Ubuntu 20.04 PXE boot hangs on rockpi4a 1.4

I am trying to boot the Ubuntu Focal (rockpi4a_ubuntu_focal_server_arm64_20210125_2342-gpt.img) over network (TFTP + NFS) on the rockpi4a 1.4. I’ve followed the article wiki.radxa.com/Rockpi4/dev/u-boot/pxe but It seems there is some problem loading the rootfs from NFS server (see the log below).

  1. I am able to boot the kernel, but it hangs after disabling uart0 (bootconsole [uart0] disabled)
  2. I belive that the kernel should mount the root filesystem from NFS server as instructed by the bootargs. this is my pxelinux.cfg/default file:

label kernel-4.4.154-112-rockchip-gfdb18c8bab17
kernel /vmlinuz-4.4.154-112-rockchip-gfdb18c8bab17
initrd /initrd.img-4.4.154-112-rockchip-gfdb18c8bab17
devicetreedir /dtbs/4.4.154-112-rockchip-gfdb18c8bab17
append earlycon=uart8250,mmio32,0xff1a0000 earlyprintk console=ttyS2,1500000n8 init=/sbin/init netboot=nfs root=/dev/nfs rootfstype=ext4 ip=dhcp nfsroot=192.168.4.9:/mnt/pxe/rootfs,v3 ro rootwait

My NFS server is working, I am able to mount the rootfs from different board (also rockpi4a) in the same network (using command line).

I am really stuck here, could anyone help? Thank you in advance. The serial console log ends with (as a new user, I was not able to post the entire console log):

Starting kernel …

[ 1.899002] bootconsole [uart0] disabled

…nothing happens here - the ‘ss -a|grep nfs’ on the NFS server does not show any new client connections and I haven’t found a way how to find the reason of the malfunction since there are no logs after the kernel disables bootconsole (I’ve googled a lot but without success).

Paste the full log at: https://paste.ubuntu.com/ and send the link here.

Here it is:

full boot log: https://paste.ubuntu.com/p/6Jy67bYgHs/

In the hw_intfc.conf there are all default values, i.e.:


intfc:pwm0=off
intfc:pwm1=off
intfc:uart2=off
intfc:uart4=off
intfc:spi1=on
intfc:spi2=off
intfc:i2c2=off
intfc:i2c6=off
intfc:i2c7=off

intfc:dtoverlay=console-on-ttyS2

#intfc:dtoverlay=console-on-ttyS4

…paste.ubuntu.com needs login, so I’ve put the log to the pastebin: https://pastebin.com/7a48gzyM
thank you for any help - I am stuck on it with rockpi4a unable to boot as diskless device.