1 Managing the device tree data in U-Boot
2 =======================================
4 The 'fdt' command can be used to manipulate the device tree (DT) data
5 that is passed from U-Boot to Linux.
7 - 'fdt boardsetup' will trim out some device nodes according to
10 Environment setting removed nodes
12 otg_mode=device usbotg
13 otg_mode=<UNSET> <both of the above> + usbphy
15 touchpanel=edt-ft5x06 ti,tsc2007
16 touchpanel=tsc2007 edt,edt-ft5x06
17 touchpanel=<UNSET> <both of the above>
19 Note: This command is automatically executed when booting Linux via
20 the 'bootm_cmd' environment variable.
22 - 'fdt rm' and 'fdt add' can be used to remove/create additional nodes
24 The whole DT data can be saved to and reloaded from the 'dtb' (or any
27 nand write.jffs2 ${fdtcontroladdr} dtb
29 Note: To prevent U-Boot from overwriting data in the succeeding
30 partition when encountering bad blocks in the 'dtb' partition, it is
31 wise to explicitly specify the write size according to 'totalsize'
32 displayed by the command 'fdt header':
33 TX53 U-Boot > fdt header
35 totalsize: 0x3f9e (16286)
37 off_dt_strings: 0x2bb8
42 size_dt_strings: 0x3e6
43 size_dt_struct: 0x2b40
45 TX53 U-Boot > nand write.jffs2 ${fdtcontroladdr} dtb 3f9e
47 If a DT is loaded from flash which should not be further manipulated
48 upon booting Linux, the string 'fdt boardsetup;' should be removed
49 from the 'bootm_cmd' environment variable.
52 nand read ${fdtcontroladdr} dtb