NAND FLASH设备驱动：平台-设备-驱动模型
platform: linux-2.6.22.6
0
概述
FLASH在嵌入式系统中是必不可少的，它是bootloader、linux内核和文件系统的最佳载体。在Linux内核中引入了MTD子系统为NOR FLASH和NAND FLASH设备提供统一的接口，从而使得FLASH驱动的设计大为简化。
在引入MTD后Linux系统中FLASH设备驱动可分为四层，如图：
1. 硬件驱动层
FLASH硬件驱动层负责FLASH硬件设备的读、写、擦出，LINUX MTD设备的NOR FLASH驱动位于/driver/mtd/chips子目录下，NAND FLASH驱动则位于/driver/mtd/nand子目录下。
2. MTD原始设备层：MTD原始设备层由两部分构成，一部分是MTD原始设备的通用代码(mtdcore.c、mtdpart.c)，另一部分是各个特定的FLASH的数据，例如分区。
3. MTD设备层：基于MTD原始设备，LINUX系统可以定义出MTD的块设备（主设备号31）和字符设备（设备号90），构成设备层。MTD字符设备在mtdchar.c实现，MTD块设备在mtdblock.c实现。
4. 设备节点：通过mknod在/dev子目录下建立MTD字符设备节点（主设备号为90）和块设备节点（主设备号为31），用户通过访问此设备节点即可访问MTD字符设备和块设备。
也可通过下图理解：
工作流程：
当应用层要求对FLASH进行读写时：它会向MTD设备层发出请求，设备层的读写函数会调用MTD原始设备层中的读写函数，即mtd_info结构体（mtd原始设备层中描述设备的专用结构体）中的读写函数，而mtd_info中的函数会调用nand_chip（nand硬件驱动层中描述设备的结构体，其中包含了针对特定设备的基本参数和设备操作函数）中的读写函数。所以当我们写一个flash硬件驱动程序时，有以下步骤：
1. 如果FLASH要分区，则定义mtd_partition数组，将FLASH分区信息记录其中。
2. 在模块加载时为每一个chip(主分区)分配mtd_info和nand_chip的内存，根据目标板nand 控制器的特殊情况初始化nand_chip中的实现对FLASH操作的成员函数，如hwcontrol()、dev_ready()、read_byte()、write_byte()等。填充mtd_info，并将其priv成员指向nand_chip。
3. 以mtd_info为参数调用nand_scan()函数探测NAND FLASH的存在。nand_scan()函数会从FLASH芯片中读取其参数，填充相应nand_chip成员。
4. 如果要分区，则以mtd_info和mtd_partition为参数调用add_mtd_partions(),添加分区信息。在这个函数里面会为每一个分区（不包含主分区）分配一个mtd_info结构体，填充，并注册。
1. NAND flash设备注册过程:
1.1 NAND FLASH设备的定义：\arch\arm\plat-s3c24xx\devs.c
static struct resource s3c_nand_resource[] = {
[0] = {
.start = S3C2410_PA_NAND,
.end = S3C2410_PA_NAND + S3C24XX_SZ_NAND - 1,
.flags = IORESOURCE_MEM,
}
};
struct platform_device s3c_device_nand = {
.name = "s3c2410-nand",
.id = -1,
.num_resources = ARRAY_SIZE(s3c_nand_resource),
.resource = s3c_nand_resource,
};
1.2 平台设备数组定义：\arch\arm\plat-s3c24xx\common-smdk.c
static struct platform_device __initdata *smdk_devs[] = {
&s3c_device_nand,
&smdk_led4,
&smdk_led5,
&smdk_led6,
&smdk_led7,
};
static void __init smdk2410_init(void)
void __init smdk_machine_init(void)
platform_add_devices(smdk_devs, ARRAY_SIZE(smdk_devs));
platform_device_register(devs[i]); // 注册设备：s3c_device_nand
2. NAND FLASH设备驱动注册过程：
2.1 设备驱动定义：
static struct platform_driver s3c2410_nand_driver = {
.probe = s3c2410_nand_probe,
.remove = s3c2410_nand_remove,
.suspend = s3c24xx_nand_suspend,
.resume = s3c24xx_nand_resume,
.driver = {
.name = "s3c2410-nand", // 看名字是不是和设备定义一致的
.owner = THIS_MODULE,
},
};
2.2 NAND FLASH设备驱动注册流程
module_init(s3c2410_nand_init);
static int __init s3c2410_nand_init(void)
