手头上有飞凌的OK6410开发板，想通过sd uboot 启动linux和yaffs根文件系统，考虑过几种实现方式
1. 通过S3C6410的sd启动功能，把带下载功能的uboot烧录到sd卡的启动扇区中，当uboot启动时，通过它的网络下载或者usb下载功能把linux内核下载到内存中，再把根文件系统下载并烧录到nand flash中，接着启动内核从而启动整个系统。
2. 通过S3C6410的sd启动功能，把带下载功能以及文件系统读取功能的uboot烧录到sd卡的启动扇区，当uboot启动时，把放入sd卡的uboot、linux内核和文件系统写入nand flash中，再转成用nand flash 启动，然后启动linux系统。
3. 通过S3C6410的sd启动功能，把带下载功能的uboot烧录到sd卡的启动扇区中，再把linux内核也写入sd卡的对应扇区中，接着通过usb或者网络下载功能把yaffs文件系统下载到nand flash中，接着就从sd卡直接启动linux系统。
这里只使用了方法3，但也由于某些问题，还借助了飞凌的一键烧录的方式来烧录yaffs2文件系统到nand flash中。
使用三星的sd uboot源码，对sd uboot进行修改：
a. 在include目录中的configs的S3C6410.h文件中，打开sd boot的选项如下图。
b．增加sd卡的copy功能并设置正确的zImage的读取位置：把下面的PART_ROOTFS_OFFSET改成0X400000 ,因为我使用的是飞凌的linux内核，大小已经超过3M，所以就指定为4M。
把下面的ofsinfo.zimage改成1973148672/512,注意这个位置也是zImage写入sd卡的位置。
c． 增加nand flash的功能，参考《uboot支持NAND部分代码》这个目录里面的文件，或者飞凌的uboot的源代码中的nand flash部分的内容。
d．增加网络的功能，直接参考移植后的dm9000x文件就可以了，但注意在smdk6410.h文件中增加如下的宏：
//added for achieving the OK6410 netfunction
#define CONFIG_DRIVER_DM9000 1
#define CONFIG_DM9000_BASE 0x18000000
#define DM9000_IO CONFIG_DM9000_BASE
#define DM9000_DATA (CONFIG_DM9000_BASE+4)
#define CONFIG_DM9000_USE_16BIT
e．增加usb的功能，其实usb的功能只要把usbd-otg-hs.c文件按如下修改：
f．设置bootargs如下：
setenv bootargs "init=/linuxrcroot=/dev/mtdblock2 rootfstype=yaffs2 console=ttySAC0,115200"
g. 注意nandflash的分区如下：
0x000000000000-0x000000100000: "Bootloader"
0x000000100000-0x000000600000: "Kernel"
0x000000600000-0x000080000000 : "FileSystem"
h．sd卡上如何烧写内核和sd uboot请参考《SD&SDHC下载UBOOT注意事项》和《WINHEX的使用手册》。
i. zImage 和yaffs文件系统使用飞凌现成的文件rootfs.yaffs2-nand2g和zImage,请查看此文件夹中的该文件。
j.如果使用USB下载的话，还需要在主机端装USB的驱动，请查看此文件夹的USB驱动并按照到你的主机上。
k.nand flash的读取命令和写命令有时候会执行不了，可以多写几遍。另外，在写之前好像一定要擦除。
注意：
1. 不管是用USB还是用TFTP功能，下载rootfs.yaffs2-nand2g文件的时候都会下载到90%左右死机，因此，我还是借助了一键安装的功能先把文件系统写到nand flash中的。否则目前还没有办法把 yaffs文件系统放到NAND FLASH的指定分区中。
2.另外，我使用的是sandisk 2G的 sd卡，其他的sd卡我没有试过，但sdhc卡一定是不行的，因为sd uboot里面的驱动只针对sd卡。下载镜像到sd卡我使用的工具是WINHEX软件（记得要用破解版，否则无法写入）。
下面贴上串口输出的整个启动过程：
U-Boot 1.1.6 (Sep 17 2012 - 18:32:43) for SMDK6410
CPU: S3C6410@532MHz
Fclk =532MHz, Hclk = 133MHz, Pclk = 66MHz, Serial = CLKUART (SYNC Mode)
Board: SMDK6410
DRAM: 128 MB
Flash: 0 kB
NAND: 2048 MB
SanDisk MMC: => rca=0x0000e624
1887 MB
In: serial
Out: serial
Err: serial
Hit any key to stop autoboot: 0
Reading zImage from block 3853806.. Completed!
