U-Boot 분석(4)

memsetup.S

이전 start.S소스 중에서 cpu_init_crit()에서 memsetup으로 제어가 넘어왔다.

memsetup을 살펴보도록 하겠다.

/*
 *      A     EEEE  SSSS   OOO  PPPP
 *     A A    E     S     O   O P   P
 *    AAAAA   EEEE  SSSS  O   O PPPP
 *   A     A  E         S O   O P
 *   A     A  EEEE  SSSS   OOO  P
 *
 *  An Entertainment Solution On a Platform (AESOP) is a completely Open Source
 *  based graphical user environment and suite of applications for PDAs and other
 *  devices running Linux. It is included in various embedded Linux distributions
 *  such as OpenZaurus - http://www.aesop-embedded.org
 *
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *
 * Title           : memsetup.S
 * Author          :
 * Created date    : 2005. 06. 26. 23:05:30 KST
 * Description     :
 *
 * $Revision: 1.1.1.1 $
 * $Log: memsetup.S,v $
 * Revision 1.1.1.1  2005/06/27 17:04:30  linuxpark
 * Initial import.
 * 
 * 
 *
 */
#ident  "@(*) $Header: /cvsroot/aesop-embedded/u-boot-aesop/board/aesop2440/memsetup.S,v 1.1.1.1 2005/06/27 17:04:30 linuxpark Exp $"

 

/*
 * Memory Setup stuff - taken from blob memsetup.S
 *
 * Copyright (C) 1999 2000 2001 Erik Mouw (J.A.K.Mouw@its.tudelft.nl) and
 *                     Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
 *
 * Modified for the Samsung SMDK2410 by
 * (C) Copyright 2002
 * David Mueller, ELSOFT AG, <d.mueller@elsoft.ch>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <config.h>
#include <version.h>

/* some parameters for the board */

/*
 *
 * Taken from linux/arch/arm/boot/compressed/head-s3c2410.S
 *
 * Copyright (C) 2002 Samsung Electronics SW.LEE  <hitchcar@sec.samsung.com>
 *
 */

#define BWSCON 0x48000000

/* BWSCON */
#define DW8    (0x0)
#define DW16    (0x1)
#define DW32    (0x2)
#define WAIT    (0x1<<2)
#define UBLB    (0x1<<3)

#define B1_BWSCON    (DW32)
#define B2_BWSCON    (DW16)
#define B3_BWSCON    (DW16 + WAIT + UBLB)
#define B4_BWSCON    (DW16)
#define B5_BWSCON    (DW16)
#define B6_BWSCON    (DW32)
#define B7_BWSCON    (DW32)

/* BANK0CON */
#define B0_Tacs    0x0 /*  0clk */
#define B0_Tcos    0x0 /*  0clk */
#define B0_Tacc    0x7 /* 14clk */
#define B0_Tcoh    0x0 /*  0clk */
#define B0_Tah    0x0 /*  0clk */
#define B0_Tacp    0x0
#define B0_PMC    0x0 /* normal */

/* BANK1CON */
#define B1_Tacs    0x0 /*  0clk */
#define B1_Tcos    0x0 /*  0clk */
#define B1_Tacc    0x7 /* 14clk */
#define B1_Tcoh    0x0 /*  0clk */
#define B1_Tah    0x0 /*  0clk */
#define B1_Tacp    0x0
#define B1_PMC    0x0

#define B2_Tacs    0x0
#define B2_Tcos    0x0
#define B2_Tacc    0x7
#define B2_Tcoh    0x0
#define B2_Tah    0x0
#define B2_Tacp    0x0
#define B2_PMC    0x0

#define B3_Tacs    0x0 /*  0clk */
#define B3_Tcos    0x3 /*  4clk */
#define B3_Tacc    0x7 /* 14clk */
#define B3_Tcoh    0x1 /*  1clk */
#define B3_Tah    0x0 /*  0clk */
#define B3_Tacp    0x3     /*  6clk */
#define B3_PMC    0x0 /* normal */

#define B4_Tacs    0x0 /*  0clk */
#define B4_Tcos    0x0 /*  0clk */
#define B4_Tacc    0x7 /* 14clk */
#define B4_Tcoh    0x0 /*  0clk */
#define B4_Tah    0x0 /*  0clk */
#define B4_Tacp    0x0
#define B4_PMC    0x0 /* normal */

#define B5_Tacs    0x0 /*  0clk */
#define B5_Tcos    0x0 /*  0clk */
#define B5_Tacc    0x7 /* 14clk */
#define B5_Tcoh    0x0 /*  0clk */
#define B5_Tah    0x0 /*  0clk */
#define B5_Tacp    0x0
#define B5_PMC    0x0 /* normal */

#define B6_MT    0x3 /* SDRAM */
#define B6_Trcd     0x1
#define B6_SCAN    0x1 /* 9bit */

