Arm嵌入式开发之Flash设备驱动

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Linux MTD系统层次

引入了MTD后,linux中的flash设备驱动及接口分为四个层,从上到下:设备节点,MTD设备层,MTD原始设备层,硬件驱动层。

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.cmtdpart.c),另一部分是各个特定的FLASH的数据,示例分区。

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31www.linuxidc.com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/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。

从上图可以看出,MTD设备层与原始设备层打交道。通过分析源代码我们可以知道当上层要求对FLASH进行读写时,它会像设备层发出请求,设备层的读写函数会调用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_chipnand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_infonand_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.
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_infomtd_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。

 

struct mtd_info
{

u_char type;//内存技术的类型

u_int32_t flags;//标志位

u_int32_t size;  // Total size of the MTD

u_int32_t erasesize;

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;

 struct nand_ecclayout *ecclayout;

int numeraseregions;

struct mtd_erase_region_info *eraseregions;

int (*erase) (struct mtd_info *mtd, struct erase_info *instr);

int (*point) (struct mtd_info *mtd, loff_t from, size_t len,

size_t *retlen, void **virt, resource_size_t *phys);

void (*unpoint) (struct mtd_info *mtd, 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 (*panic_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);

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);

int (*writev) (struct mtd_info *mtd, const struct kvec *vecs, unsigned long count, loff_t to, size_t *retlen);

void (*sync) (struct mtd_info *mtd);

int (*lock) (struct mtd_info *mtd, loff_t ofs, size_t len);

int (*unlock) (struct mtd_info *mtd, loff_t ofs, size_t len);

 /*
能量管理函数*/

int (*suspend) (struct mtd_info *mtd);

void (*resume) (struct mtd_info *mtd);

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; 

struct mtd_ecc_stats ecc_stats;

int subpage_sft;

void *priv;

struct module *owner;

int usecount;

int (*get_device) (struct mtd_info *mtd);

void (*put_device) (struct mtd_info *mtd);

};

 

MTD用户控件编程

Mtdchar.c实现了字符设备接口。通过read(),write()系统调用可读写flash,通过一系列IOCTL命令可获取flash设备信息,擦除flash,读写NANDOOB,获取OOBlayout及检查NAND坏块等。

static int mtd_ioctl(struct inode *inode, struct file *file,

             
    
u_int cmd, u_long arg)

struct mtd_info *mtd = (struct mtd_info *)file->private_data;

      
int ret = 0;

      
u_long size;

      

      
DEBUG(MTD_DEBUG_LEVEL0, "MTD_ioctln");

 

      
size = (cmd & IOCSIZE_MASK) >> IOCSIZE_SHIFT;

      
if (cmd & IOC_IN) {

             
ret = verify_area(VERIFY_READ, (char *)arg, size);

             
if (ret) return ret;

      
}

      
if (cmd & IOC_OUT) {

             
ret = verify_area(VERIFY_WRITE, (char *)arg, size);

             
if (ret) return ret;

      
}

      

      
switch (cmd) {

      
case MEMGETREGIONCOUNT:

             
if (copy_to_user((int *) arg, &(mtd->numeraseregions), sizeof(int)))

                    
return -EFAULT;

             
break;

             

NOR flash设备编程直接利用Mtdchar.c定义的设备接口,利用mtd_info中的成员函数来操作。但NAND Flash有自己的驱动内核,通过/driver/mtd/nand/nand_base.c实现,不再用mtd_info数据结构,而转到了nand_chip数据结构。

 

NOR Flash驱动程序实例分析

#define WINDOW_ADDR 0x01000000     
/* NOR FLASH
物理地址 */

#define WINDOW_SIZE 0x800000        
/* NOR FLASH
大小 */

#define BUSWIDTH   
2

/*
探测的接口类型可以是"cfi_probe",
"jedec_probe", "map_rom", NULL }; */

#define PROBETYPES { "cfi_probe", NULL }

 

#define MSG_PREFIX "S3C2410-NOR:"  
/* prefix for our printk()'s */

#define MTDID     
"s3c2410-nor"    /* for mtdparts= partitioning */

 

static struct mtd_info *mymtd;

 

struct map_info s3c2410nor_map = 
// map_info

{

 
.name = "NOR flash on S3C2410",

 
.size = WINDOW_SIZE,

 
.bankwidth = BUSWIDTH,

 
.phys = WINDOW_ADDR,

};

 

#ifdef CONFIG_MTD_PARTITIONS

 
/* MTD
分区信息 
*/

 
static struct mtd_partition static_partitions[] =

 
{

   
{

     
.name = "BootLoader", .size = 0x040000, .offset = 0x0  //bootloader
存放的区域

   
} ,

   
{

     
.name = "Kernel", .size = 0x0100000, .offset = 0x40000 //
内核映像存放的区域

   
}

   
,

   
{

     
.name = "RamDisk", .size = 0x400000, .offset = 0x140000 //ramdisk
存放的区域

   
}

   
,

   
{

     
.name = "cramfs(2MB)", .size = 0x200000, .offset = 0x540000 //
只读的cramfs区域

   
}

   
,

   
{

     
.name = "jffs2(0.75MB)", .size = 0xc0000, .offset = 0x740000 //
可读写的jffs2区域

   
}

   
,

 
};

