u-boot中fdt命令的使用

[u-boot: v2012.10]

[Author: Bo Shen ]

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。

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U-Boot> fdt
fdt - flattened device tree utility commands

Usage:
fdt addr [] - Set the fdt location to
fdt move - Copy the fdt to and make it active
fdt resize - Resize fdt to size + padding to 4k addr
fdt print [] - Recursive print starting at
fdt list [] - Print one level starting at
fdt set [] - Set [to ]
fdt mknode - Create a new node after
fdt rm [] - Delete the node or
fdt header - Display header info
fdt bootcpu - Set boot cpuid
fdt memory - Add/Update memory node
fdt rsvmem print - Show current mem reserves
fdt rsvmem add - Add a mem reserve
fdt rsvmem delete - Delete a mem reserves
fdt chosen [ ] - Add/update the /chosen branch in the tree
/ - initrd start/end addr
NOTE: Dereference aliases by omiting the leading '/', e.g. fdt print ethernet0.
U-Boot>

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2.2 使用fdt命令

把device tree blob (dtb)文件下载到内存里。

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U-Boot> tftpboot 0x71000000 bshen/test-ek.dtb

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设置fdt的地址

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U-Boot> fdt addr 0x71000000

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然后就可以使用其余的命令参数了

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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

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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)：

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U-Boot> fdt print /memory
memory {
device_type = "memory";
reg = <0x70000000 0x4000000>;
};

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