TX2440 ARM开发板Uboot移植（三、添加Nand Flash的有关操作支持

发布时间：2020-12-15 17:40:05 所属栏目：百科来源：网络整理

导读：在上一节中我们说过，通常在嵌入式bootloader中，有两种方式来引导启动内核：从Nor Flash启动和从Nand Flash启动，但不管是从Nor启动或者从Nand启动，进入第二阶段以后，两者的执行流程是相同的。当u-boot的start.S运行到“_start_armboot:?.word start_armb

在上一节中我们说过，通常在嵌入式bootloader中，有两种方式来引导启动内核：从Nor Flash启动和从Nand Flash启动，但不管是从Nor启动或者从Nand启动，进入第二阶段以后，两者的执行流程是相同的。当u-boot的start.S运行到“_start_armboot:?.word start_armboot”时，就会调用lib_arm/board.c中的start_armboot函数，至此u-boot正式进入第二阶段。此时注意：以前较早的u-boot版本进入第二阶段后，对Nand Flash的支持有新旧两套代码，新代码在drivers/nand目录下，旧代码在drivers/nand_legacy目录下，CFG_NAND_LEGACY宏决定了使用哪套代码，如果定义了该宏就使用旧代码，否则使用新代码。但是现在的u-boot版本对Nand的初始化、读写实现是基于最近的Linux内核的MTD架构，删除了以前传统的执行方法，使移植没有以前那样复杂了，实现Nand的操作和基本命令都直接在drivers/mtd/nand目录下(在doc/README.nand中讲得很清楚)。下面我们结合代码来分析一下u-boot在第二阶段的执行流程：

1.lib_arm/board.c文件中的start_armboot函数调用了drivers/mtd/nand/nand.c文件中的nand_init函数，如下：
??#if defined(CONFIG_CMD_NAND)??????//可以看到CONFIG_CMD_NAND宏决定了Nand的初始化
??????puts ("NAND: ");
????? nand_init();
? #endif
2.nand_init调用了同文件下的nand_init_chip函数；
3.nand_init_chip函数调用cpu/arm920t/s3c24x0/nand.c文件下的board_nand_init函数，然后再调用drivers/mtd/nand/nand_base.c函数中的nand_scan函数；
4.nand_scan函数调用了同文件下的nand_scan_ident函数等。

因为2440和2410对nand控制器的操作有很大的不同，所以s3c24x0/nand.c下对nandflash操作的函数就是我们做移植需要实现的部分了，他与具体的Nand Flash硬件密切相关。

1、修改 cpuarm920ts3c24x0nand.c 文件内容为：

#include <common.h>
#if defined(CONFIG_CMD_NAND) && !defined(CFG_NAND_LEGACY)
#include <nand.h>
#if defined(CONFIG_S3C2410)
#include <s3c2410.h>
#define S3C2410_NFSTAT_READY??? (1<<0)
#define S3C2410_NFCONF_nFCE???? (1<<11)
/* select chip,for s3c2410 */
static void s3c2410_nand_select_chip(struct mtd_info *mtd,int chip)
{
??? S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
??? if (chip == -1) {
??????? s3c2410nand->NFCONF |= S3C2410_NFCONF_nFCE;
??? } else {
??????? s3c2410nand->NFCONF &= ~S3C2410_NFCONF_nFCE;
??? }
}

static void s3c2410_nand_hwcontrol(struct mtd_info *mtd,int cmd)
{
??? S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
??? struct nand_chip *chip = mtd->priv;

??? switch (cmd) {
??? case NAND_CTL_SETNCE:
????s3c2410nand->NFCONF &= ~S3C2410_NFCONF_nFCE;
??? case NAND_CTL_CLRNCE:
????s3c2410nand->NFCONF |= S3C2410_NFCONF_nFCE;
??????? printf("%s: called for NCEn",__FUNCTION__);
??????? break;
??? case NAND_CTL_SETCLE:
??????? chip->IO_ADDR_W = (void *)&s3c2410nand->NFCMD;
??????? break;
??? case NAND_CTL_SETALE:
??????? chip->IO_ADDR_W = (void *)&s3c2410nand->NFADDR;
??????? break;
??????? /* NAND_CTL_CLRCLE: */
??????? /* NAND_CTL_CLRALE: */
??? default:
??????? chip->IO_ADDR_W = (void *)&s3c2410nand->NFDATA;
??????? break;
??? }
}

/* s3c2410_nand_devready()
?*
?* returns 0 if the nand is busy,1 if it is ready
?*/
static int s3c2410_nand_devready(struct mtd_info *mtd)
{
??? S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
??? return (s3c2410nand->NFSTAT & S3C2410_NFSTAT_READY);
}
#elif defined(CONFIG_S3C2440)
#include <s3c2440.h>
#define S3C2440_NFSTAT_READY??? (1<<0)
#define S3C2440_NFCONT_nFCE???? (1<<1)
/* select chip,for s3c2440 */
static void s3c2440_nand_select_chip(struct mtd_info *mtd,int chip)
{
??? S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
??? if (chip == -1) {
??????? s3c2440nand->NFCONT |= S3C2440_NFCONT_nFCE;
??? } else {
??????? s3c2440nand->NFCONT &= ~S3C2440_NFCONT_nFCE;
??? }
}

