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作者：彭东林
u-boot版本：u-boot-2015.04
Linux版本：Linux-3.14
硬件平台：tq2440， 内存：64M NandFlash: 256MB
下面我们分两部分，u-boot和kernel，首先介绍u-boot中是如何支持mtdparts的，然后简单分析Linux内核设置分区的两种方式：
方式一
在平台代码中写死，然后在初始化NandFlash的时候设置。
方式二
在u-boot中设置，这个比较灵活，u-boot将分区信息（形如：mtdparts=xxx）添加到bootargs中，kernel在启动的时候会解析mtdparts。
转载自：http://w3sun.blog.163.com/blog/static/1859535342012058369333/
分区方法
1)MTD层的分区
2)通过U-boot传递给内核的命令行中的mtdparts=...
3)其他可以让内核知道分区信息的任何办法，（内核默认的命令参数）
下面说到mtdparts，及它的用法：
mtdparts
mtdparts=fc000000.nor_flash:1920k(linux),128k(fdt),20M(ramdisk),4M(jffs2),382
72k(user),256k(env),384k(uboot)要想这个参数起作用，
内核中的mtd驱动必须要支持，即内核配置时需要选上
Device Drivers --->
Memory Technology Device (MTD) support --->
Command line partition table parsing
mtdparts的格式如下：
mtdparts=<mtddef>[;<mtddef]
<mtddef> := <mtd-id>:<partdef>[,<partdef>]
<partdef> := <size>[@offset][<name>][ro]
<mtd-id> := unique id used in mapping driver/device
<size> := standard linux memsize OR "-" to denote all remaining space
<name> := (NAME)
因此你在使用的时候需要按照下面的格式来设置：
mtdparts=mtd-id:<size1>@<offset1>(<name1>),<size2>@<offset2>(<name2>)
这有几个需要注意的地方：
a.mtd-id 必须要跟你当前平台的flash的mtd-id一致，不然整个mtdparts会失效 怎样获取到
当前平台的flash的mtd-id？在bootargs参数列表中，可以指定当前flash的mtd-id，指定 mtdid
s:nand0=gen_nand.1，前面的nand0则表示第一个flash
b.size在设置的时候可以为实际的size(xxM,xxk,xx)，也可以为‘-‘这表示剩余的所有空间。相
关信息可以查看drivers/mtd/cmdlinepart.c中的注释找到相关描述。
U-boot环境变量有两个，他们分别是： bootcmd 和bootargs。
至于在我们自己的at91sam9263ek板子上为了实现mtdparts分区命令的支持需要在U-boot
-2010.06/include/configs/at91sam9263ek.h中添加相关的宏定义：
#define CONFIG_CMD_MTDPARTS
#define CONFIG_MTD_DEVICE
#define CONFIG_MTD_PARTITIONS
加入MTD分区信息：
#define MTDIDS_DEFAULT "nand0=atmel_nand"
#define MTDPARTS_DEFAULT "mtdparts=atmel_nand:15M@0(cramfs)," \
"15M(jffs2)," \
"30M(yaffs2)," \
"-(user)"
保存后退出，回到根目录，重新make
[root@localhost u-boot-2010.06]#make at91sam9263ek_dataflash_cs0_config
[root@localhost u-boot-2010.06]#make all
将重新编译的u-boot.bin烧到dataflash中，使用mtdparts查看分区：
U-Boot> mtdparts
device nand0 <atmel_nand>, # parts = 4
#: name size offset mask_flags
0: cramfs 0x00f00000 0x00000000 0
1: jffs2 0x00f00000 0x00f00000 0
2: yaffs2 0x01e00000 0x01e00000 0
3: user 0x04400000 0x03c00000 0
active partition: nand0,0 - (cramfs) 0x00f00000 @ 0x00000000
defaults:
mtdids : nand0=atmel_nand
mtdparts: mtdparts=atmel_nand:15M@0(cramfs),15M(jffs2),30M(yaffs2),-(user)
重新设置分区：
U-Boot> setenv mtdparts mtdparts=atmel_nand:30M@0(a),30M(b),-(c)
U-Boot> save
Saving Environment to dataflash...
