arm 驱动进阶：nand flash 驱动程序设计

nand flash 驱动内核实现分析过程：

 

analysis code

s3c2410_nand_inithw
s3c2410_nand_init_chip
nand_scan  // drivers/mtd/nand/nand_base.c 根据nand_chip的底层操作函数识别NAND FLASH，构造mtd_info
    nand_scan_ident
        nand_set_defaults
            if (!chip->select_chip)
                chip->select_chip = nand_select_chip; // 默认值不适用

            if (chip->cmdfunc == NULL)
                chip->cmdfunc = nand_command;
                                    chip->cmd_ctrl(mtd, command, ctrl);
            if (!chip->read_byte)
                chip->read_byte = nand_read_byte;
                                    readb(chip->IO_ADDR_R);
            if (chip->waitfunc == NULL)
                chip->waitfunc = nand_wait;
                                    chip->dev_ready
        
        
        nand_get_flash_type
            chip->select_chip(mtd, 0);
            chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
            *maf_id = chip->read_byte(mtd);
            dev_id = chip->read_byte(mtd);
    nand_scan_tail
            mtd->erase = nand_erase;
            mtd->read = nand_read;
            mtd->write = nand_write;
s3c2410_nand_add_partition
    add_mtd_partitions
        add_mtd_device
            list_for_each(this, &mtd_notifiers) { // 问. mtd_notifiers在哪设置
                                                  // 答. drivers/mtd/mtdchar.c,mtd_blkdev.c调用register_mtd_user
                struct mtd_notifier *not = list_entry(this, struct mtd_notifier, list);
                not->add(mtd);
                // mtd_notify_add  和 blktrans_notify_add
                先看字符设备的mtd_notify_add
                        class_device_create
                        class_device_create
                再看块设备的blktrans_notify_add
                    list_for_each(this, &blktrans_majors) { // 问. blktrans_majors在哪设置
                                                            // 答. drivers\mtd\mdblock.c或mtdblock_ro.c   register_mtd_blktrans
                        struct mtd_blktrans_ops *tr = list_entry(this, struct mtd_blktrans_ops, list);              
                        tr->add_mtd(tr, mtd);
                                mtdblock_add_mtd (drivers\mtd\mdblock.c)
                                    add_mtd_blktrans_dev
                                        alloc_disk
                                        gd->queue = tr->blkcore_priv->rq; // tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
                                        add_disk            

 

 

nand flash 驱动程序设计流程：

 

 

nand flash 驱动程序代码设计：

 

s3c_nand.c

/* 参考 
 * drivers\mtd\nand\s3c2410.c
 * drivers\mtd\nand\at91_nand.c
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/clk.h>
 
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/partitions.h>
 
#include <asm/io.h>
 
#include <asm/arch/regs-nand.h>
#include <asm/arch/nand.h>

struct s3c_nand_regs {
    unsigned long nfconf  ;
    unsigned long nfcont  ;
    unsigned long nfcmd   ;
    unsigned long nfaddr  ;
    unsigned long nfdata  ;
    unsigned long nfeccd0 ;
    unsigned long nfeccd1 ;
    unsigned long nfeccd  ;
    unsigned long nfstat  ;
    unsigned long nfestat0;
    unsigned long nfestat1;
    unsigned long nfmecc0 ;
    unsigned long nfmecc1 ;
    unsigned long nfsecc  ;
    unsigned long nfsblk  ;
    unsigned long nfeblk  ;
};


static struct nand_chip *s3c_nand;
static struct mtd_info *s3c_mtd;
static struct s3c_nand_regs *s3c_nand_regs;

static struct mtd_partition s3c_nand_parts[] = {
    [0] = {
        .name   = "bootloader",
        .size   = 0x00040000,
        .offset    = 0,
    },
    [1] = {
        .name   = "params",
        .offset = MTDPART_OFS_APPEND,
        .size   = 0x00020000,
    },
    [2] = {
        .name   = "kernel",
        .offset = MTDPART_OFS_APPEND,
        .size   = 0x00200000,
    },
    [3] = {
        .name   = "root",
        .offset = MTDPART_OFS_APPEND,
        .size   = MTDPART_SIZ_FULL,
    }
};


