ROM的扫描顺序为：UART3-->SD card-->Nand Flash
在UART3时，可以使用Transfer --> XMODEM --> Send (1K mode)
分别传MLO.Byteswap和u-boot.img即可以在RAM运行
运行u-boot成功后，就要重新烧写MLO.Byteswap和u-boot.img两个文件到flash了。
1.SPI Flash大小
2M Bytes(0x00 000 ~ 0x1F FFFF)
[ 1.386505] 0x000000000000-0x000000020000 : "SPL"
[ 1.392761] 0x000000020000-0x00000007f000 : "U-Boot"
[ 1.406433] 0x00000007f000-0x000000080000 : "U-Boot Env"
2.u-boot对SPI的操作有
sf - SPI flash sub-system
Usage:
sf probe [[bus:]cs] [hz] [mode] - init flash device on given SPI bus
and chip select
sf read addr offset len - read `len' bytes starting at
`offset' to memory at `addr'
sf write addr offset len - write `len' bytes from memory
at `addr' to flash at `offset'
sf erase offset [+]len - erase `len' bytes from `offset'
`+len' round up `len' to block size
sf update addr offset len - erase and write `len' bytes from memory
at `addr' to flash at `offset'
3.通过SD卡启动，进入U-boot
U-Boot# sf probe 0
SF: Detected GD25Q16 with page size 4 KiB, total 2 MiB
U-Boot# sf erase 0 +200000
//sdcard=======================
U-Boot# mmc rescan
U-Boot# fatload mmc 0 ${loadaddr} MLO.byteswap
reading MLO.byteswap
101117 bytes read in 18 ms (5.4 MiB/s)
U-Boot# sf write ${loadaddr} 0 0x20000
U-Boot# fatload mmc 0 ${loadaddr} u-boot.img
reading u-boot.img
364768 bytes read in 45 ms (7.7 MiB/s)
U-Boot# sf write ${loadaddr} 0x20000 0x60000
* 0x00000 - 0x20000 : First copy of SPL
* 0x20000 - 0xE0000 : U-Boot
* 0xE0000 - 0x100000 : U-Boot Environment
* 0x100000 - 0x200000: Reserved
U-Boot# sf probe 0
SF: Detected GD25Q16 with page size 4 KiB, total 2 MiB
U-Boot# loady
## Ready for binary (ymodem) download to 0x80200000 at 115200 bps...
CCCCCCC
开始 ymodem 传输。 按 Ctrl+C 取消。
100% 98 KB 5 KB/s 00:00:18 0 Errors
xyzModem - CRC mode, 792(SOH)/0(STX)/0(CAN) packets, 9 retries
## Total Size = 0x00018afd = 101117 Bytes
U-Boot# sf erase 0 +200000
U-Boot# sf write 0x80200000 0 0x20000
U-Boot# loady
## Ready for binary (ymodem) download to 0x80200000 at 115200 bps...
CCCC
开始 ymodem 传输。 按 Ctrl+C 取消。
100% 355 KB 6 KB/s 00:00:54 0 Errors
xyzModem - CRC mode, 2849(SOH)/0(STX)/0(CAN) packets, 6 retries
## Total Size = 0x00058f40 = 364352 Bytes
U-Boot# sf erase 0x20000 0xc0000
U-Boot# sf write 0x80200000 0x20000 0xc0000