U-Boot> mtdparts
device nand0 <atmel_nand>, # parts = 3
#: name size offset mask_flags
0: a 0x01e00000 0x00000000 0
1: b 0x01e00000 0x01e00000 0
2: c 0x04400000 0x03c00000 0
active partition: nand0,0 - (a) 0x01e00000 @ 0x00000000
defaults:
mtdids : nand0=atmel_nand
mtdparts: mtdparts=atmel_nand:15M@0(cramfs),15M(jffs2),30M(yaffs2),-(user)
可以看到，我们可以手动设置分区了。最后还要恢复默认。
U-Boot>mtdparts default
相关的内核代码我已经上传到csdn上了，使用git管理，分支是transplant_to_tq2440
git clone git@code.csdn.net:pengdonglin137/linux-3-14-y.git
在此之前我们先看看NandFlash是如何初始化的。
这里采用platform_device和platform_driver架构。
1. platform_device的注册
在arch/arm/mach-s3c24xx/mach-tq2440.c中:
1: static struct platform_device *tq2440_devices[] __initdata = {
2: ...... 3: &s3c_device_nand, 4: }; 5: 6: static void __init tq2440_machine_init(void)
7: { 8: ...... 9: s3c_nand_set_platdata(&tq2440_nand_info); 10: platform_add_devices(tq2440_devices, ARRAY_SIZE(tq2440_devices)); 11: ...... 12: } 13: 14: MACHINE_START(TQ2440, "TQ2440")
15: ........ 16: .init_machine = tq2440_machine_init, 17: ...... 18: MACHINE_END第5行是nand控制器的platform_device;
第10行platform_add_device会将s3c_device_nand注册到系统中;
第9行设置的就是分区相关的信息
1: /* NAND parititon */
2: 3: static struct mtd_partition tq2440_nand_part[] = {
4: [0] = {5: .name = "Boot",
6: .offset = 0, 7: .size = SZ_2M, 8: }, 9: [1] = {10: .name = "Kernel",
11: .offset = SZ_2M, 12: .size = SZ_1M * 3, 13: }, 14: [2] = {15: .name = "Rootfs",
16: .offset = SZ_1M * 5, 17: .size = MTDPART_SIZ_FULL, 18: } 19: }; 20: 21: static struct s3c2410_nand_set tq2440_nand_sets[] = {
22: [0] = {23: .name = "NAND",
24: .nr_chips = 1, 25: .nr_partitions = ARRAY_SIZE(tq2440_nand_part), 26: .partitions = tq2440_nand_part, 27: }, 28: }; 29: 30: /* choose a set of timings which should suit most 512Mbit
31: * chips and beyond.
32: */
33: 34: static struct s3c2410_platform_nand tq2440_nand_info = {
35: .tacls = 10, 36: .twrph0 = 25, 37: .twrph1 = 10, 38: .nr_sets = ARRAY_SIZE(tq2440_nand_sets), 39: .sets = tq2440_nand_sets, 40: };第3行的结构体tq2440_nand_part就是分区信息，容易看出，这里一共分了3个区，分别是Boot、Kernel和Rootfs:
|
Boot (2MB) |
Kernel |
Rootfs (剩余) |
然后将这个分区表存放到了第21行的tq2440_nand_set的元素[0]中，分区表的名字”NAND”，注意这里的名字很重要，将来u-boot中传入的mtdparts中的mtd-id一致。tq2440_nand_sets的每一个元素存放一张分区表；
第34行的结构体tq2440_nand_info中的tacls/twrph0/twrph1用于控制Nand控制器读写NandFlash时的时序参数。
s3c_device_nand是在文件arch/arm/plat-samsung/devs.c
1: /* NAND */
2: 3: #ifdef CONFIG_S3C_DEV_NAND4: static struct resource s3c_nand_resource[] = {
5: [0] = DEFINE_RES_MEM(S3C_PA_NAND, SZ_1M), 6: }; 7: 8: struct platform_device s3c_device_nand = {
9: .name = "s3c2410-nand",
10: .id = -1, 11: .num_resources = ARRAY_SIZE(s3c_nand_resource), 12: .resource = s3c_nand_resource, 13: }; 14: 15: /*
16: * s3c_nand_copy_set() - copy nand set data
17: * @set: The new structure, directly copied from the old.
