CEC not working at boot on Panasonic Viera

[Fabio72]

Software
XBian version: XBian 1.0 (knockout)
XBMC/Kodi version: 14.2-BETA2 Git:Unknown
Overclock settings: Medium

Hardware
Device type and model: Raspberry Pi Model B+
Power supply rating: 2A (white raspberry)
SD card size and make/type: 8Gb samsung evo + nfs root
Network (Ethernet or wireless): wired
Connected devices (TV, USB, network storage, ...): Panasonic Viera TX-P42X60

Log files
Link to logfile(s):
no errors logged

Problem description:
When Xbian starts, most of times CEC doesn't work.
I have to do the following actions on TV: Set link(*) to off, exit tv menu, set link to on again. Then CEC start working without any problem.
If I reboot Xbian, with TV on, sometimes CEC works immediately, but more often I must do the menu trick again.

Then I can switch off and on TV and, as long Xbian is running, CEC works everytime.

But sometimes even doing the link off/on procedure, CEC doesn't start working, unless I reboot Xbian with tv on.

When kodi starts I can always see the message of CEC peripheral connected.

(*) I don't use the so called "Viera link" because is not working (I think is searching only other Panasonic stuff). There's another link item in TV menus.

How to reproduce:
Switch TV off
reboot Xbian and let kodi start
Switch TV on

I have this problem since I left beta 2