NVIDIA vgaswitcheroo doesn't work

[carachi diego]

Hello,
I installed yesterday on my laptop the last version of Fedora with 3.12.8
kernel.
However I discover that the discrete GPU (NVIDIA GT520M) remain always on,
reducing battery performance.
I tried to switch it off but seem that vgaswitcheroo doesn't work on it.
How can I solve this problem?
here some commands:

[root@Fedora20 ~]# lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core
Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GF119M [GeForce GT
520M] (rev a1)
[root@Fedora20 ~]# cat /sys/kernel/debug/vgaswitcheroo/switch
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynPwr:0000:01:00.0
[root@Fedora20 ~]# echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
[root@Fedora20 ~]# cat /sys/kernel/debug/vgaswitcheroo/switch
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynPwr:0000:01:00.0
[root@Fedora20 ~]# uname -a
Linux Fedora20 3.12.8-300.fc20.x86_64 #1 SMP Thu Jan 16 01:07:50 UTC 2014
x86_64 x86_64 x86_64 GNU/Linux


Thank you very much
C.

-- 
http://www.2dd.it