18: *
19: * Copy all the fields from the NAND set field from what is probably __initdata
20: * to new kernel memory. The code returns 0 if the copy happened correctly or
21: * an error code for the calling function to display.
22: *
23: * Note, we currently do not try and look to see if we‘ve already copied the
24: * data in a previous set.
25: */
26: static int __init s3c_nand_copy_set(struct s3c2410_nand_set *set)
27: {28: void *ptr;
29: int size;
30: 31: size = sizeof(struct mtd_partition) * set->nr_partitions;
32: if (size) {
33: ptr = kmemdup(set->partitions, size, GFP_KERNEL); 34: set->partitions = ptr; 35: 36: if (!ptr)
37: return -ENOMEM;
38: } 39: 40: if (set->nr_map && set->nr_chips) {
41: size = sizeof(int) * set->nr_chips;
42: ptr = kmemdup(set->nr_map, size, GFP_KERNEL); 43: set->nr_map = ptr; 44: 45: if (!ptr)
46: return -ENOMEM;
47: } 48: 49: if (set->ecc_layout) {
50: ptr = kmemdup(set->ecc_layout,51: sizeof(struct nand_ecclayout), GFP_KERNEL);
52: set->ecc_layout = ptr; 53: 54: if (!ptr)
55: return -ENOMEM;
56: } 57: 58: return 0;
59: } 60: 61: void __init s3c_nand_set_platdata(struct s3c2410_platform_nand *nand)
62: {63: struct s3c2410_platform_nand *npd;
64: int size;
65: int ret;
66: 67: /* note, if we get a failure in allocation, we simply drop out of the
68: * function. If there is so little memory available at initialisation
69: * time then there is little chance the system is going to run.
70: */
71: 72: npd = s3c_set_platdata(nand, sizeof(struct s3c2410_platform_nand),
73: &s3c_device_nand);74: if (!npd)
75: return;
76: 77: /* now see if we need to copy any of the nand set data */
78: 79: size = sizeof(struct s3c2410_nand_set) * npd->nr_sets;
80: if (size) {
81: struct s3c2410_nand_set *from = npd->sets;
82: struct s3c2410_nand_set *to;
83: int i;
84: 85: to = kmemdup(from, size, GFP_KERNEL);86: npd->sets = to; /* set, even if we failed */
87: 88: if (!to) {
89: printk(KERN_ERR "%s: no memory for sets\n", __func__);
90: return;
91: } 92: 93: for (i = 0; i < npd->nr_sets; i++) {
94: ret = s3c_nand_copy_set(to);95: if (ret) {
96: printk(KERN_ERR "%s: failed to copy set %d\n",
97: __func__, i);98: return;
99: } 100: to++; 101: } 102: } 103: }104: #endif /* CONFIG_S3C_DEV_NAND */
第72行将nand(也就是tq2440_nand_info)的副本存放到s3c_device_nand的dev.platform_data中，然后将nand的副本首地址npd返回；
第79行到第100行将tq2440_nand_info的分区信息拷贝一份，赋值给npd的sets成员；
2. platform_driver的注册
文件：drivers/mtd/nand/s3c2410.c
1: /* driver device registration */
2: 3: static struct platform_device_id s3c24xx_driver_ids[] = {
4: {5: .name = "s3c2410-nand",
6: .driver_data = TYPE_S3C2410, 7: }, {8: .name = "s3c2440-nand",
9: .driver_data = TYPE_S3C2440, 10: }, {11: .name = "s3c2412-nand",
12: .driver_data = TYPE_S3C2412, 13: }, {14: .name = "s3c6400-nand",
