Created attachment 114723 [details]
dmesg with drm.debug info

System Environment:       
-----------------------------------------------------
Regression: Yes, 
Non-working platforms: PNV SNB IVB BYT 

==Kernel==
--------------------------------------------------
commit 07e5c9b5061ad65c85285c0bb9ecd5626ed301d0
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Mar 27 15:29:51 2015 +0100

drm-intel-nightly: 2015y-03m-27d-14h-29m-07s UTC integration manifest

==Bug detailed description==
Igt/kms_setmode subcases clone-exclusive-crtc and clone-single-crtc causes time out and call trace on SNB mobile, it does not exists on SNB desktop,

By bisected, shows the first bad commit is 0b9018.
commit 0b9018793939970aad49e4e0ed21f0fd0db74e4a
Author:     Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
AuthorDate: Fri Mar 20 16:18:08 2015 +0200
Commit:     Daniel Vetter <daniel.vetter@ffwll.ch>
CommitDate: Thu Mar 26 17:49:52 2015 +0100

    drm/i915: Don't use encoder->new_crtc in intel_modeset_pipe_config()
    
    Move towards atomic by using the legacy modeset's drm_atomic_state
    instead.
    
    v2: Move call to drm_atomic_add_affected_connectors() to
        intel_modeset_compute_config(). (Daniel)

Output:
[  127.901701] Call Trace:
[  127.901722]  [<ffffffffa00d26e8>] ? intel_modeset_compute_config+0x5b8/0xd51 [                                                                                       i915]
[  127.901760]  [<ffffffffa00d4cb9>] ? intel_set_mode+0x39/0x91 [i915]
[  127.901792]  [<ffffffffa00d5df8>] ? intel_crtc_set_config+0xb8a/0xc55 [i915]
[  127.901821]  [<ffffffff81791d97>] ? printk+0x48/0x4d
[  127.901848]  [<ffffffffa000c1e7>] ? drm_mode_set_config_internal+0x4e/0xd2 [dr                                                                                       m]
[  127.901882]  [<ffffffffa000febf>] ? drm_mode_setcrtc+0x3fe/0x4f4 [drm]
[  127.901913]  [<ffffffffa00047d4>] ? drm_ioctl+0x344/0x3b3 [drm]
[  127.901941]  [<ffffffffa000fac1>] ? drm_mode_setplane+0x1dc/0x1dc [drm]
[  127.901969]  [<ffffffff8111da12>] ? do_vfs_ioctl+0x360/0x424
[  127.901992]  [<ffffffff810a2634>] ? __audit_syscall_entry+0xb3/0xd3
[  127.902018]  [<ffffffff8100d41f>] ? syscall_trace_enter_phase1+0x11a/0x123
[  127.902045]  [<ffffffff8111db1f>] ? SyS_ioctl+0x49/0x7a
[  127.902066]  [<ffffffff8179ae0e>] ? int_check_syscall_exit_work+0x34/0x3d
[  127.902092]  [<ffffffff8179abf2>] ? system_call_fastpath+0x12/0x17
[  127.902116] Code: c7 44 24 08 18 00 00 00 e9 68 fc ff ff 48 63 44 24 20 49 8b                                                                                        56 38 4c 8b 2c c2 4d 85 ed 0f 84 c6 00 00 00 49 8b 56 40 48 8b 04 c2 <48> 39 58 0                                                                                       8 0f 85 b4 00 00 00 f6 05 58 de f5 ff 04 41 8b 87 34
[  127.902280] RIP  [<ffffffffa00d28b3>] intel_modeset_compute_config+0x783/0xd51                                                                                        [i915]
[  127.902320]  RSP <ffff8800b095fb78>
[  127.902334] CR2: 0000000000000008
[  127.908820] ---[ end trace 77b9184de44fe47f ]---
Reproduce steps:
----------------------------
1, ./kms_setmode --run-subtest invalid-clone-single-crtc