Ubuntu – Failed to suspend due to nouveau failure

There are many questions about failed suspension on ubuntu ([1][2]), but each
of them seem so specific that I'm posting mine.
In my case, sometimes (very randomly) my XP15 does not suspend.
I'm running Ubuntu 14.04 updated to current date.
My syslog states:

Aug 12 23:20:24 ged kernel: [32564.982253] Suspending console(s) (use no_console_suspend to debug)
Aug 12 23:20:24 ged kernel: [32564.982580] sd 1:0:0:0: [sdb] Synchronizing SCSI cache
Aug 12 23:20:24 ged kernel: [32564.982615] sd 0:0:0:0: [sda] Synchronizing SCSI cache
Aug 12 23:20:24 ged kernel: [32564.984880] sd 0:0:0:0: [sda] Stopping disk
Aug 12 23:20:24 ged kernel: [32564.985451] sd 1:0:0:0: [sdb] Stopping disk
Aug 12 23:20:24 ged kernel: [32565.032197] nouveau  [     DRM] suspending display...
Aug 12 23:20:24 ged kernel: [32565.032205] nouveau  [     DRM] unpinning framebuffer(s)...
Aug 12 23:20:24 ged kernel: [32565.032208] nouveau  [     DRM] evicting buffers...
Aug 12 23:20:24 ged kernel: [32565.032210] nouveau  [     DRM] waiting for kernel channels to go idle...
Aug 12 23:20:24 ged kernel: [32565.032250] nouveau  [     DRM] suspending client object trees...
Aug 12 23:20:24 ged kernel: [32565.033027] nouveau  [     DRM] suspending kernel object tree...
Aug 12 23:20:24 ged kernel: [32567.035761] nouveau E[   PDISP][0000:01:00.0][0xc000857c][ffff88042386bb80] fini timeout, 0xc2061008
Aug 12 23:20:24 ged kernel: [32567.035764] nouveau E[   PDISP][0000:01:00.0][0xc000857c][ffff88042386bb80] failed suspend, -16
Aug 12 23:20:24 ged kernel: [32567.035766] nouveau E[     DRM] 0xd1500000:0xd15c7c00 suspend failed with -16
Aug 12 23:20:24 ged kernel: [32567.035804] nouveau E[     DRM] 0xdddddddd:0xd1500000 suspend failed with -16
Aug 12 23:20:24 ged kernel: [32567.035922] nouveau E[     DRM] 0xffffffff:0xdddddddd suspend failed with -16
Aug 12 23:20:24 ged kernel: [32567.036633] nouveau E[     DRM] 0xffffffff:0xffffffff suspend failed with -16
Aug 12 23:20:24 ged kernel: [32567.036757] nouveau  [     DRM] resuming display...
Aug 12 23:20:24 ged kernel: [32567.036785] nouveau E[     DRM] bo ffff880036980000 pinned elsewhere: 0x00000002 vs 0x00000004
Aug 12 23:20:24 ged kernel: [32567.036788] [drm:drm_helper_resume_force_mode] *ERROR* failed to set mode on crtc ffff88041f020000
Aug 12 23:20:24 ged kernel: [32567.044935] pci_pm_suspend(): nouveau_pmops_suspend+0x0/0xb0 [nouveau] returns -16
Aug 12 23:20:24 ged kernel: [32567.044939] dpm_run_callback(): pci_pm_suspend+0x0/0x150 returns -16
Aug 12 23:20:24 ged kernel: [32567.044945] PM: Device 0000:01:00.0 failed to suspend async: error -16
Aug 12 23:20:24 ged kernel: [32567.045007] PM: Some devices failed to suspend, or early wake event detected

As it seems the problem is on the video card.
The result from lspci | grep VGA returns.

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 GF108M [GeForce GT 540M] (rev a1)

Which is strange, is that I'm not using the NVIDIA card (since both nouveau and official drivers are not stable in my machine).

Any hints for a next step?