ARM+LINUX移植攻略（九）U-boot-2009.08移植TE2440II开发板--支持Nandflash启动
哈尔滨理工大学软件工程专业08-7李万鹏原创作品，转载请标明出处
http://blog.csdn.net/woshixingaaa/archive/2011/02/17/6192146.aspx
从nandflash启动最关键的部分是rellocated，即代码重定位。s3c2440数据手册有这么一段，所以代码重定位是由nandflash控制器自动完成的，而不是一些人说的由CPU完成的。
在include/configs/TE2440II.h中添加nandflash控制器的定义：
/*
* NAND flash setting
*/
#if defined(CONFIG_CMD_NAND)
#define CONFIG_SYS_NAND_BASE 0x4e000000
#define CONFIG_SYS_MAX_NAND_DEVICE 1
#define CONFIG_MTD_NAND_VERIFY_WRITE 1
#define NAND_SAMSUNG_LP_OPTIONS 1 //大页要添加这个
#define CONFIG_NAND_S3C2440 1
#define CONFIG_S3C2440_NAND_BOOT 1
#define NAND_CTL_BASE 0x4E000000
#define oNFCONF 0x00
#define oNFCONT 0x04
#define oNFADDR 0x0c
#define oNFDATA 0x10
#define oNFCMD 0x08
#define oNFSTAT 0x20
#define oNFECC 0x2c
#endif
在
/*
* Command line configuration.
*/
下添加
#define CONFIG_CMD_NAND
修改环境变量那部分
//#undef CONFIG_ENV_IS_IN_FLASH 1
#define CONFIG_ENV_IS_IN_NAND 1
其次，修改cpu/arm920t/start.S这个文件，使u-boot从Nand Flash启动
为了让他自动识别是从norflash还是从nandflash启动添加，BWSCON的第2，1为即OM1，OM0。为00时是从nandflash启动，其他为从norflash启动，判断OM1和OM0，就可以让uboot自动识别启动方式。
#define BWSCON 0x48000000
ldr r0, =BWSCON
ldr r1,[r0]
ands r1, r1, #0x6
beq nand_boot
nor_boot:
#ifndef CONFIG_SKIP_RELOCATE_UBOOT
添加nandflash的启动代码，核心是relocated部分。首先设置nandflash控制器，然后将nandflash中从0开始的uboot复制到SDRAM中的TEXT_BASE处，TEXT_BASE在config.mk中定义，值为0x33f80000。复制好后，比较nandflash和SDRAM中的数据，如果前4K相同，表示搬移成功。下面的汇编代码注意ATPC标准规定r0~r3，用于参数传递和返回值。
/********************************************************/
//#define CONFIG_S3C2440_NAND_BOOT 1
nand_boot:
#define CONFIG_S3C2440_NAND_BOOT 1
#define NAND_CTL_BASE 0x4E000000
/* Offset */
#define oNFCONF 0x00
#define oNFCONT 0x04
#define oNFCMD 0x08
#define oNFSTAT 0x20
#define LENGTH_UBOOT 0x40000
@ reset NAND
mov r1, #NAND_CTL_BASE
ldr r2, =( (7<<12)|(7<<8)|(7<<4)|(0<<0) )
str r2, [r1, #oNFCONF]
ldr r2, [r1, #oNFCONF]
ldr r2, =((1<<4)|(0<<1)|(1<<0) ) @ Active low CE Control
str r2, [r1, #oNFCONT]
ldr r2, [r1, #oNFCONT]
ldr r2, =(0x6) @ RnB Clear
str r2, [r1, #oNFSTAT]
ldr r2, [r1, #oNFSTAT]
mov r2, #0xff @ RESET command
strb r2, [r1, #oNFCMD]
mov r3, #0 @ wait
nand1:
add r3, r3, #0x1
cmp r3, #0xa
blt nand1
nand2:
ldr r2, [r1, #oNFSTAT] @ wait ready
tst r2, #0x4
beq nand2
ldr r2, [r1, #oNFCONT]
orr r2, r2, #0x2 @ Flash Memory Chip Disable
str r2, [r1, #oNFCONT]
@ get read to call C functions (for nand_read())
ldr sp, DW_STACK_START @ setup stack pointer
mov fp, #0 @ no previous frame, so fp=0
@ copy U-Boot to RAM
ldr r0, =TEXT_BASE //传递给C代码的第一个参数：u-boot在RAM中的起始地址
mov r1, #0x0 //传递给C代码的第二个参数：Nand Flash的起始地址
mov r2, #LENGTH_UBOOT //传递给C代码的第三个参数：u-boot的长度大小
/**********************************************************/