#define B7_MT    0x3 /* SDRAM */
#define B7_Trcd    0x1 /* 3clk */
#define B7_SCAN    0x1 /* 9bit */

/* REFRESH parameter */
#define REFEN    0x1 /* Refresh enable */
#define TREFMD    0x0 /* CBR(CAS before RAS)/Auto refresh */
#define Trp    0x0 /* 2clk */
#define Trc    0x3 /* 7clk */
#define Tchr    0x2 /* 3clk */
#define REFCNT    1113 /* period=15.6us, HCLK=60Mhz, (2048+1-15.6*60) */
/**************************************/

_TEXT_BASE:
 .word TEXT_BASE

 

/* S3C2440의 데이터시트를 보면서 코드를 따라 차근차근 그려가며 분석해보면 재미있게 이해할 수 있다. */
//////////////////////////////////////////////////////////////////////////////////////////////
.globl memsetup   // Linker에게 symbol처리 할 수 있도록 export        
memsetup:    // SMRDATA는 아직 메모리가 초기화 되지 않았으므로        
      // flash에서 읽기 위하여 r0에 상대적인 위치를 저장한다.      
 ldr     r0, =SMRDATA // SMRDATA address를 r0레지스터로 이동.
 ldr r1, _TEXT_BASE // _TEXT_BASE에 잇는 data를 r1레지스터로 이동.
 sub r0, r0, r1   // r0에 상대주소값을 저장한다. r0 := r0 - r1
 ldr r1, =BWSCON  /* Bus Width Status Controller의 주소를 r1에 저장 */
 add     r2, r0, #13*4 // 13개의 word레지스터를 r0레지스터와 더한 후 r2레지스터로 이동.
      // 13번 loop를 돌리기 위해 compare할 레지스터 setting(즉, end Address)
0:      // 이곳으로 분기해 염.............................................................................
 ldr     r3, [r0], #4  // r0가 가리키는 address의 data를 r3레지스터로 이동 후 r0값을 4증가시킨다.
 str     r3, [r1], #4  // r1이 가리키는 address에 r3 data를 저장 후 r1값을 4증가시킨다.
 cmp     r2, r0   // r2, r0값을 비교하여 그 결과 값을 CPSR에 setting
 bne     0b    // Z flag가 clear(0)이면 분기해라............................................................
      // set(1)이면 다음 명령어 수행.
                       
 /* everything is fine now */                 
 mov pc, lr   // memsetup함수를 호출한 start.S의 cpu_init_crit으로 복귀한다.      
//////////////////////////////////////////////////////////////////////////////////////////////
 .ltorg
/* the literal pools origin */

SMRDATA:
    .word (0+(B1_BWSCON<<4)+(B2_BWSCON<<8)+(B3_BWSCON<<12)+(B4_BWSCON<<16)+(B5_BWSCON<<20)+(B6_BWSCON<<24)+(B7_BWSCON<<28))
    .word ((B0_Tacs<<13)+(B0_Tcos<<11)+(B0_Tacc<<8)+(B0_Tcoh<<6)+(B0_Tah<<4)+(B0_Tacp<<2)+(B0_PMC))
    .word ((B1_Tacs<<13)+(B1_Tcos<<11)+(B1_Tacc<<8)+(B1_Tcoh<<6)+(B1_Tah<<4)+(B1_Tacp<<2)+(B1_PMC))
    .word ((B2_Tacs<<13)+(B2_Tcos<<11)+(B2_Tacc<<8)+(B2_Tcoh<<6)+(B2_Tah<<4)+(B2_Tacp<<2)+(B2_PMC))
    .word ((B3_Tacs<<13)+(B3_Tcos<<11)+(B3_Tacc<<8)+(B3_Tcoh<<6)+(B3_Tah<<4)+(B3_Tacp<<2)+(B3_PMC))
    .word ((B4_Tacs<<13)+(B4_Tcos<<11)+(B4_Tacc<<8)+(B4_Tcoh<<6)+(B4_Tah<<4)+(B4_Tacp<<2)+(B4_PMC))
    .word ((B5_Tacs<<13)+(B5_Tcos<<11)+(B5_Tacc<<8)+(B5_Tcoh<<6)+(B5_Tah<<4)+(B5_Tacp<<2)+(B5_PMC))
    .word ((B6_MT<<15)+(B6_Trcd<<2)+(B6_SCAN))
    .word ((B7_MT<<15)+(B7_Trcd<<2)+(B7_SCAN))
    .word ((REFEN<<23)+(TREFMD<<22)+(Trp<<20)+(Trc<<18)+(Tchr<<16)+REFCNT)
    .word 0x32
    .word 0x30
    .word 0x30

---------------

출처 : http://blog.naver.com/idrukawa/100054113511