Hello Park Chan,
If set this restricts the maximum address that the flattened device tree will be copied into upon boot.
For example, if you have a system with 1 GB memory at physical address 0x10000000, while Linux kernel only recognizes the first 704 MB as low memory, you may need to set fdt_high as 0x3C000000 to have the device tree blob be copied to the maximum address of the 704 MB low memory, so that Linux kernel can access it during the boot procedure.
LS1021ATWR has 2G memory at physical address 0x80000000, and according to Linux Kernel memory map, 1G low memory is allocated for the system, so it seems that configure fdt_high at "0xbfffffff" should be more reasonable.
Have a great day,
Yiping
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