uboot中fdt命令的使用
转载：https://blog.csdn.net/voice_shen/article/details/7441894
依linux community的要求，从linux-3.5后，新提交的code必须对device tree进行支持。下面介绍如何使u-boot支持device tree，以及fdt命令的使用。
1. u-boot对fdt(flattened device tree)的支持。
实现：只要加入
#define CONFIG_OF_LIBFDT /* Device Tree support */
重新编译u-boot，就可以实现对device tree的支持。
2. u-boot下的fdt命令使用
2.1 首先查看fdt的帮助信息。
U-Boot> fdt fdt - flattened device tree utility commands Usage: fdt addr <addr> [<length>] - Set the fdt location to <addr> fdt move <fdt> <newaddr> <length> - Copy the fdt to <addr> and make it active fdt resize - Resize fdt to size + padding to 4k addr fdt print <path> [<prop>] - Recursive print starting at <path> fdt list <path> [<prop>] - Print one level starting at <path> 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 NOTE: Dereference aliases by omiting the leading '/', e.g. fdt print ethernet0. U-Boot>
2.2 使用fdt命令
把device tree blob (dtb)文件下载到内存里。
U-Boot> tftpboot 0x71000000 bshen/test-ek.dtb
设置fdt的地址
U-Boot> fdt addr 0x71000000
然后就可以使用其余的命令参数了
U-Boot> fdt header magic: 0xd00dfeed totalsize: 0x1887 (6279) off_dt_struct: 0x38 off_dt_strings: 0x1648 off_mem_rsvmap: 0x28 version: 17 last_comp_version: 16 boot_cpuid_phys: 0x0 size_dt_strings: 0x23f size_dt_struct: 0x1610 number mem_rsv: 0x0
fdt print 不跟参数时，打印出整颗树
fdt print加path参数，则打path内容，如下(其中/memory是path)：
U-Boot> fdt print /memory
memory {
device_type = "memory";
reg = <0x70000000 0x4000000>;
};