请问全志R329如何通过uboot修改设备树属性？
本回答来源全志R329如何通过uboot修改设备树属性？
有时候经常需要临时调整部份设备树的属性配置，例如sdc的频率，以太网的delay参数。如果每次都源码修改后编译烧写，比较费时，所以uboot提供了临时修改的方法。
注：uboot修改都是单次启动有效，重启无效。
uboot常用命令
fdt
=> fdt -h
fdt - flattened device tree utility commands
Usage:
fdt addr [-c] <addr> [<length>] - Set the [control] fdt location to <addr>
fdt apply <addr> - Apply overlay to the DT
fdt boardsetup - Do board-specific set up
fdt move <fdt> <newaddr> <length> - Copy the fdt to <addr> and make it active
fdt resize [<extrasize>] - Resize fdt to size + padding to 4k addr + some optional <extrasize> if needed
fdt print <path> [<prop>] - Recursive print starting at <path>
fdt list <path> [<prop>] - Print one level starting at <path>
fdt get value <var> <path> <prop> - Get <property> and store in <var>
fdt get name <var> <path> <index> - Get name of node <index> and store in <var>
fdt get addr <var> <path> <prop> - Get start address of <property> and store in <var>
fdt get size <var> <path> [<prop>] - Get size of [<property>] or num nodes and store in <var>
fdt set <path> <prop> [<val>] - Set <property> [to <val>]
fdt mknode <path> <node> - Create a new node after <path>
fdt rm <path> [<prop>] - Delete the node or <property>
fdt header - Display header info
fdt bootcpu <id> - Set boot cpuid
fdt memory <addr> <size> - Add/Update memory node
fdt rsvmem print - Show current mem reserves
fdt rsvmem add <addr> <size> - Add a mem reserve
fdt rsvmem delete <index> - Delete a mem reserves
fdt chosen [<start> <end>] - Add/update the /chosen branch in the tree
<start>/<end> - initrd start/end addr