15: .driver_data = TYPE_S3C2412, /* compatible with 2412 */
16: }, 17: { } 18: }; 19: 20: MODULE_DEVICE_TABLE(platform, s3c24xx_driver_ids); 21: 22: static struct platform_driver s3c24xx_nand_driver = {
23: .probe = s3c24xx_nand_probe, 24: .remove = s3c24xx_nand_remove, 25: .suspend = s3c24xx_nand_suspend, 26: .resume = s3c24xx_nand_resume, 27: .id_table = s3c24xx_driver_ids, 28: .driver = {29: .name = "s3c24xx-nand",
30: .owner = THIS_MODULE, 31: }, 32: }; 33: 34: module_platform_driver(s3c24xx_nand_driver);当注册s3c24xx_nand_driver的时候，由于s3c24xx_driver_ids中的”s3c2410-nand”与s3c_device_nand的name一致，因此函数s3c24xx_nand_probe被执行。
下面我们简要分析函数s3c24xx_nand_probe的实现：
1: /* s3c24xx_nand_probe
2: *
3: * called by device layer when it finds a device matching
4: * one our driver can handled. This code checks to see if
5: * it can allocate all necessary resources then calls the
6: * nand layer to look for devices
7: */
8: static int s3c24xx_nand_probe(struct platform_device *pdev)
9: {10: struct s3c2410_platform_nand *plat = to_nand_plat(pdev);
11: enum s3c_cpu_type cpu_type;
12: struct s3c2410_nand_info *info;
13: struct s3c2410_nand_mtd *nmtd;
14: struct s3c2410_nand_set *sets;
15: struct resource *res;
16: int err = 0;
17: int size;
18: int nr_sets;
19: int setno;
20: 21: cpu_type = platform_get_device_id(pdev)->driver_data; 22: 23: pr_debug("s3c2410_nand_probe(%p)\n", pdev);
24: 25: info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
26: if (info == NULL) {
27: err = -ENOMEM;28: goto exit_error;
29: } 30: 31: platform_set_drvdata(pdev, info); 32: 33: spin_lock_init(&info->controller.lock);
34: init_waitqueue_head(&info->controller.wq); 35: 36: /* get the clock source and enable it */
37: 38: info->clk = devm_clk_get(&pdev->dev, "nand");
39: if (IS_ERR(info->clk)) {
40: dev_err(&pdev->dev, "failed to get clock\n");
41: err = -ENOENT;42: goto exit_error;
43: } 44: 45: s3c2410_nand_clk_set_state(info, CLOCK_ENABLE); 46: 47: /* allocate and map the resource */
48: 49: /* currently we assume we have the one resource */
50: res = pdev->resource; 51: size = resource_size(res); 52: 53: info->device = &pdev->dev; 54: info->platform = plat; 55: info->cpu_type = cpu_type; 56: 57: info->regs = devm_ioremap_resource(&pdev->dev, res);58: if (IS_ERR(info->regs)) {
59: err = PTR_ERR(info->regs);60: goto exit_error;
61: } 62: 63: dev_dbg(&pdev->dev, "mapped registers at %p\n", info->regs);
64: 65: /* initialise the hardware */
66: 67: err = s3c2410_nand_inithw(info);68: if (err != 0)
69: goto exit_error;
70: 71: sets = (plat != NULL) ? plat->sets : NULL; 72: nr_sets = (plat != NULL) ? plat->nr_sets : 1; 73: 74: info->mtd_count = nr_sets; 75: 76: /* allocate our information */
77: 78: size = nr_sets * sizeof(*info->mtds);
79: info->mtds = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);80: if (info->mtds == NULL) {
