学习总结
此时Linux系统已经完毕,此时的启动方式,U-boot从内存卡启动,然后通过bootcmd命令配合bootargs参数引导U-boot从网络服务器(Ubuntu)指定位置通过TFTP协议将Linux镜像文件、设备树文件和根文件系统下载到EMMC中对应的三个分区中,然后在从EMMC中启动Linux内核
遇到的问题以及解决方法
网络频繁掉线
ALSA device list:
#0: wm8960-audio
VFS: Mounted root (nfs filesystem) on device 0:14.
devtmpfs: mounted
Freeing unused kernel memory: 440K (80b18000 - 80b86000)
vddsoc: unsupportable voltage range: 11750000-1450000uV
vddsoc: unsupportable voltage range: 11750000-1450000uV
cpu cpu0: failed to scale vddsoc up: -22
cpufreq: __target_index: Failed to change cpu frequency: -22
vddsoc: unsupportable voltage range: 11750000-1450000uV
vddsoc: unsupportable voltage range: 11750000-1450000uV
cpu cpu0: failed to scale vddsoc up: -22
cpufreq: __target_index: Failed to change cpu frequency: -22
can't run '/etc/init.d/rcS': No such file or directory
Please press Enter to activate this console.
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
random: nonblocking pool is initialized
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
fec 20b4000.ethernet eth0: Link is Down
fec 20b4000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
解决方法:将 LCD 的电气属性都设置为 0X79,这里将其都改为 0X49,也就是将 LCD 相关 IO 的驱动能力改为 R0/1,也就是降低 LCD 相关 IO 的驱动能力。因为前面已经说了,正点原子的 ALPHA 开发板上的 LCD 接口用了三个 SGM3157 模拟开关,为了防止模拟开关影响到网络,因此这里需要降低 LCD 数据线的驱动能力,如果你所使用的板子没有用到模拟开关那么就不需要将 0X79 改为 0X49。
详见 《Linux驱动开发指南V1.5.2》P1394
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