Boot with zImage
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
Linux version 3.0.1 (root@forlinx) (gcc version 4.3.2(Sourcery G++ Lite 2008q3-72) ) #425 Mon May 7 16:56:20 CST 2012
S3C24XX Clocks, Copyright 2004 Simtec Electronics
camera: no parent clock specified
S3C64XX: PLL settings, A=532000000, M=532000000,E=24000000
S3C64XX: HCLK2=266000000, HCLK=133000000,PCLK=66500000
mout_apll: source is fout_apll (1), rate is 532000000
mout_epll: source is epll (1), rate is 24000000
mout_mpll: source is mpll (1), rate is 532000000
mmc_bus: source is mout_epll (0), rate is 24000000
mmc_bus: source is mout_epll (0), rate is 24000000
mmc_bus: source is mout_epll (0), rate is 24000000
usb-bus-host: source is clk_48m (0), rate is 48000000
uclk1: source is dout_mpll (1), rate is 66500000
spi-bus: source is mout_epll (0), rate is 24000000
spi-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
audio-bus: source is mout_epll (0), rate is 24000000
irda-bus: source is mout_epll (0), rate is 24000000
camera: no parent clock specified
Kernel command line: init=/linuxrc root=/dev/mtdblock2rootfstype=yaffs2 console=ttySAC0,115200
PID hash table entries: 512 (order: -1, 2048 bytes)
Dentry cache hash table entries: 16384 (order: 4,65536 bytes)
Inode-cache hash table entries: 8192 (order: 3, 32768bytes)
Memory: 128MB = 128MB total
Memory: 67672k/67672k available, 63400k reserved, 0Khighmem
Virtual kernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
DMA : 0xff600000 - 0xffe00000 ( 8MB)
vmalloc :0xc8800000 - 0xf4000000 ( 696 MB)
lowmem : 0xc0000000 - 0xc8000000 ( 128 MB)
pkmap : 0xbfe00000 - 0xc0000000 ( 2MB)
modules :0xbf000000 - 0xbfe00000 ( 14 MB)
.init : 0xc0008000- 0xc0034000 ( 176 kB)
.text :0xc0034000 - 0xc0701080 (6965 kB)
.data :0xc0702000 - 0xc0744330 ( 265 kB)
.bss :0xc0744354 - 0xc07c1ce0 ( 503 kB)
SLUB: Genslabs=13, HWalign=32, Order=0-3,MinObjects=0, CPUs=1, Nodes=1
NR_IRQS:246 nr_irqs:246 246
VIC @f4000000: id 0x00041192, vendor 0x41
VIC @f4010000: id 0x00041192, vendor 0x41
Console: colour dummy device 80x30
console [ttySAC0] enabled
Calibrating delay loop... 528.79 BogoMIPS(lpj=2643968)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
hw perfevents: enabled with v6 PMU driver, 3 countersavailable
devtmpfs: initialized
NET: Registered protocol family 16
hw-breakpoint: found 6 breakpoint and 1 watchpointregisters.
hw-breakpoint: maximum watchpoint size is 4 bytes.
s3c64xx_dma_init: Registering DMA channels
PL080: IRQ 73, at c8804000, channels 0..8
PL080: IRQ 74, at c8806000, channels 8..16
bio: create slab <bio-0> at 0
SCSI subsystem initialized
------------[ cut here ]------------
WARNING: at drivers/gpio/gpiolib.c:101gpio_ensure_requested+0x58/0x124()
---[ end trace da227214a82491b7 ]---
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
s3c-i2c s3c2440-i2c.0: slave address 0x10
s3c-i2c s3c2440-i2c.0: bus frequency set to 64 KHz
s3c-i2c s3c2440-i2c.0: i2c-0: S3C I2C adapter
Advanced Linux Sound Architecture Driver Version1.0.23.
cfg80211: Calling CRDA to update world regulatorydomain
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0,4096 bytes)
TCP established hash table entries: 4096 (order: 3,32768 bytes)
TCP bind hash table entries: 4096 (order: 2, 16384bytes)
TCP: Hash tables configured (established 4096 bind4096)
TCP reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transportmodule.
audit: initializing netlink socket (disabled)
type=2000 audit(0.270:1): initialized
msgmni has been set to 132
alg: No test for stdrng (krng)
Block layer SCSI generic (bsg) driver version 0.4loaded (major 253)
io scheduler noop registered
io scheduler deadline registered
io scheduler cfq registered (default)
LCD TYPE :: LTE480WV will be initialized
Console: switching to colour frame buffer device 60x34
fb0: s3cfb frame buffer device
fb1: s3cfb frame buffer device
fb2: s3cfb frame buffer device
fb3: s3cfb frame buffer device
s3c6400-uart.0: ttySAC0 at MMIO 0x7f005000 (irq = 16)is a S3C6400/10
s3c6400-uart.1: ttySAC1 at MMIO 0x7f005400 (irq = 20)is a S3C6400/10
s3c6400-uart.2: ttySAC2 at MMIO 0x7f005800 (irq = 24)is a S3C6400/10
s3c6400-uart.3: ttySAC3 at MMIO 0x7f005c00 (irq = 28)is a S3C6400/10
Hello, world
NAND device: Manufacturer ID: 0xec, Chip ID: 0xd5(Samsung NAND 2GiB 3,3V 8-bit)
Creating 3 MTD partitions on "NAND 2GiB 3,3V8-bit":
0x000000000000-0x000000100000 : "Bootloader"
0x000000100000-0x000000600000 : "Kernel"
0x000000600000-0x000080000000 : "FileSystem"
vcan: Virtual CAN interface driver
slcan: serial line CAN interface driver
slcan: 10 dynamic interface channels.