platform_driver_register(&s3c2410_nand_driver) // 完成s3c2410_nand_driver的注册
3. probe函数过程：
前面分析过，在总线-设备-驱动平台中，比较.name，如果相等，则调用驱动下面的probe函数，
即调用函数：s3c2410_nand_probe
static int s3c2410_nand_probe(struct platform_device *dev)
s3c24xx_nand_probe(dev, TYPE_S3C2410);
struct s3c2410_nand_info *info;
info = kmalloc(sizeof(*info), GFP_KERNEL);
// 设置时钟
info->clk = clk_get(&pdev->dev, "nand");
clk_enable(info->clk);
// 获取资源变量
info->regs = ioremap(res->start, size);
// 初始化硬件
err = s3c2410_nand_inithw(info, pdev);
// 分配mtd
info->mtds = kmalloc(size, GFP_KERNEL);
// 初始化MTD原始设备对应的芯片
s3c2410_nand_init_chip(info, nmtd, sets);
// 扫描NAND设备
nand_scan(&nmtd->mtd, (sets) ? sets->nr_chips : 1);
nand_scan_ident(mtd, maxchips);
nand_scan_tail(mtd);
// 添加分区信息
s3c2410_nand_add_partition(info, nmtd, sets);
add_mtd_device(&mtd->mtd);
list_for_each(this, &mtd_notifiers) {
struct mtd_notifier *not = list_entry(this, struct mtd_notifier, list);
not->add(mtd);
4. 相关数据结构体
4.1 struct s3c2410_nand_info：
表示一个NAND FLASH控制器的相关信息，包括：控制器的硬件信息，MTD原始设备信息，分区信息，
所使用的资源，以及工作的时钟频率等。
struct s3c2410_nand_info {
/* mtd info */
struct nand_hw_control controller;
struct s3c2410_nand_mtd *mtds;
struct s3c2410_platform_nand *platform;
/* device info */
struct device *device;
struct resource *area;
struct clk *clk;
void __iomem *regs;
void __iomem *sel_reg;
int sel_bit;
int mtd_count;
enum s3c_cpu_type cpu_type;
};
4.2 struct s3c2410_nand_mtd：
主要定义了该NAND FLASH芯片对应的MTD原始设备，物理NAND FLASH芯片以及对应的NAND FLASH控制器。
struct s3c2410_nand_mtd {
struct mtd_info mtd; // 表示MTD原始设备
struct nand_chip chip; // 表示硬件驱动层：对应的物理NAND FLASH芯片
struct s3c2410_nand_set *set; // 分区信息表
struct s3c2410_nand_info *info; // NADN FLASH控制器
int scan_res;
};
4.3 struct mtd_info：
定义了MTD原始设备层相关的参数和函数接口。
struct mtd_info {
u_char type;
u_int32_t flags;
u_int32_t size; // Total size of the MTD
/* "Major" erase size for the device. Na茂ve users may take this
* to be the only erase size available, or may use the more detailed
* information below if they desire
*/
u_int32_t erasesize;
/* Minimal writable flash unit size. In case of NOR flash it is 1 (even
* though individual bits can be cleared), in case of NAND flash it is
* one NAND page (or half, or one-fourths of it), in case of ECC-ed NOR
* it is of ECC block size, etc. It is illegal to have writesize = 0.
* Any driver registering a struct mtd_info must ensure a writesize of
* 1 or larger.
