Nandflash的驱动加载

分析at91sam9260ek的代码示范。

（1）板级初始化。

Board-sam9260ek.c中的初始化调用：

static void __init ek_board_init(void)
{
。。。代码略
/* NAND */
	ek_add_device_nand();
。。。代码略
}

ek_add_device_nand()的代码：

/*
 * NAND flash
 */
static struct mtd_partition __initdata ek_nand_partition[] = {　　　//flash中的分区信息
	{
		.name	= "Partition 1",.offset	= 0,.size	= SZ_256K,},{
		.name	= "Partition 2",.offset	= MTDPART_OFS_NXTBLK,.size	= MTDPART_SIZ_FULL,};

//得到Nandflash分区
static struct mtd_partition * __init nand_partitions(int size,int *num_partitions)
{
	*num_partitions = ARRAY_SIZE(ek_nand_partition);
	return ek_nand_partition;
}

//Nandflash使用的私有数据类型atmel_nand_data
static struct atmel_nand_data __initdata ek_nand_data = {
	.ale		= 21,.cle		= 22,//	.det_pin	= ... not connected
	.rdy_pin	= AT91_PIN_PC13,.enable_pin	= AT91_PIN_PC14,.partition_info	= nand_partitions,//得到Nandflash分区
#if defined(CONFIG_MTD_NAND_ATMEL_BUSWIDTH_16)
	.bus_width_16	= 1,//总线宽度
#else
	.bus_width_16	= 0,#endif
};

//ＳＭＣ配置
static struct sam9_smc_config __initdata ek_nand_smc_config = {
	.ncs_read_setup		= 0,.nrd_setup		= 1,.ncs_write_setup	= 0,.nwe_setup		= 1,.ncs_read_pulse		= 3,.nrd_pulse		= 3,.ncs_write_pulse	= 3,.nwe_pulse		= 3,.read_cycle		= 5,.write_cycle		= 5,.mode			= AT91_SMC_READMODE | AT91_SMC_WRITEMODE | AT91_SMC_EXNWMODE_DISABLE,.tdf_cycles		= 2,};

static void __init ek_add_device_nand(void)
{
	/* setup bus-width (8 or 16) */
	if (ek_nand_data.bus_width_16)
		ek_nand_smc_config.mode |= AT91_SMC_DBW_16;
	else
		ek_nand_smc_config.mode |= AT91_SMC_DBW_8;

	/* configure chip-select 3 (NAND) */
	sam9_smc_configure(3,&ek_nand_smc_config);

	at91_add_device_nand(&ek_nand_data); //跳到At91sam9260_devices.c中执行
}

At91sam9260_devices.c中的代码：

static struct atmel_nand_data nand_data;

#define NAND_BASE	AT91_CHIPSELECT_3

static struct resource nand_resources[] = {
	[0] = {
		.start	= NAND_BASE,.end	= NAND_BASE + SZ_256M - 1,.flags	= IORESOURCE_MEM,[1] = {
		.start	= AT91_BASE_SYS + AT91_ECC,.end	= AT91_BASE_SYS + AT91_ECC + SZ_512 - 1,}
};

static struct platform_device at91sam9260_nand_device = {
	.name		= "atmel_nand",.id		= -1,.dev		= {
				.platform_data	= &nand_data,.resource	= nand_resources,.num_resources	= ARRAY_SIZE(nand_resources),};

void __init at91_add_device_nand(struct atmel_nand_data *data)
{
	unsigned long csa;

	if (!data)
		return;

	csa = at91_sys_read(AT91_MATRIX_EBICSA);
	at91_sys_write(AT91_MATRIX_EBICSA,　　　　　　　　　　　　　　　csa | AT91_MATRIX_CS3A_SMC_SMARTMEDIA);

	/* enable pin */
	if (data->enable_pin)
		at91_set_gpio_output(data->enable_pin,1); 
	/* ready/busy pin */
	if (data->rdy_pin)
		at91_set_gpio_input(data->rdy_pin,1);　 

	/* card detect pin */
	if (data->det_pin)
		at91_set_gpio_input(data->det_pin,1);

	nand_data = *data;
	platform_device_register(&at91sam9260_nand_device);
}

(2)驱动初始化

//驱动私有数据结构
struct atmel_nand_host {
	struct nand_chip	nand_chip;  //Nandflash与mtd的接口
	struct mtd_info		mtd;　　//主分区的mtd_info，创建分区使用
	void __iomem		*io_base;    //虚拟地址
	struct atmel_nand_data	*board;  //板级私有数据
	struct device		*dev;        
	void __iomem		*ecc;　　　　//ecc的虚拟地址
};

static int __init atmel_nand_probe(struct platform_device *pdev)
{
	struct atmel_nand_host *host;
	struct mtd_info *mtd;
	struct nand_chip *nand_chip;
	struct resource *regs;
	struct resource *mem;
   . . .
   //为驱动私有数据分配空间并清０
   host = kzalloc(sizeof(struct atmel_nand_host),GFP_KERNEL);
　 . . . 
	mtd = &host->mtd;
	nand_chip = &host->nand_chip;
	host->board = pdev->dev.platform_data;  //板级私有数据
	host->dev = &pdev->dev;    //dev

	nand_chip->priv = host;		/* link the private data structures */
	mtd->priv = nand_chip;     //链接nand_chip到mtd
	mtd->owner = THIS_MODULE;