/* command and control functions */
static void s3c2440_nand_hwcontrol(struct mtd_info *mtd,int cmd)
{
??? S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
??? struct nand_chip *chip = mtd->priv;

??? switch (cmd) {
??? case NAND_CTL_SETNCE:
????s3c2440nand->NFCONT &= ~S3C2440_NFCONT_nFCE;
??? case NAND_CTL_CLRNCE:
????s3c2440nand->NFCONT |= S3C2440_NFCONT_nFCE;
??????? printf("%s: called for NCEn",__FUNCTION__);
??????? break;
??? case NAND_CTL_SETCLE:
??????? chip->IO_ADDR_W = (void *)&s3c2440nand->NFCMD;
??????? break;
??? case NAND_CTL_SETALE:
??????? chip->IO_ADDR_W = (void *)&s3c2440nand->NFADDR;
??????? break;
??????? /* NAND_CTL_CLRCLE: */
??????? /* NAND_CTL_CLRALE: */
??? default:
??????? chip->IO_ADDR_W = (void *)&s3c2440nand->NFDATA;
??????? break;
??? }
}

/* s3c2440_nand_devready()
?*
?* returns 0 if the nand is busy,1 if it is ready
?*/
static int s3c2440_nand_devready(struct mtd_info *mtd)
{
??? S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
??? return (s3c2440nand->NFSTAT & S3C2440_NFSTAT_READY);
}
#endif
/*
?* Called by drivers/nand/nand.c,initialize the interface of nand flash
?*/
int board_nand_init(struct nand_chip *chip)
{
#define TACLS?? 0
#define TWRPH0? 4
#define TWRPH1? 2
#if defined(CONFIG_S3C2410)
??? S3C2410_NAND * const s3c2410nand = S3C2410_GetBase_NAND();
??/* Enable NAND flash controller,Initialize ECC,enable chip select,Set flash memory timing */
??s3c2410nand->NFCONF = (1<<15)|(1<<12)|(1<<11)|(TACLS<<8)|(TWRPH0<<4)|(TWRPH1<<0);?
??? chip->IO_ADDR_R??? = (void *)&s3c2410nand->NFDATA;
??? chip->IO_ADDR_W??? = (void *)&s3c2410nand->NFDATA;
??? chip->hwcontrol??? = s3c2410_nand_hwcontrol;
??? chip->dev_ready??? = s3c2410_nand_devready;
??? chip->select_chip? = s3c2410_nand_select_chip;
#elif defined(CONFIG_S3C2440)
??? S3C2440_NAND * const s3c2440nand = S3C2440_GetBase_NAND();
??? s3c2440nand->NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
??? /* Initialize ECC,NAND flash controller enable */
??? s3c2440nand->NFCONT = (1<<4)|(0<<1)|(1<<0);
??? chip->IO_ADDR_R??? = (void *)&s3c2440nand->NFDATA;
??? chip->IO_ADDR_W??? = (void *)&s3c2440nand->NFDATA;
??? chip->hwcontrol??? = s3c2440_nand_hwcontrol;
??? chip->dev_ready??? = s3c2440_nand_devready;
??? chip->select_chip? = s3c2440_nand_select_chip;
#endif
??? chip->options????? = 0;
??? chip->eccmode?????? = NAND_ECC_SOFT;
? return 0;
}
#endif

2、修改文件 include/s3c2440.h ，将 S3C2410_GetBase_NAND 修改为? S3C2440_GetBase_NAND ；仿照S3C2410_GetBase_NAND函数（96行）定义2440的函数：

static inline S3C2440_NAND * const S3C2440_GetBase_NAND(void)
{
??? return (S3C2440_NAND * const)S3C2440_NAND_BASE;
} 重新编译u-boot并下载到Nand Flash中，把开发板调到Nand档从Nand启动。现在u-boot已经对我们开发板上256M的Nand Flash完全支持了。Nand相关的基本命令也都可以正常使用了。

3、将环境变量存储到Nand Flash中

从上面的启动信息看，有一个警告信息“*** Warning - bad CRC or NAND,using default environment”，这是因为没有将u-boot的环境变量保存nand中的缘故。u-boot在默认的情况下把环境变量都是保存到Nor Flash中的，所以要修改代码，让他保存到Nand中。修改 include/configs/smdk2440.h 文件：

/*?配置环境变量存放设置?*/
#define CFG_ENV_ADDR? (CFG_FLASH_BASE + 0x100000) /* 使用NorFlash时，环境变量存放的开始地址 */
//#define? CFG_ENV_IS_IN_FLASH 1?????? ?????????????/* 环境变量保存的位置在NorFlash? */
#define CFG_ENV_IS_IN_NAND 1??????????????????????? /*? 环境变量保存的位置在NandFlash? */
#define CFG_ENV_OFFSET 0x60000?????????????????? /* 使用NandFlash时，环境变量存放的偏移地址 */
#define CFG_ENV_SIZE? 0x20000?????????????? /*Total Size of Environment Sector；一般设定为NandFlash的一个Sector的大小*/

4、最后编译u-boot，生成u-boot.bin文件。将u-boot.bin下载到开发板的Nand Flash中，再把开发板调到Nand启动档，保存环境变量后重启开发板，那条警告信息现在没有了。

（编辑：李大同）

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