android2.3.4----8. nand flash驱动分析

原文地址：http://blog.chinaunix.net/uid-26009923-id-4140652.html

一． nand devices分析
1.1 platform_devices的添加
在arch/arm/plat-samsun/dev-nand.c中

static struct resource s3c_nand_resource[] = {
    [0] = {
        .start = S3C_PA_NAND,
        .end = S3C_PA_NAND + SZ_1M,
        .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,
};
EXPORT_SYMBOL(s3c_device_nand);

别看这儿是s3c2410-nand后来又设置为s3c6410-nand
arch/arm/mach-s3c64xx/s3c6410.c中

void __init s3c6410_map_io(void)
{
    s3c_device_nand.name = "s3c6410-nand";
}

1.1 分区信息的添加
在arch/arm/mach-s3c64xx/mach-smdk6410.c中

struct mtd_partition ok6410_nand_part[] = {
    {
        .name        = "Bootloader",
        .offset        = 0,
        .size        = (1 * SZ_1M),
        .mask_flags    = MTD_CAP_NANDFLASH,
    },
    {
        .name        = "Kernel",
        .offset        = (1 * SZ_1M),
        .size        = (5*SZ_1M) ,
        .mask_flags    = MTD_CAP_NANDFLASH,
    },

    {
        .name        = "User",
        .offset        = (6 * SZ_1M),
        .size        = (200*SZ_1M) ,
    },
    {
        .name        = "File System",
        .offset        = MTDPART_OFS_APPEND,
        .size        = MTDPART_SIZ_FULL,
    }
};

static struct s3c2410_nand_set ok6410_nand_sets[] = {
    [0] = {
        .name = "nand",
        .nr_chips = 1,
        .nr_partitions = ARRAY_SIZE(ok6410_nand_part),
        .partitions = ok6410_nand_part,
    },
};

static struct s3c2410_platform_nand ok6410_nand_info = {
    .tacls = 25,
    .twrph0 = 55,
    .twrph1 = 40,
    .nr_sets = ARRAY_SIZE(ok6410_nand_sets),
    .sets = ok6410_nand_sets,
};

然后在smdk6410_machine_init中添加
    s3c_nand_set_platdata(&ok6410_nand_info);

void __init s3c_nand_set_platdata(struct s3c2410_platform_nand *nand)
{
    s3c_device_nand.dev.platform_data = nand;
}

二. nand driver分析
在drivers/mtd/nand/s3c_nand.c中
module_init(s3c_nand_init);
--> s3c_nand_init

static int __init s3c_nand_init(void)
{
    printk("S3C NAND Driver, (c) 2008 Samsung Electronics\n");
    return platform_driver_register(&s3c6410_nand_driver);
}

匹配name

static struct platform_driver s3c6410_nand_driver = {
    .probe        = s3c6410_nand_probe,
    .remove        = s3c_nand_remove,
    .suspend    = s3c_nand_suspend,
    .resume        = s3c_nand_resume,
    .driver        = {
        .name    = "s3c6410-nand",
        .owner    = THIS_MODULE,
    },
};

进入probe函数

static int s3c6410_nand_probe(struct platform_device *dev)
{
    return s3c_nand_probe(dev, TYPE_S3C6410);
}

再次进入调用

static int s3c_nand_probe(struct platform_device *pdev, enum s3c_cpu_type cpu_type)
{
    struct s3c2410_platform_nand *plat = pdev->dev.platform_data;
    struct s3c2410_nand_set *sets;
    struct nand_chip *nand;
    struct resource *res;

    struct nand_flash_dev *type = NULL;
    //打开nand flash 时钟
    s3c_nand.clk = clk_get(&pdev->dev, "nand");
    clk_enable(s3c_nand.clk);
    //ioremap  Nand flash控制寄存器
    res = pdev->resource;
    size = res->end - res->start + 1;
    s3c_nand.area = request_mem_region(res->start, size, pdev->name);
    s3c_nand.cpu_type = cpu_type;
    s3c_nand.device = &pdev->dev;
    s3c_nand.regs = ioremap(res->start, size);
    s3c_nand.platform = plat;

    sets = (plat != NULL) ? plat->sets : NULL;      //sets.partitions就是分区信息
    nr_sets = (plat != NULL) ? plat->nr_sets : 1;   //nr_sets=1

    s3c_nand.mtd_count = nr_sets;