CAN device driver interface
mcp251x: setup gpio pins CS and External Int
mcp2515 spi1.0: MCP251x didn't enter in conf modeafter reset
mcp2515 spi1.0: Probe failed
mcp2515 spi1.0: probe failed
PPP generic driver version 2.4.2
PPP Deflate Compression module registered
PPP BSD Compression module registered
PPP MPPE Compression module registered
NET: Registered protocol family 24
dm9000 Ethernet Driver, V1.31
eth0: dm9000a at c881c000,c8c00004 IRQ 108 MAC:08:90:00:a0:90:90 (platform data)
libertas_sdio: Libertas SDIO driver
libertas_sdio: Copyright Pierre Ossman
usbcore: registered new interface driver rt73usb
ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
s3c2410-ohci s3c2410-ohci: S3C24XX OHCI
s3c2410-ohci s3c2410-ohci: new USB bus registered,assigned bus number 1
s3c2410-ohci s3c2410-ohci: irq 79, io mem 0x74300000
usb usb1: New USB device found, idVendor=1d6b,idProduct=0001
usb usb1: New USB device strings: Mfr=3, Product=2,SerialNumber=1
usb usb1: Product: S3C24XX OHCI
usb usb1: Manufacturer: Linux 3.0.1 ohci_hcd
usb usb1: SerialNumber: s3c24xx
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
usbcore: registered new interface driver cdc_acm
cdc_acm: USB Abstract Control Model driver for USBmodems and ISDN adapters
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usbcore: registered new interface driver usbserial
USB Serial support registered for generic
usbcore: registered new interface driverusbserial_generic
usbserial: USB Serial Driver core
USB Serial support registered for GSM modem (1-port)
usbcore: registered new interface driver option
option: v0.7.2:USB Driver for GSM modems
USB Serial support registered for pl2303
usbcore: registered new interface driver pl2303
pl2303: Prolific PL2303 USB to serial adaptor driver
dummy_hcd dummy_hcd: USB Host+Gadget Emulator, driver02 May 2005
dummy_hcd dummy_hcd: Dummy host controller
dummy_hcd dummy_hcd: new USB bus registered, assignedbus number 2
usb usb2: New USB device found, idVendor=1d6b,idProduct=0002
usb usb2: New USB device strings: Mfr=3, Product=2,SerialNumber=1
usb usb2: Product: Dummy host controller
usb usb2: Manufacturer: Linux 3.0.1 dummy_hcd
usb usb2: SerialNumber: dummy_hcd
hub 2-0:1.0: USB hub found
hub 2-0:1.0: 1 port detected
mousedev: PS/2 mouse device common for all mice
input: gpio-keys as/devices/platform/gpio-keys/input/input0
input: s3c-keypad as/devices/platform/s3c-keypad/input/input1
S3C Touchscreen driver, (c) 2008 Samsung Electronics
S3C TouchScreen got loaded successfully : 12 bits
input: S3C TouchScreen as/devices/virtual/input/input2
s3c-rtc s3c64xx-rtc: rtc disabled, re-enabling
s3c-rtc s3c64xx-rtc: rtc core: registered s3c as rtc0
i2c /dev entries driver
Linux video capture interface: v2.00
gspca: main v2.10.0 registered
usbcore: registered new interface driver benq
benq: registered
usbcore: registered new interface driver conex
conex: registered
usbcore: registered new interface driver cpia1
cpia1: registered
usbcore: registered new interface driver etoms
etoms: registered
usbcore: registered new interface driver finepix
finepix: registered
usbcore: registered new interface driver jeilinj
jeilinj: registered
usbcore: registered new interface driver mars
mars: registered
usbcore: registered new interface driver mr97310a
mr97310a: registered
usbcore: registered new interface driver ov519
ov519: registered
usbcore: registered new interface driver ov534
ov534: registered
usbcore: registered new interface driver ov534_9
ov534_9: registered
usbcore: registered new interface driver pac207
pac207: registered
usbcore: registered new interface driver pac7302
pac7302: registered
usbcore: registered new interface driver pac7311
pac7311: registered
usbcore: registered new interface driver sn9c2028
sn9c2028: registered
usbcore: registered new interface driver sn9c20x
sn9c20x: registered
usbcore: registered new interface driver sonixb
sonixb: registered
usbcore: registered new interface driver sonixj
