在基于 ARM Cortex A9 的 xilinx 芯片上启动 Linux 时，我不断收到此错误：
U-Boot 2013.07 (Mar 31 2014 - 16:34:50)
Memory: ECC disabled
DRAM: 1 GiB
MMC: zynq_sdhci: 0
SF: Detected N25Q128A with page size 64 KiB, total 16 MiB
*** Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
Net: Gem.e000b000
U-BOOT for Xilinx-ZC702-2013.3
Gem.e000b000 Waiting for PHY auto negotiation to complete......... TIMEOUT !
BOOTP broadcast 1
BOOTP broadcast 2
BOOTP broadcast 3
BOOTP broadcast 4
BOOTP broadcast 5
Retry count exceeded
Hit any key to stop autoboot: 0
SF: Detected N25Q128A with page size 64 KiB, total 16 MiB
SF: 11010048 bytes @ 0x520000 Read: OK
Wrong Image Format for bootm command
ERROR: can't get kernel image!
U-Boot-PetaLinux>
即使明确给出命令也不起作用：
U-Boot-PetaLinux> run sfboot
SF: Detected N25Q128A with page size 64 KiB, total 16 MiB
SF: 11010048 bytes @ 0x520000 Read: OK
Wrong Image Format for bootm command
ERROR: can't get kernel image!
U-Boot-PetaLinux>
我的环境变量：
U-Boot-PetaLinux> printenv bootcmd
bootcmd=setenv var "if test ${dtbsize} -le 0; then run sfboot; else run dtbboot; fi"; run var; setenv var
我使用的是 uImage，它是使用 mkimage 工具转换 zImage 后得到的。
知道图像格式有什么问题吗？