[U-Boot] Riscv: CONFIG_DEFAULT_DEVICE_TREE failures

[Troy Benjegerdes]

I attempted to merge in the latest master branch into
https://github.com/sifive/u-boot/tree/sandbox and I got
the following error, which seems somewhat broken..


Device Tree Source is not correctly specified.
Please define 'CONFIG_DEFAULT_DEVICE_TREE'
or build with 'DEVICE_TREE=<device_tree>' argument

dts/Makefile:28: recipe for target 'arch/riscv/dts/fu540.dtb' failed


Does anyone have any idea what would have caused that?

Also any feedback or pointers on why the serial_sifive.c 
driver with CONFIG_DM_SERIAL would not work, but serial_hifive.c
without CONFIG_DM_SERIAL does seem to work might be appreciated.