static void s3c2440_select_chip(struct mtd_info *mtd, int chipnr)
{
    if (chipnr == -1)
    {
        /* 取消选中: NFCONT[1]设为1 */
        s3c_nand_regs->nfcont |= (1<<1);        
    }
    else
    {
        /* 选中: NFCONT[1]设为0 */
        s3c_nand_regs->nfcont &= ~(1<<1);
    }
}

static void s3c2440_cmd_ctrl(struct mtd_info *mtd, int dat, unsigned int ctrl)
{
    if (ctrl & NAND_CLE)
    {
        /* 发命令: NFCMMD=dat */
        s3c_nand_regs->nfcmd = dat;
    }
    else
    {
        /* 发地址: NFADDR=dat */
        s3c_nand_regs->nfaddr = dat;
    }
}

static int s3c2440_dev_ready(struct mtd_info *mtd)
{
    return (s3c_nand_regs->nfstat & (1<<0));
}


static int s3c_nand_init(void)
{
    struct clk *clk;
    
    /* 1. 分配一个nand_chip结构体 */
    s3c_nand = kzalloc(sizeof(struct nand_chip), GFP_KERNEL);

    s3c_nand_regs = ioremap(0x4E000000, sizeof(struct s3c_nand_regs));
    
    /* 2. 设置nand_chip */
    /* 设置nand_chip是给nand_scan函数使用的, 如果不知道怎么设置, 先看nand_scan怎么使用 
     * 它应该提供:选中,发命令,发地址,发数据,读数据,判断状态的功能
     */
    s3c_nand->select_chip = s3c2440_select_chip;
    s3c_nand->cmd_ctrl    = s3c2440_cmd_ctrl;
    s3c_nand->IO_ADDR_R   = &s3c_nand_regs->nfdata;
    s3c_nand->IO_ADDR_W   = &s3c_nand_regs->nfdata;
    s3c_nand->dev_ready   = s3c2440_dev_ready;
    s3c_nand->ecc.mode    = NAND_ECC_SOFT;
    
    /* 3. 硬件相关的设置: 根据NAND FLASH的手册设置时间参数 */
    /* 使能NAND FLASH控制器的时钟 */
    clk = clk_get(NULL, "nand");
    clk_enable(clk);              /* CLKCON'bit[4] */
    
    /* HCLK=100MHz
     * TACLS:  发出CLE/ALE之后多长时间才发出nWE信号, 从NAND手册可知CLE/ALE与nWE可以同时发出,所以TACLS=0
     * TWRPH0: nWE的脉冲宽度, HCLK x ( TWRPH0 + 1 ), 从NAND手册可知它要>=12ns, 所以TWRPH0>=1
     * TWRPH1: nWE变为高电平后多长时间CLE/ALE才能变为低电平, 从NAND手册可知它要>=5ns, 所以TWRPH1>=0
     */
#define TACLS    0
#define TWRPH0   1
#define TWRPH1   0
    s3c_nand_regs->nfconf = (TACLS<<12) | (TWRPH0<<8) | (TWRPH1<<4);

    /* NFCONT: 
     * BIT1-设为1, 取消片选 
     * BIT0-设为1, 使能NAND FLASH控制器
     */
    s3c_nand_regs->nfcont = (1<<1) | (1<<0);
    
    /* 4. 使用: nand_scan */
    s3c_mtd = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
    s3c_mtd->owner = THIS_MODULE;
    s3c_mtd->priv  = s3c_nand;
    
    nand_scan(s3c_mtd, 1);  /* 识别NAND FLASH, 构造mtd_info */
    
    /* 5. add_mtd_partitions */
    add_mtd_partitions(s3c_mtd, s3c_nand_parts, 4);
    
    //add_mtd_device(s3c_mtd);
    return 0;
}

static void s3c_nand_exit(void)
{
    del_mtd_partitions(s3c_mtd);
    kfree(s3c_mtd);
    iounmap(s3c_nand_regs);
    kfree(s3c_nand);
}

module_init(s3c_nand_init);
module_exit(s3c_nand_exit);

MODULE_LICENSE("GPL");