	/* Set address of NAND IO lines */
	nand_chip->IO_ADDR_R = host->io_base;　　　//读地址
	nand_chip->IO_ADDR_W = host->io_base;     //写地址
	nand_chip->cmd_ctrl = atmel_nand_cmd_ctrl;   
//上面这个是写命令或写地址接口

	if (host->board->rdy_pin)
		nand_chip->dev_ready = atmel_nand_device_ready;

//ECC的初始化代码，略

//从数据手册获取命令延迟时间
nand_chip->chip_delay = 20;		/* 20us command delay time */

if (host->board->bus_width_16) {	/* 16-bit bus width */
		nand_chip->options |= NAND_BUSWIDTH_16;
		nand_chip->read_buf = atmel_read_buf16;
		nand_chip->write_buf = atmel_write_buf16;
	} else {
		nand_chip->read_buf = atmel_read_buf;
		nand_chip->write_buf = atmel_write_buf;
	}

	platform_set_drvdata(pdev,host);  //设置数据到pdev
	atmel_nand_enable(host);

. . .
	/* first scan to find the device and get the page size */
	if (nand_scan_ident(mtd,1)) {
		res = -ENXIO;
		goto err_scan_ident;
	}

    //根据扫描得到的flash页大小初始化ＥＣＣ硬件，代码略

	/* second phase scan */
	if (nand_scan_tail(mtd)) {
		res = -ENXIO;
		goto err_scan_tail;
	}


#ifdef CONFIG_MTD_PARTITIONS
#ifdef CONFIG_MTD_CMDLINE_PARTS
	mtd->name = "atmel_nand";
	num_partitions = parse_mtd_partitions(mtd,part_probes,//提取flash中的分区信息

					      &partitions,0);
#endif
    //如果提取flash中的分区信息不存在，则读取板级初始化设定的分区信息
	if (num_partitions <= 0 && host->board->partition_info)
		partitions = host->board->partition_info(mtd->size,&num_partitions);

	res = add_mtd_partitions(mtd,partitions,num_partitions);
#else
	res = add_mtd_device(mtd);　//只有一个主分区的情况，不支持分区表
#endif

	if (!res)
		return res;
　　. . .略
}

?

nand_chip->cmd_ctrl是写命令或写地址接口，它可以是下面三个值：

#define NAND_CTRL_CLE		(NAND_NCE | NAND_CLE)
#define NAND_CTRL_ALE		(NAND_NCE | NAND_ALE)
#define NAND_CTRL_CHANGE	     0x80

?

(3)?ECC的配置

ECC的状态：

/*
 * Constants for ECC_MODES
 */
typedef enum {
	NAND_ECC_NONE,NAND_ECC_SOFT,NAND_ECC_HW,NAND_ECC_HW_SYNDROME,} nand_ecc_modes_t;

如果是软件ＥＣＣ：

nand_chip->ecc.mode = NAND_ECC_SOFT;
			nand_chip->ecc.mode = NAND_ECC_SOFT;
			nand_chip->ecc.calculate = NULL;
			nand_chip->ecc.correct = NULL;
			nand_chip->ecc.hwctl = NULL;
			nand_chip->ecc.read_page = NULL;
			nand_chip->ecc.postpad = 0;
			nand_chip->ecc.prepad = 0;
			nand_chip->ecc.bytes = 0;

?

如果是硬件ＥＣＣ：

		nand_chip->ecc.mode = NAND_ECC_HW;
		nand_chip->ecc.calculate = atmel_nand_calculate;　 //计算ＥＣＣ
		nand_chip->ecc.correct = atmel_nand_correct;      //读完一页数据后判断ＥＣＣ是否正确
		nand_chip->ecc.hwctl = atmel_nand_hwctl;        //硬件控制函数，大部分ＣＰＵ不用支持
		nand_chip->ecc.read_page = atmel_nand_read_page;　//有硬件ＥＣＣ的情况下读一个页数据的接口
		nand_chip->ecc.bytes = 4;


nand_chip->ecc.layout是一个结构：


struct nand_oobfree {
	__u32 offset;
	__u32 length;
};

#define MTD_MAX_OOBFREE_ENTRIES	8
/*
 * ECC layout control structure. Exported to userspace for
 * diagnosis and to allow creation of raw images
 */
struct nand_ecclayout {
	__u32 eccbytes;　　　//ECC的大小（字节）
	__u32 eccpos[64];　　//ECC所在的字节位置
	__u32 oobavail;　　　
	struct nand_oobfree oobfree[MTD_MAX_OOBFREE_ENTRIES];　 //ＯＯＢ可用的数据空间
};

例子：
/* oob layout for large page size
 * bad block info is on bytes 0 and 1
 * the bytes have to be consecutives to avoid
 * several NAND_CMD_RNDOUT during read
 */
static struct nand_ecclayout atmel_oobinfo_large = {
	.eccbytes	= 4,.eccpos		= {60,61,62,63},.oobfree	= {
		{2,58}
	},};

/* oob layout for small page size
 * bad block info is on bytes 4 and 5
 * the bytes have to be consecutives to avoid
 * several NAND_CMD_RNDOUT during read
 */
static struct nand_ecclayout atmel_oobinfo_small = {
	.eccbytes	= 4,.eccpos		= {0,1,2,3},.oobfree	= {
		{6,10}
	},};

?

总结： NAND Flash的加载过程中，定义了一个结构atmel_nand_host，它的成员包含了nand_chip和mtd_info结构。nand_chip->priv指向atmel_nand_host结构，mtd_info->priv指向nand_chip结构。Nand_base.c中的nand_scan_ident函数完成NAND Flash探测的大部分工作。