*/
u_int32_t writesize;
u_int32_t oobsize; // Amount of OOB data per block (e.g. 16)
u_int32_t oobavail; // Available OOB bytes per block
// Kernel-only stuff starts here.
char *name;
int index;
/* ecc layout structure pointer - read only ! */
struct nand_ecclayout *ecclayout;
/* Data for variable erase regions. If numeraseregions is zero,
* it means that the whole device has erasesize as given above.
*/
int numeraseregions;
struct mtd_erase_region_info *eraseregions;
int (*erase) (struct mtd_info *mtd, struct erase_info *instr);
/* This stuff for eXecute-In-Place */
int (*point) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char **mtdbuf);
/* We probably shouldn't allow XIP if the unpoint isn't a NULL */
void (*unpoint) (struct mtd_info *mtd, u_char * addr, loff_t from, size_t len);
int (*read) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
int (*write) (struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf);
int (*read_oob) (struct mtd_info *mtd, loff_t from,
struct mtd_oob_ops *ops);
int (*write_oob) (struct mtd_info *mtd, loff_t to,
struct mtd_oob_ops *ops);
/*
* Methods to access the protection register area, present in some
* flash devices. The user data is one time programmable but the
* factory data is read only.
*/
int (*get_fact_prot_info) (struct mtd_info *mtd, struct otp_info *buf, size_t len);
int (*read_fact_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
int (*get_user_prot_info) (struct mtd_info *mtd, struct otp_info *buf, size_t len);
int (*read_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
int (*write_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf);
int (*lock_user_prot_reg) (struct mtd_info *mtd, loff_t from, size_t len);
/* kvec-based read/write methods.
NB: The 'count' parameter is the number of _vectors_, each of
which contains an (ofs, len) tuple.
*/
int (*writev) (struct mtd_info *mtd, const struct kvec *vecs, unsigned long count, loff_t to, size_t *retlen);
/* Sync */
void (*sync) (struct mtd_info *mtd);
/* Chip-supported device locking */
int (*lock) (struct mtd_info *mtd, loff_t ofs, size_t len);
int (*unlock) (struct mtd_info *mtd, loff_t ofs, size_t len);
/* Power Management functions */
int (*suspend) (struct mtd_info *mtd);
void (*resume) (struct mtd_info *mtd);
/* Bad block management functions */
int (*block_isbad) (struct mtd_info *mtd, loff_t ofs);
int (*block_markbad) (struct mtd_info *mtd, loff_t ofs);
struct notifier_block reboot_notifier; /* default mode before reboot */
/* ECC status information */
struct mtd_ecc_stats ecc_stats;
/* Subpage shift (NAND) */
int subpage_sft;
void *priv;
struct module *owner;
int usecount;
/* If the driver is something smart, like UBI, it may need to maintain
* its own reference counting. The below functions are only for driver.