#endif

 

static int mtd_parts_nb = 0;

static struct mtd_partition *mtd_parts = 0;

 

int __init init_s3c2410nor(void)

{

 
static const char *rom_probe_types[] = PROBETYPES;

 
const char **type;

 
const char *part_type = 0;

 

 
printk(KERN_NOTICE MSG_PREFIX "0x%08x at 0x%08xn", WINDOW_SIZE, WINDOW_ADDR);

 
s3c2410nor_map.virt = ioremap(WINDOW_ADDR, WINDOW_SIZE);//
物理->虚拟地址

 

 
if (!s3c2410nor_map.virt)

 
{

   
printk(MSG_PREFIX "failed to ioremapn");

   
return  - EIO;

 
}

 

 
simple_map_init(&s3c2410nor_map);

 

 
mymtd = 0;

 
type = rom_probe_types;

 
for (; !mymtd &&  *type; type++)

 
{

  
 mymtd = do_map_probe(*type, &s3c2410nor_map);//
探测NOR
FLASH
do_map_probe
()

//定义在drivers/mtd/chips/chipreg.c

 
}

 
if (mymtd)

 
{

   
mymtd->owner = THIS_MODULE;

 

   
#ifdef CONFIG_MTD_PARTITIONS

   
  mtd_parts_nb = parse_mtd_partitions(mymtd, NULL, &mtd_parts, MTDID);//
探测分区信息

     
if (mtd_parts_nb > 0)

       
part_type = "detected";

 

     
if (mtd_parts_nb == 0) //
未探测到使用数组定义的分区信息

     
{

       
mtd_parts = static_partitions;

       
mtd_parts_nb = ARRAY_SIZE(static_partitions);

       
part_type = "static";

     
}

   
#endif

   
add_mtd_device(mymtd);

   
if (mtd_parts_nb == 0)

     
printk(KERN_NOTICE MSG_PREFIX "no partition info availablen");

   
else

   
{

     
printk(KERN_NOTICE MSG_PREFIX "using %s partition definitionn",

       
part_type);

     
add_mtd_partitions(mymtd, mtd_parts, mtd_parts_nb);//
添加分区信息

   
}

   
return 0;

 
}

 

 
iounmap((void*)s3c2410nor_map.virt);

 
return  - ENXIO;

}

 

static void __exit cleanup_s3c2410nor(void)

{

 
if (mymtd)

 
{

   
del_mtd_partitions(mymtd);  //
删除分区

   
del_mtd_device(mymtd);   //
删除设备

   
map_destroy(mymtd);    

 
}

 
if (s3c2410nor_map.virt)

 
{

   
iounmap((void*)s3c2410nor_map.virt);

   
s3c2410nor_map.virt = 0;

 
}

}

 

NAND flash驱动程序实例分析

我们以2.6.26内核中s3c2410nand
flash
驱动程序为例来分析一下这个过程,这里的flash驱动被写成了platform驱动的形式。我们下面分析其过程:

1.
注册nand flash设备

nand flash分区:

linux2.6.26.8/arch/arm/plat-s3c24xx/common-smdk.c:

static struct mtd_partition smdk_default_nand_part[] = {

[0] = {

name: "bootloader",

size: 0x00100000,

offset: 0x0,

},

[1] = {

name: "kernel",

size: 0x00300000,

offset: 0x00100000,

},

[2] = {

name: "root",

size: 0x02800000,

offset: 0x00400000,

},

};

static struct s3c2410_nand_set smdk_nand_sets[] = {  //该数组为chip集合,这里我们只有一片chip

[0] = {

.name = "NAND",

.nr_chips = 1,

.nr_partitions = ARRAY_SIZE(smdk_default_nand_part),

.partitions = smdk_default_nand_part,

},

};

static struct s3c2410_platform_nand smdk_nand_info = {  //这里将许多数据作为platform_data传入包括chip数组

.tacls = 20,

.twrph0 = 60,

.twrph1 = 20,

.nr_sets = ARRAY_SIZE(smdk_nand_sets),

.sets = smdk_nand_sets,

};

nand控制器资源:

linux2.6.26.8/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,

};

注册nand flash作为platform
device:

linux2.6.26.8/arch/arm/plat-s3c24xx/common-smdk.c:

static struct platform_device __initdata *smdk_devs[] = {

&s3c_device_nand,

};

void __init smdk_machine_init(void)

{

s3c_device_nand.dev.platform_data = &smdk_nand_info;   //注意这里的赋值,在nand 
flash
驱动程序的probe函数里面利用了这里赋值的数据

platform_add_devices(smdk_devs, ARRAY_SIZE(smdk_devs));

s3c2410_pm_init();