    //分配内存大小为: mtd_info + nand_chip,并初始化
    s3c_mtd = kmalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip), GFP_KERNEL);
    nand = (struct nand_chip *) (&s3c_mtd[1]);  //所以nand_chip的起始地址是&mtd_info[1]
    memset((char *) s3c_mtd, 0, sizeof(struct mtd_info));
    memset((char *) nand, 0, sizeof(struct nand_chip));

    s3c_mtd->priv = nand;

    for (i = 0; i < sets->nr_chips; i++) {                 //sets->nr_chips=1
        nand->IO_ADDR_R      = (char *)(s3c_nand.regs + S3C_NFDATA);
        nand->IO_ADDR_W      = (char *)(s3c_nand.regs + S3C_NFDATA);
        nand->cmd_ctrl       = s3c_nand_hwcontrol;
        nand->dev_ready      = s3c_nand_device_ready;
        nand->scan_bbt       = s3c_nand_scan_bbt;
        nand->options        = 0;
        nand->ecc.mode       = NAND_ECC_HW;
        nand->ecc.hwctl      = s3c_nand_enable_hwecc;
        nand->ecc.calculate  = s3c_nand_calculate_ecc;
        nand->ecc.correct    = s3c_nand_correct_data;
        //发起读取设备ID流程
        s3c_nand_hwcontrol(0, NAND_CMD_READID, NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
        s3c_nand_hwcontrol(0, 0x00, NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE);
        s3c_nand_hwcontrol(0, 0x00, NAND_NCE | NAND_ALE);
        s3c_nand_hwcontrol(0, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
        s3c_nand_device_ready(0);
            //第1次读取的是device code=0xD5
        tmp = readb(nand->IO_ADDR_R);
        dev_id = tmp = readb(nand->IO_ADDR_R);
            //查表获取 nand flash的硬件信息
          // name                     id    pagesize chipsize    erasesize       option            
          // {"NAND 2GiB 3,3V 8-bit", 0xD5, 4096,    2048,       512*1024,   LP_OPTIONS},
        for (j = 0; nand_flash_ids[j].name != NULL; j++) {
            if (tmp == nand_flash_ids[j].id) {
                type = &nand_flash_ids[j];
                break;
            }
        }

        nand->cellinfo = readb(nand->IO_ADDR_R);
        tmp = readb(nand->IO_ADDR_R);
        if (!type->pagesize) {
            if (((nand->cellinfo >> 2) & 0x3) == 0) {
            } else {
                nand_type = S3C_NAND_TYPE_MLC_4BIT;
                nand->options |= NAND_NO_SUBPAGE_WRITE;
                nand->ecc.read_page = s3c_nand_read_page_4bit;
                nand->ecc.write_page = s3c_nand_write_page_4bit;
                nand->ecc.size = 512;
                nand->ecc.bytes = 8;
                nand->ecc.layout = &s3c_nand_oob_mlc_64;
                if(dev_id == 0xd5)
                {
                    printk("dev_id == 0xd5 select s3c_nand_oob_mlc_128\n");
                    nand_type = S3C_NAND_TYPE_MLC_8BIT;
                    nand->ecc.read_page = s3c_nand_read_page_8bit;
                    nand->ecc.write_page = s3c_nand_write_page_8bit;
                    nand->ecc.size = 512;
                    nand->ecc.bytes = 13;
                    nand->ecc.layout = &s3c_nand_oob_mlc_128_8bit;
                }
            }
        }
        nand_scan(s3c_mtd, 1);
        add_mtd_partitions(s3c_mtd, sets->partitions, sets->nr_partitions);
    }
    return 0;
}

nand_scan
    -->nand_scan_ident
            --> nand_set_defaults         设置chip的指针
            --> nand_get_flash_type     获取flash的类型
nand_scan
    --> nand_scan_tail                      设置chip->ecc的指针 及 mtd的一些指针
            --> chip->scan_bbt              最后调用scan_bbt,不过这儿直接返回0

int add_mtd_partitions(struct mtd_info *master, const struct mtd_partition *parts, int nbparts)
{
    struct mtd_part *slave;
    uint64_t cur_offset = 0;
    for (i = 0; i < nbparts; i++) {
        slave = add_one_partition(master, parts + i, i, cur_offset);
        cur_offset = slave->offset + slave->mtd.size;
    }

    return 0;
}
EXPORT_SYMBOL(add_mtd_partitions);