Environment

  • Board: BPI-F3 (SpacemiT K1)
  • Prerequisite: TFTP server already running on the host machine

Setting Up IP Addresses

Find the host IP:

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ifconfig
# Look for the interface connected to the board
# e.g. inet 192.168.230.28

In U-Boot, set the board and server IPs:

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setenv ipaddr 192.168.230.4
setenv serverip 192.168.230.28
saveenv

Make sure both are on the same subnet.

Configuring PXE Files

On the host, set up the TFTP directory:

.
├── Image
├── k1-x_deb1.dtb
└── pxelinux.cfg
    └── 01-fe-fe-fe-81-b4-a8
  • Image — the Linux kernel image
  • k1-x_deb1.dtb — the device tree blob
  • pxelinux.cfg/ — directory containing PXE config files

Config File Naming

PXE looks up config files by a priority order based on U-Boot variables. The highest priority is the MAC address. Check it in U-Boot:

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printenv ethaddr
# ethaddr=FE:FE:FE:81:B4:A8

The config filename is the MAC address in lowercase, separated by hyphens, prefixed with 01- (the ARP hardware type for Ethernet):

01-fe-fe-fe-81-b4-a8

Config File Content

The format is identical to extlinux.conf:

default linux

label linux
	kernel Image
	fdt k1-x_deb1.dtb
	append earlycon=sbi earlyprintk console=ttyS0,115200 loglevel=8 clk_ignore_unused swiotlb=65536 rdinit=/init workqueue.default_affinity_scope=system root=/dev/mmcblk2p6 rootwait rootfstype=ext4

Booting

In U-Boot:

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pxe get
pxe boot

Pitfall: Missing fdt_addr_r

If the kernel hangs during boot, check the log for something like:

## Flattened Device Tree blob at 7deb2e10
   Booting using the fdt blob at 0x7deb2e10

This address (0x7deb2e10) is not where your DTB was loaded — it’s fdtcontroladdr, U-Boot’s own internal device tree. This means PXE didn’t know where to load the DTB you specified.

PXE loads the kernel to kernel_addr_r and the DTB to fdt_addr_r. On this board, kernel_addr_r was set but fdt_addr_r was not:

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printenv kernel_addr_r
# kernel_addr_r=0x11000000

printenv fdt_addr_r
# Error: "fdt_addr_r" not defined

The fix:

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setenv fdt_addr_r 0x31000000
saveenv

After this, pxe get && pxe boot works correctly — the DTB is loaded to the right address and the kernel boots with the proper device tree.

Reference