}

2.注册nand flash driver
linux/drivers/mtd/nand/s3c2410.c:

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",

.owner = THIS_MODULE,

},

};

static int __init s3c2410_nand_init(void)

{

printk("S3C24XX NAND Driver, (c) 2004 Simtec Electronicsn");

 

platform_driver_register(&s3c2412_nand_driver);

platform_driver_register(&s3c2440_nand_driver);

return platform_driver_register(&s3c2410_nand_driver);

}

module_init(s3c2410_nand_init);

platform_driver驱动被加载时或者是当platform_device被注册时,总线驱动程序

会查找与设备匹配的驱动程序,找到时设备驱动程序的probe函数会被调用,下面我们来分析一下在我们驱动程序中的probe函数:

static int s3c2410_nand_probe(struct platform_device *dev)

{

return s3c24xx_nand_probe(dev, TYPE_S3C2410);

}

static int s3c24xx_nand_probe(struct platform_device *pdev,

      enum s3c_cpu_type cpu_type)

{

struct s3c2410_platform_nand *plat = to_nand_plat(pdev);

struct s3c2410_nand_info *info;

struct s3c2410_nand_mtd *nmtd;

struct s3c2410_nand_set *sets;

struct resource *res;

int err = 0;

int size;

int nr_sets;

int setno;

pr_debug("s3c2410_nand_probe(%p)n", pdev);

info = kmalloc(sizeof(*info), GFP_KERNEL);  //分配s3c2410_nand_info内存

if (info == NULL) {

dev_err(&pdev->dev, "no memory for flash infon");

err = -ENOMEM;

goto exit_error;

}

memzero(info, sizeof(*info));         //s3c2410_nand_info清零

platform_set_drvdata(pdev, info); //pdev->dev->driver_data = info

spin_lock_init(&info->controller.lock);

init_waitqueue_head(&info->controller.wq);

 info->clk = clk_get(&pdev->dev, "nand");

if (IS_ERR(info->clk)) {

dev_err(&pdev->dev, "failed to get clockn");

err = -ENOENT;

goto exit_error;

}

clk_enable(info->clk);

res  = pdev->resource;

size = res->end - res->start + 1;

info->area = request_mem_region(res->start, size, pdev->name);

 if (info->area == NULL) {

dev_err(&pdev->dev, "cannot reserve register regionn");

err = -ENOENT;

goto exit_error;

}

info->device     = &pdev->dev;

info->platform   = plat;

info->regs       = ioremap(res->start, size);  //存储nand控制器寄存器虚拟地

info->cpu_type   = cpu_type;

if (info->regs == NULL) {

dev_err(&pdev->dev, "cannot reserve register regionn");

err = -EIO;

goto exit_error;

}

dev_dbg(&pdev->dev, "mapped registers at %pn", info->regs);

err = s3c2410_nand_inithw(info, pdev);  //设置TACLS
TWRPH0 TWRPH1

if (err != 0)

goto exit_error;

sets = (plat != NULL) ? plat->sets : NULL;    //sets指向plat->sets数组的首地址

nr_sets = (plat != NULL) ? plat->nr_sets : 1;   //plat->sets中的chips数目

info->mtd_count = nr_sets;

size = nr_sets * sizeof(*info->mtds);     

info->mtds = kmalloc(size, GFP_KERNEL);

if (info->mtds == NULL) {

dev_err(&pdev->dev, "failed to allocate mtd storagen");

err = -ENOMEM;

goto exit_error;

}

memzero(info->mtds, size); //将申请的s3c2410_nand_mtd结构体数组清零

nmtd = info->mtds;

for (setno = 0; setno < nr_sets; setno++, nmtd++) {

pr_debug("initialising set %d (%p, info %p)n", setno, nmtd, info);

s3c2410_nand_init_chip(info, nmtd, sets); //初始化s3c2410_nand_mtd结构

体中的chip成员和mtd成员,mtd.priv
= chip

nmtd->scan_res = nand_scan_ident(&nmtd->mtd,

 (sets) ? sets->nr_chips : 1); //设置nand_chip一些成员

的默认值并探测FLASH,并读出FLASH参数,填入nand_chip

if (nmtd->scan_res == 0) {

s3c2410_nand_update_chip(info, nmtd); //

nand_scan_tail(&nmtd->mtd);   //设置nand_chip中所有未被设置的

函数指针的值,并填充相关mtd_info成员,若需要建立bad
block table

s3c2410_nand_add_partition(info, nmtd, sets);  //添加分区

}

if (sets != NULL)

sets++; //注意这里sets++,指向下一个plat->sets里的set

}

if (allow_clk_stop(info)) {

dev_info(&pdev->dev, "clock idle support enabledn");

clk_disable(info->clk);

}

pr_debug("initialised okn");

return 0;

 exit_error:

s3c2410_nand_remove(pdev);

if (err == 0)

err = -EINVAL;

return err;

}