* The driver may register its callbacks. These callbacks are not
* supposed to be called by MTD users */
int (*get_device) (struct mtd_info *mtd);
void (*put_device) (struct mtd_info *mtd);
};
4.4 struct nand_chip：
定义了具体的物理NAND FLASH芯片最底层的硬件接口操作函数及硬件相关信息。
主要包括：NAND FLASH芯片所在的读写I/O地址，读写函数，NAND FLASH芯片容量以及坏块的模式等。
struct nand_chip {
void __iomem *IO_ADDR_R;
void __iomem *IO_ADDR_W;
uint8_t (*read_byte)(struct mtd_info *mtd);
u16 (*read_word)(struct mtd_info *mtd);
void (*write_buf)(struct mtd_info *mtd, const uint8_t *buf, int len);
void (*read_buf)(struct mtd_info *mtd, uint8_t *buf, int len);
int (*verify_buf)(struct mtd_info *mtd, const uint8_t *buf, int len);
void (*select_chip)(struct mtd_info *mtd, int chip);
int (*block_bad)(struct mtd_info *mtd, loff_t ofs, int getchip);
int (*block_markbad)(struct mtd_info *mtd, loff_t ofs);
void (*cmd_ctrl)(struct mtd_info *mtd, int dat,
unsigned int ctrl);
int (*dev_ready)(struct mtd_info *mtd);
void (*cmdfunc)(struct mtd_info *mtd, unsigned command, int column, int page_addr);
int (*waitfunc)(struct mtd_info *mtd, struct nand_chip *this);
void (*erase_cmd)(struct mtd_info *mtd, int page);
int (*scan_bbt)(struct mtd_info *mtd);
int (*errstat)(struct mtd_info *mtd, struct nand_chip *this, int state, int status, int page);
int (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
const uint8_t *buf, int page, int cached, int raw);
int chip_delay;
unsigned int options;
int page_shift;
int phys_erase_shift;
int bbt_erase_shift;
int chip_shift;
int numchips;
unsigned long chipsize;
int pagemask;
int pagebuf;
int subpagesize;
uint8_t cellinfo;
int badblockpos;
nand_state_t state;
uint8_t *oob_poi;
struct nand_hw_control *controller;
struct nand_ecclayout *ecclayout;
struct nand_ecc_ctrl ecc;
struct nand_buffers *buffers;
struct nand_hw_control hwcontrol;
struct mtd_oob_ops ops;
uint8_t *bbt;
struct nand_bbt_descr *bbt_td;
struct nand_bbt_descr *bbt_md;
struct nand_bbt_descr *badblock_pattern;
void *priv;
};
4.5 struct s3c2410_nand_set：定义了NAND FLASH芯片的分区信息和名字。
/* struct s3c2410_nand_set
*
* define an set of one or more nand chips registered with an unique mtd
*
* nr_chips = number of chips in this set
* nr_partitions = number of partitions pointed to be partitoons (or zero)
* name = name of set (optional)
* nr_map = map for low-layer logical to physical chip numbers (option)
* partitions = mtd partition list
*/
struct s3c2410_nand_set {
int nr_chips;
int nr_partitions;
char *name;
int *nr_map;
struct mtd_partition *partitions;
};
比如在：\arch\arm\plat-s3c24xx\common-smdk.c 定义了数组，每一个数组元素表示一个NAND FLASH芯片的分区信息。
static struct s3c2410_nand_set smdk_nand_sets[] = {
[0] = {
.name = "NAND", // 芯片集合的名字
.nr_chips = 1, // 芯片集合的数量 = 1
.nr_partitions = ARRAY_SIZE(smdk_default_nand_part), // 分区个数
.partitions = smdk_default_nand_part, // 分区信息表
},
};
// 具体的分区信息表
static struct mtd_partition smdk_default_nand_part[] = {
[0] = {
.name = "Boot Agent",
.size = SZ_16K,
.offset = 0,
},
[1] = {
.name = "S3C2410 flash partition 1",
.offset = 0,
.size = SZ_2M,
},
[2] = {
.name = "S3C2410 flash partition 2",
.offset = SZ_4M,
.size = SZ_4M,
},
[3] = {
.name = "S3C2410 flash partition 3",
.offset = SZ_8M,
.size = SZ_2M,
},
[4] = {
.name = "S3C2410 flash partition 4",
.offset = SZ_1M * 10,
.size = SZ_4M,
},
[5] = {
.name = "S3C2410 flash partition 5",
.offset = SZ_1M * 14,
.size = SZ_1M * 10,
},
[6] = {
.name = "S3C2410 flash partition 6",
.offset = SZ_1M * 24,
.size = SZ_1M * 24,
},
[7] = {
.name = "S3C2410 flash partition 7",
.offset = SZ_1M * 48,
.size = SZ_16M,
}
};
参考博客：
1. Linux NAND FLASH驱动框架分析---mtd
2. Linux NAND FLASH驱动框架分析--实例
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