81: err = -ENOMEM;82: goto exit_error;
83: } 84: 85: /* initialise all possible chips */
86: 87: nmtd = info->mtds; 88: 89: for (setno = 0; setno < nr_sets; setno++, nmtd++) {
90: pr_debug("initialising set %d (%p, info %p)\n",
91: setno, nmtd, info); 92: 93: s3c2410_nand_init_chip(info, nmtd, sets); 94: 95: nmtd->scan_res = nand_scan_ident(&nmtd->mtd, 96: (sets) ? sets->nr_chips : 1, 97: NULL); 98: 99: if (nmtd->scan_res == 0) {
100: s3c2410_nand_update_chip(info, nmtd); 101: nand_scan_tail(&nmtd->mtd); 102: s3c2410_nand_add_partition(info, nmtd, sets); 103: } 104: 105: if (sets != NULL)
106: sets++; 107: } 108: 109: err = s3c2410_nand_cpufreq_register(info);110: if (err < 0) {
111: dev_err(&pdev->dev, "failed to init cpufreq support\n");
112: goto exit_error;
113: } 114: 115: if (allow_clk_suspend(info)) {
116: dev_info(&pdev->dev, "clock idle support enabled\n");
117: s3c2410_nand_clk_set_state(info, CLOCK_SUSPEND); 118: } 119: 120: pr_debug("initialised ok\n");
121: return 0;
122: 123: exit_error: 124: s3c24xx_nand_remove(pdev); 125: 126: if (err == 0)
127: err = -EINVAL;128: return err;
129: }第10行，获得tq2440_nand_info,其实是它的副本；
第21行，cpu_type是TYPE_S3C2410；
第38行，获得nand控制器的时钟；
第45行，使能nand控制器的时钟；
第67行，初始化nand控制器；
第72行，nr_sets的值是1；
第93行，根据cpu_type的设置初始化一些函数指针，如读函数、写函数以及片选函数；
第95行，读取NandFlash的ID，以及容量、规格（如pagesize），成功返回0；
第100行，设置一些关于ecc的信息；
第101行，设置一些关于oob读写的信息；
下面重点分析第102行的函数：s3c2410_nand_add_partition
1: static int s3c2410_nand_add_partition(struct s3c2410_nand_info *info,
2: struct s3c2410_nand_mtd *mtd,
3: struct s3c2410_nand_set *set)
4: {5: if (set) {
6: mtd->mtd.name = set->name; 7: 8: return mtd_device_parse_register(&mtd->mtd, NULL, NULL,
9: set->partitions, set->nr_partitions); 10: } 11: 12: return -ENODEV;
13: }第6行的set->name就是”Nand”
第9行的set->partitions中存放的是分区表，set->nr_partitions存放的是这个分区表的包含的分区个数
1: int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
2: struct mtd_part_parser_data *parser_data,
3: const struct mtd_partition *parts,
4: int nr_parts)
5: {6: int err;
7: struct mtd_partition *real_parts;
8: 9: err = parse_mtd_partitions(mtd, types, &real_parts, parser_data);10: if (err <= 0 && nr_parts && parts) {
11: real_parts = kmemdup(parts, sizeof(*parts) * nr_parts,
12: GFP_KERNEL);13: if (!real_parts)
14: err = -ENOMEM;15: else
16: err = nr_parts; 17: } 18: 19: if (err > 0) {
20: err = add_mtd_partitions(mtd, real_parts, err); 21: kfree(real_parts);22: } else if (err == 0) {
23: err = add_mtd_device(mtd);24: if (err == 1)
25: err = -ENODEV; 26: } 27: 28: return err;
29: }第9行，parse_mtd_partitions用于解析命令行中设置的分区，如果命令行中没有设置mtdparts，那么返回0，如果设置了，并且解析没问题，那么返回大于零的数，否则返回小于零的数。
u-boot中添加mtdparts支持以及Linux的分区设置
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原文地址：http://www.cnblogs.com/pengdonglin137/p/4646269.html