sonixj: registered
usbcore: registered new interface driver spca500
spca500: registered
usbcore: registered new interface driver spca501
spca501: registered
usbcore: registered new interface driver spca505
spca505: registered
usbcore: registered new interface driver spca506
spca506: registered
usbcore: registered new interface driver spca508
spca508: registered
usbcore: registered new interface driver spca561
spca561: registered
usbcore: registered new interface driver spca1528
spca1528: registered
usbcore: registered new interface driver sq905
sq905: registered
usbcore: registered new interface driver sq905c
sq905c: registered
usbcore: registered new interface driver sq930x
sq930x: registered
usbcore: registered new interface driver sunplus
sunplus: registered
usbcore: registered new interface driver stk014
stk014: registered
usbcore: registered new interface driver stv0680
stv0680: registered
usbcore: registered new interface driver t613
t613: registered
usbcore: registered new interface driver tv8532
tv8532: registered
usbcore: registered new interface driver vc032x
vc032x: registered
usbcore: registered new interface driver zc3xx
zc3xx: registered
usbcore: registered new interface driver ALi m5602
ALi m5602: registered
usbcore: registered new interface driver STV06xx
STV06xx: registered
gspca_gl860: driver startup - version 0.9d10
usbcore: registered new interface driver gspca_gl860
gspca_gl860: driver registered
s3c-fimc: controller 0 registered successfully
s3c-fimc: controller 1 registered successfully
s3c-fimc: info ov965x_init
cym s3c_mfc_mememap: addr:55af9000 size:1138688
S3C6400 MFC Driver, (c) 2007 Samsung Electronics
S3C PostProcessor Driver v3.12, (c) 2009 SamsungElectronics
S3C6410 TV encoder Driver, (c) 2008 SamsungElectronics
S3C6410 TV scaler Driver, (c) 2008 Samsung Electronics
S3C Rotator Driver, (c) 2008 Samsung Electronics
s3c_rotator_probe called
S3C JPEG Driver, (c) 2007 Samsung Electronics
s3c_g2d_probe called
s3c_g2d_probeSuccess
S3C G3D Driver, (c) 2007-2009 Samsung Electronics
S3C CMM Driver, (c) 2008 Samsung Electronics
usbcore: registered new interface driver uvcvideo
USB Video Class driver (v0.1.0)
S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics
s3c2410-wdt s3c2410-wdt: watchdog inactive, resetdisabled, irq enabled
sdhci: Secure Digital Host Controller Interface driver
sdhci: Copyright(c) Pierre Ossman
s3c-sdhci s3c-sdhci.0: clock source 0: hsmmc(133000000 Hz)
s3c-sdhci s3c-sdhci.0: clock source 1: hsmmc (133000000Hz)
s3c-sdhci s3c-sdhci.0: clock source 2: mmc_bus(24000000 Hz)
mmc0: SDHCI controller on samsung-hsmmc [s3c-sdhci.0]using ADMA
s3c-sdhci s3c-sdhci.1: clock source 0: hsmmc(133000000 Hz)
s3c-sdhci s3c-sdhci.1: clock source 1: hsmmc(133000000 Hz)
s3c-sdhci s3c-sdhci.1: clock source 2: mmc_bus(24000000 Hz)
mmc1: SDHCI controller on samsung-hsmmc [s3c-sdhci.1]using ADMA
usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
mmc0: new SD card at address e624
mmcblk0: mmc0:e624 SU02G 1.84 GiB
mmcblk0: p1
asoc: wm9713-hifi <-> samsung-ac97 mapping ok
ALSA device list:
#0: smdk6410
TCP cubic registered
NET: Registered protocol family 17
can: controller area network core (rev 20090105 abi 8)
NET: Registered protocol family 29
can: raw protocol (rev 20090105)
can: broadcast manager protocol (rev 20090105 t)
lib80211: common routines for IEEE802.11 drivers
Registering the dns_resolver key type
s3c-rtc s3c64xx-rtc: setting system clock to2000-03-08 17:26:07 UTC (952536367)
yaffs: dev is 32505858 name is "mtdblock2"rw
yaffs: passed flags ""
VFS: Mounted root (yaffs2 filesystem) on device 31:2.
devtmpfs: mounted
Freeing init memory: 176K
FAT-fs (mmcblk0p1): utf8 is not a recommended IOcharset for FAT filesystems, filesystem will be case sensitive!
Try to bring eth0 interface up......dm9000 dm9000.0:eth0: link down
Done
Starting Qtopia2, please waiting...
Please press Enter to activate thisconsole. touch...