/************************************************************/
bl nand_read_ll
tst r0, #0x0
beq ok_nand_read
bad_nand_read:
loop2:
b loop2 @ infinite loop
ok_nand_read:
@ verify
mov r0, #0
ldr r1, =TEXT_BASE
mov r2, #0x400 @ 4 bytes * 1024 = 4K-bytes
go_next:
ldr r3, [r0], #4
ldr r4, [r1], #4
teq r3, r4
bne notmatch
subs r2, r2, #4
beq stack_setup
bne go_next
notmatch:
loop3:
b loop3 @ infinite loop
#endif
/* Set up the stack */
stack_setup:
ldr r0, _TEXT_BASE /* upper 128 KiB: relocated uboot */
sub r0, r0, #CONFIG_SYS_MALLOC_LEN /* malloc area */
sub r0, r0, #CONFIG_SYS_GBL_DATA_SIZE /* bdinfo */
#ifdef CONFIG_USE_IRQ
sub r0, r0, #(CONFIG_STACKSIZE_IRQ+CONFIG_STACKSIZE_FIQ)
#endif
sub sp, r0, #12 /* leave 3 words for abort-stack */
clear_bss:
ldr r0, _bss_start /* find start of bss segment */
ldr r1, _bss_end /* stop here */
mov r2, #0x00000000 /* clear */
clbss_l:str r2, [r0] /* clear loop... */
add r0, r0, #4
cmp r0, r1
ble clbss_l
ldr pc, _start_armboot
_start_armboot: .word start_armboot
#define STACK_BASE 0x33ff8000
#define STACK_SIZE 0x10000
.align 2
DW_STACK_START: .word STACK_BASE+STACK_SIZE-4
在board/samsung/TE2440II/目录下添加nand_read.c文件，内容如下，在K9F2G08的datasheet中有这么一段
所以地址由5个周期传完。前两个周期用来寻页内地址。后三个周期是页间寻址。1device=2048block=2048*64page=2048*64*(2k+64)Bytes
#include <config.h>
#include <linux/mtd/nand.h>
#define __REGb(x) (*(volatile unsigned char *)(x))
#define __REGw(x) (*(volatile unsigned short *)(x))
#define __REGi(x) (*(volatile unsigned int *)(x))
#define NF_BASE 0x4e000000
#define NFCONF __REGi(NF_BASE + 0x0)
#define NFCONT __REGi(NF_BASE + 0x4)
#define NFCMD __REGb(NF_BASE + 0x8)
#define NFADDR __REGb(NF_BASE + 0xc)
#define NFDATA __REGb(NF_BASE + 0x10)
#define NFDATA16 __REGw(NF_BASE + 0x10)
#define NFSTAT __REGb(NF_BASE + 0x20)
#define NFSTAT_BUSY (1 << 2)
#define nand_select() (NFCONT &= ~(1 << 1))
#define nand_deselect() (NFCONT |= (1 << 1))
#define nand_clear_RnB() (NFSTAT |= NFSTAT_BUSY)
static inline void nand_wait(void)
{
int i;
while (!(NFSTAT & NFSTAT_BUSY))
for (i=0; i<10; i++);
}
/* configuration for 2440 with 2048byte sized flash */
#define NAND_5_ADDR_CYCLE
#define NAND_PAGE_SIZE 2048
#define BAD_BLOCK_OFFSET NAND_PAGE_SIZE
#define NAND_BLOCK_MASK (NAND_PAGE_SIZE - 1)
#define NAND_BLOCK_SIZE (NAND_PAGE_SIZE * 64)
static int nand_read_page_ll(unsigned char *buf, unsigned long addr)
{
unsigned int i, page_num;
nand_clear_RnB();
NFCMD = NAND_CMD_READ0;
page_num = addr >> 11; /* addr / 2048 */
/* Write Address */
NFADDR = 0;
NFADDR = 0;
NFADDR = page_num & 0xff;
NFADDR = (page_num >> 8) & 0xff;
NFADDR = (page_num >> 16) & 0xff;
NFCMD = NAND_CMD_READSTART;
nand_wait();