Hi,

while upgrading to a recent version of barebox, I've encountered the
problem that booting an AM335x board via network does no longer work.
The MLO fails to chain-load barebox.bin, it doesn't even send a request
to the TFTP-Server to retrieve the main bootloader file.

Working through the Git history, I've been able to pinpoint the problem
as follows (using output from "git describe"):

- On the topic branch which introduced the bug, v2017.11.0-11-g946bc95a4
was the last working version.

- From v2017.11.0-12-gab84733e5 up to v2017.11.0-14-g6b4a38d00, the MLO
neither produces any outputs on the UART0 nor chain-loads barebox.bin.

- Since version v2017.11.0-15-g528298b70, the MLO produces the following
output:

> barebox 2017.11.0 #1 Wed Sep 12 07:23:48 UTC 2018
>
>
> Board: Phytec phyCORE AM335x
> cpsw 4a100000.ethernet: detected phy mask 0x1
> mdio_bus: miibus0: probed
> eth0: got preset MAC address: c4:f3:12:e7:cb:9c
> booting from NET
> eth0: got preset MAC address: c4:f3:12:e7:cb:9c
> eth0: 100Mbps full duplex link detected
> eth0: DHCP client bound to address 192.168.4.52
> bootfile not found.
> booting failed

The master branch includes the problem as of v2017.12.0-90-g3dbe78ab5,
so that the first official release with this behavior has been v2018.01.0.

The bug still persists in v2018.09.0.

The board-specific MLO I've been using is this:
barebox-am33xx-phytec-phycore-r2-mlo-512mb.img

Let me know if you need further information in order to reproduce and/or
fix the problem.

Thanks in advance, and best regards,
Dennis Menschel