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");
