[U-Boot] SPL and DM on ZYNQ

[Hannes Schmelzer <hannes@schmelzer.or.at>]

hi folks,

i am not very familar with driver model until now and so i've a question.

I'm trying to bring up my Zynq ZC702 evalboard using driver-model during 
SPL stage (because QSPI needs this).
I simply switched on "Driver Model for SPL" within Kconfig and compiled.

This ends up in:

U-Boot SPL 2015.10-rc4-00050-g996ec1d-dirty (Oct 07 2015 - 13:57:32)
 >>spl:board_init_r()
using memory 0xffff10c0-0xffff20c0 for malloc()
spl_init()
dm_init() failed: -2
dm_init_and_scan() returned error -2
### ERROR ### Please RESET the board ###


i had a look into drivers/core/root.c and saw that

device_bind_by_name(NULL, false, &root_info, &DM_ROOT_NON_CONST);

fails.

Any idea why the root-driver cannot be found ?
Maybe there are some switched need to be switched on too.

thanks,
Hannes