    *  copy, install, use, modify and distribute modified or unmodified 
    *  copies of this software in source and/or binary form.  No title 
    *  or ownership is transferred hereby.
    *  
    *  1) Any source code used, modified or distributed must reproduce 
    *     and retain this copyright notice and list of conditions 
    *     as they appear in the source file.
    *  
    *  2) No right is granted to use any trade name, trademark, or 
    *     logo of Broadcom Corporation.  The "Broadcom Corporation" 
    *     name may not be used to endorse or promote products derived 
    *     from this software without the prior written permission of 
    *     Broadcom Corporation.
    *  
    *  3) THIS SOFTWARE IS PROVIDED "AS-IS" AND ANY EXPRESS OR
    *     IMPLIED WARRANTIES, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED
    *     WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
    *     PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED. IN NO EVENT 
    *     SHALL BROADCOM BE LIABLE FOR ANY DAMAGES WHATSOEVER, AND IN 
    *     PARTICULAR, BROADCOM SHALL NOT BE LIABLE FOR DIRECT, INDIRECT,
    *     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
    *     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
    *     GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
    *     BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 
    *     OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR 
    *     TORT (INCLUDING NEGLIGENCE OR OTHERWISE), EVEN IF ADVISED OF 
    *     THE POSSIBILITY OF SUCH DAMAGE.
    ********************************************************************* */


#include "sbmips.h"
#include "sb1250_genbus.h"
#include "sb1250_regs.h"
#include "sb1250_scd.h"
#include "bsp_config.h"
#include "tiny.h"

		.text

/*  *********************************************************************
    *  Macros
    ********************************************************************* */



/*  *********************************************************************
    *  BOARD_EARLYINIT()
    *  
    *  Initialize board registers.  This is the earliest 
    *  time the BSP gets control.  This routine cannot assume that
    *  memory is operational, and therefore all code in this routine
    *  must run from registers only.  The $ra register must not
    *  be modified, as it contains the return address.
    *
    *  This routine will be called from uncached space, before
    *  the caches are initialized.  If you want to make
    *  subroutine calls from here, you must use the CALLKSEG1 macro.
    *
    *  Among other things, this is where the GPIO registers get 
    *  programmed to make on-board LEDs function, or other startup
    *  that has to be done before anything will work.
    *  
    *  Input parameters: 
    *  	   nothing
    *  	   
    *  Return value:
    *  	   nothing
    ********************************************************************* */

LEAF(board_earlyinit)

	#
	# Reprogram the SCD to make sure UART0 is enabled.
	# Some CSWARM boards have the SER0 enable bit when
	# they're not supposed to, which switches the UART
	# into synchronous mode.  Kill off the SCD bit.
	# XXX this should be investigated in hardware, as 
	# XXX it is a strap option on the CPU.
	#

		li      t0,PHYS_TO_K1(A_SCD_SYSTEM_CFG)
		ld	t1,0(t0)
		dli	t2,~M_SYS_SER0_ENABLE
		and	t1,t1,t2
		sd	t1,0(t0)

       #
       # Configure the GPIOs
       #

		li	t0,PHYS_TO_K1(A_GPIO_DIRECTION)
		li	t1,GPIO_OUTPUT_MASK
		sd	t1,0(t0)

		li	t0,PHYS_TO_K1(A_GPIO_INT_TYPE)
		li	t1,GPIO_INTERRUPT_MASK
		sd	t1,0(t0)

       #
       # Turn on the diagnostic LED and turn off the sturgeon NMI
       #
		li	t0,PHYS_TO_K1(A_GPIO_PIN_SET)
		li	t1,M_GPIO_DEBUG_LED
		sd	t1,0(t0)

		li	t0,PHYS_TO_K1(A_GPIO_PIN_CLR)
		li	t1,M_GPIO_STURGEON_NMI
		sd	t1,0(t0)


       #
       # Configure the LEDs
       #     

		li	t0,PHYS_TO_K1(A_IO_EXT_CS_BASE(LEDS_CS))
		li	t1,LEDS_PHYS >> S_IO_ADDRBASE
		sd	t1,R_IO_EXT_START_ADDR(t0)

		li	t1,LEDS_SIZE-1	/* Needs to be 1 smaller, se UM for details */
		sd	t1,R_IO_EXT_MULT_SIZE(t0)

		li	t1,LEDS_TIMING0
		sd	t1,R_IO_EXT_TIME_CFG0(t0)

		li	t1,LEDS_TIMING1
		sd	t1,R_IO_EXT_TIME_CFG1(t0)

		li	t1,LEDS_CONFIG
		sd	t1,R_IO_EXT_CFG(t0)


		j	ra

END(board_earlyinit)


/*  *********************************************************************
    *  BOARD_DRAMINFO
    *  
    *  Return the address of the DRAM information table.  Note that
    *  the address must be obtained in a position-independent way,
    *  so avoid the use of the "la" instruction.
    *  
    *  Input parameters: 
    *  	   nothing
    *  	   
    *  Return value:
    *  	   v0 - DRAM info table, return 0 to use default table
    ********************************************************************* */

LEAF(board_draminfo)

		move	v0,zero
		j	ra

END(board_draminfo)



/*  *********************************************************************
    *  BOARD_SETLEDS(x)
    *  
    *  Set LEDs for boot-time progress indication.  Not used if
    *  the board does not have progress LEDs.  This routine
    *  must not call any other routines, since it may be invoked
    *  either from KSEG0 or KSEG1 and it may be invoked 
    *  whether or not the icache is operational.
    *  
    *  Input parameters: 
    *  	   a0 - LED value (8 bits per character, 4 characters)
    *  	   
    *  Return value:
    *  	   nothing
    *  
    *  Registers used:
    *  	   t0,t1,t2,t3
    ********************************************************************* */


#define LED_CHAR0	(32+8*3)
#define LED_CHAR1	(32+8*2)
#define LED_CHAR2	(32+8*1)
#define LED_CHAR3	(32+8*0)

LEAF(board_setleds)

		li	t0,PHYS_TO_K1(LEDS_PHYS)

		rol	a0,a0,8
		and	t1,a0,0xFF
		sb	t1,LED_CHAR0(t0)

		rol	a0,a0,8
		and	t1,a0,0xFF
		sb	t1,LED_CHAR1(t0)

		rol	a0,a0,8
		and	t1,a0,0xFF
		sb	t1,LED_CHAR2(t0)

		rol	a0,a0,8
		and	t1,a0,0xFF
		sb	t1,LED_CHAR3(t0)

		j	ra

END(board_setleds)