驱动09.nand flash


1 nand flash的操作

目的:读地址A的数据,把数据B写到地址A。

问1. 原理图上NAND FLASH和S3C2440之间只有数据线,怎么传输地址?
答1.在DATA0~DATA7上既传输数据,又传输地址,当ALE为高电平时传输的是地址。

问2. 从NAND FLASH芯片手册可知,要操作NAND FLASH需要先发出命令
     怎么传入命令?
答2.在DATA0~DATA7上既传输数据,又传输地址,也传输命令
     当ALE为高电平时传输的是地址,
     当CLE为高电平时传输的是命令
     当ALE和CLE都为低电平时传输的是数据
问3. 数据线既接到NAND FLASH,也接到NOR FLASH,还接到SDRAM、DM9000等等,那么怎么避免干扰?
答3. 这些设备,要访问之必须"选中",没有选中的芯片不会工作,相当于没接一样。(内存控制器
问4. 假设烧写NAND FLASH,把命令、地址、数据发给它之后,
     NAND FLASH肯定不可能瞬间完成烧写的,怎么判断烧写完成?
答4. 通过状态引脚RnB来判断:它为高电平表示就绪,它为低电平表示正忙

问5. 怎么操作NAND FLASH呢?
答5. 根据NAND FLASH的芯片手册,一般的过程是:
     发出命令
     发出地址
     发出数据/读数据

2 分析nand flash的启动过程

搜"S3C24XX NAND Driver"
S3c2410.c (drivers\mtd\nand)

s3c2410_nand_inithw
s3c2410_nand_init_chip
nand_scan  // 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            

3 nand flash驱动程序框架

(1)分配一个nand_chip/mtd_info结构体

(2)设置

(3)硬件相关的操作

(4)使用nand_scan/add_mtd_partitions

4 写代码

参考drivers\mtd\nand\s3c2410.c

  1 /*参考drivers\mtd\nand\at91_nand.c*/
  2 
  3 
  4 #include <linux/module.h>
  5 #include <linux/types.h>
  6 #include <linux/init.h>
  7 #include <linux/kernel.h>
  8 #include <linux/string.h>
  9 #include <linux/ioport.h>
 10 #include <linux/platform_device.h>
 11 #include <linux/delay.h>
 12 #include <linux/err.h>
 13 #include <linux/slab.h>
 14 #include <linux/clk.h>
 15 
 16 #include <linux/mtd/mtd.h>
 17 #include <linux/mtd/nand.h>
 18 #include <linux/mtd/nand_ecc.h>
 19 #include <linux/mtd/partitions.h>
 20 
 21 #include <asm/io.h>
 22 
 23 #include <asm/arch/regs-nand.h>
 24 #include <asm/arch/nand.h>
 25 
 26 
 27 struct s3c_nand_regs {
 28     unsigned long nfconf  ;
 29     unsigned long nfcont  ;
 30     unsigned long nfcmd   ;
 31     unsigned long nfaddr  ;
 32     unsigned long nfdata  ;
 33     unsigned long nfeccd0 ;
 34     unsigned long nfeccd1 ;
 35     unsigned long nfeccd  ;
 36     unsigned long nfstat  ;
 37     unsigned long nfestat0;
 38     unsigned long nfestat1;
 39     unsigned long nfmecc0 ;
 40     unsigned long nfmecc1 ;
 41     unsigned long nfsecc  ;
 42     unsigned long nfsblk  ;
 43     unsigned long nfeblk  ;
 44 };
 45 
 46 static struct mtd_info *s3c_mtd;
 47 static struct nand_chip *s3c_nand;
 48 
 49 
 50 static struct mtd_partition s3c_nand_parts[] = {
 51     [0] = {
 52         .name   = "bootloader",
 53         .size   = 0x00040000,
 54         .offset    = 0,
 55     },
 56     [1] = {
 57         .name   = "params",
 58         .offset = MTDPART_OFS_APPEND,
 59         .size   = 0x00020000,
 60     },
 61     [2] = {
 62         .name   = "kernel",
 63         .offset = MTDPART_OFS_APPEND,
 64         .size   = 0x00200000,
 65     },
 66     [3] = {
 67         .name   = "root",
 68         .offset = MTDPART_OFS_APPEND,
 69         .size   = MTDPART_SIZ_FULL,
 70     }
 71 };
 72 
 73 static void s3c2440_select_chip(struct mtd_info *mtd, int chipnr)
 74 {
 75     if (chipnr == -1)
 76     {
 77         /* 取消选中: NFCONT[1]设为1 */
 78         s3c_nand_regs->nfcont |= (1<<1);        
 79     }
 80     else
 81     {
 82         /* 选中: NFCONT[1]设为0 */
 83         s3c_nand_regs->nfcont &= ~(1<<1);
 84     }
 85 }
 86 
 87 static void s3c2440_cmd_ctrl(struct mtd_info *mtd, int dat, unsigned int ctrl)
 88 {
 89     if (ctrl & NAND_CLE)
 90     {
 91         /* 发命令: NFCMMD=dat */
 92         s3c_nand_regs->nfcmd = dat;
 93     }
 94     else
 95     {
 96         /* 发地址: NFADDR=dat */
 97         s3c_nand_regs->nfaddr = dat;
 98     }
 99 }
100 
101 static int s3c2440_dev_ready(struct mtd_info *mtd)
102 {
103     return (s3c_nand_regs->nfstat & (1<<0));
104 }
105 
106 
107 static int s3c_nand_init(void)
108 {
109     struct clk *clk;
110     s3c_nand = kzalloc(sizeof(struct nand_chip), GFP_KERNEL);
111 
112     s3c_nand_regs = ioremap(0x4E000000, sizeof(struct s3c_nand_regs));
113 
114     s3c_nand->select_chip = s3c2440_select_chip;
115     s3c_nand->cmd_ctrl = s3c2440_cmd_ctrl;
116     s3c_nand->IO_ADDR_R = &s3c_nand_regs->nfdata;
117     s3c_nand->IO_ADDR_W = &s3c_nand_regs->nfdata;
118     s3c_nand->dev_ready   = s3c2440_dev_ready;
119     s3c_nand->ecc.mode    = NAND_ECC_SOFT;//enable ECC
120     
121     clk = clk_get(NULL, "nand");
122     clk_enable(clk);              
123 
124 #define TACLS    0
125 #define TWRPH0   1
126 #define TWRPH1   0
127     s3c_nand_regs->nfconf = (TACLS<<12) | (TWRPH0<<8) | (TWRPH1<<4);
128     s3c_nand_regs->nfcont = (1<<1) | (1<<0);
129     
130     s3c_mtd = kzalloc(sizeof(struct nand_chip), GFP_KERNEL);
131     s3c_mtd->owner = THIS_MODULE;
132     s3c_mtd->priv = s3c_nand;
133     nand_scan(s3c_mtd, 1);//识别nand falsh,构造mtd_info
134 
135     add_mtd_partitions(s3c_mtd, s3c_nand_parts,4);
136 
137     return 0;
138 }
139 
140 
141 static void s3c_nand_exit(void)
142 {
143     del_mtd_partitions(s3c_mtd);
144     kfree(s3c_mtd);
145     iounmap(s3c_nand_regs);
146     kfree(s3c_nand);
147 }
148 
149 module_init(s3c_nand_init);
150 module_exit(s3c_nand_exit);
151 
152 MODULE_LICENSE("GPL");
s3c_nand.c

 


作者:wade_linux,发布于:2018/08/28
原文:https://www.cnblogs.com/Lwd-linux/p/6283263.html