I dont know what can be the cause of this, I just added the i915 parameters to the kernel line and as soon as I login I get a lot of warnings and errors that eventually locks up the laptop (lenovo t420s, intel i5) and I have to power it down.

I pasted the kern.log on a pastebin, here is the link: http://pastebin.com/F6ni2Fha

On that log file some lines appear to be interesting, this lines appear just before the laptop locks up:

Code:
Apr  3 18:12:06 bt kernel: [   71.174171] Call Trace:
Apr  3 18:12:06 bt kernel: [   71.174172]  [<ffffffff81065bef>] warn_slowpath_common+0x7f/0xc0
Apr  3 18:12:06 bt kernel: [   71.174174]  [<ffffffff81065c4a>] warn_slowpath_null+0x1a/0x20
Apr  3 18:12:06 bt kernel: [   71.174176]  [<ffffffff8151a584>] __domain_mapping+0x334/0x370
Apr  3 18:12:06 bt kernel: [   71.174178]  [<ffffffff8151c3c3>] __intel_map_single+0x113/0x240
Apr  3 18:12:06 bt kernel: [   71.174180]  [<ffffffff8151c523>] intel_map_page+0x33/0x40
Apr  3 18:12:06 bt kernel: [   71.174184]  [<ffffffffa01ba735>] iwlagn_rx_allocate+0x65/0x280 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174188]  [<ffffffffa01bc313>] iwlagn_rx_replenish+0x23/0x60 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174192]  [<ffffffffa01b8faf>] iwl_trans_pcie_start_device+0x22f/0x1150 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174196]  [<ffffffffa01a2b11>] iwlagn_load_ucode_wait_alive+0x31/0x3e0 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174198]  [<ffffffff8103bf89>] ? default_spin_lock_flags+0x9/0x10
Apr  3 18:12:06 bt kernel: [   71.174202]  [<ffffffffa01aad87>] ? iwlagn_alloc_bcast_station+0xc7/0x140 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174206]  [<ffffffffa019c0cc>] iwlagn_mac_start+0x11c/0x220 [iwlwifi]
Apr  3 18:12:06 bt kernel: [   71.174212]  [<ffffffffa00ef6e3>] ieee80211_do_open+0x283/0x740 [mac80211]
Apr  3 18:12:06 bt kernel: [   71.174213]  [<ffffffff81640d86>] ? notifier_call_chain+0x56/0x80
Apr  3 18:12:06 bt kernel: [   71.174219]  [<ffffffffa00efbe9>] ieee80211_open+0x49/0x90 [mac80211]
Apr  3 18:12:06 bt kernel: [   71.174222]  [<ffffffff815371d7>] __dev_open+0xa7/0xf0
Apr  3 18:12:06 bt kernel: [   71.174224]  [<ffffffff81535eb1>] __dev_change_flags+0xa1/0x180
Apr  3 18:12:06 bt kernel: [   71.174226]  [<ffffffff815370e8>] dev_change_flags+0x28/0x70
Apr  3 18:12:06 bt kernel: [   71.174227]  [<ffffffff8159fe74>] devinet_ioctl+0x624/0x6e0
Apr  3 18:12:06 bt kernel: [   71.174229]  [<ffffffff815a12b0>] inet_ioctl+0x90/0xb0
Apr  3 18:12:06 bt kernel: [   71.174231]  [<ffffffff81521ac0>] sock_do_ioctl+0x30/0x60
Apr  3 18:12:06 bt kernel: [   71.174233]  [<ffffffff81521b69>] sock_ioctl+0x79/0x2b0
Apr  3 18:12:06 bt kernel: [   71.174234]  [<ffffffff81188da4>] do_vfs_ioctl+0xa4/0x580
Apr  3 18:12:06 bt kernel: [   71.174236]  [<ffffffff810dee15>] ? call_rcu_sched+0x15/0x20
Apr  3 18:12:06 bt kernel: [   71.174238]  [<ffffffff81189321>] sys_ioctl+0xa1/0xb0
Apr  3 18:12:06 bt kernel: [   71.174240]  [<ffffffff816450c2>] system_call_fastpath+0x16/0x1b
Apr  3 18:12:06 bt kernel: [   71.174241] ---[ end trace e81bb2f6035df524 ]---
This doesnt happen on the "recovery" Kernel.

Any help would be greatly appreaciated.