[Nouveau] PROBLEM: new kernel 3.15.0-rc8 hangs completely with CONFIG_DRM_NOUVEAU enabled

[Christian Wehrmeyer]

Hello, guys.
First apologize my flaws, I am not a native English speaker and thus am
prone to stupid errors.

My box is an ASUSTek Notebook with Optimus capability (no, this is NOT
about Optimus, I don't try to use Optimus yet, so please don't switch
off here) with a running Gentoo. The first GPU is an Haswell-based Intel
chip, the second one is a nVidia GeForce GTX 850M, the chip is a GM107M,
which I understand to be a NV110.
So far I have been using the 3.14.8 kernel without CONFIG_DRM_NOUVEAU
enabled, as it was lacking of the maxwell support you guys added in May
2014. Today I wanted to try if I could use my card with the nouveau
driver (no particular purpose in general, I just thought I could somehow
support you guys. Xorg is told NOT to use any GPU except for the Intel one).

Yet, the 3.15.0-rc8 which I downloaded this evening crashes on me when
compiled with the CONFIG_DRM_NOUVEAU flag enabled during compilation.
Crashes means: xdm starts, slim starts, I login to my Gentoo box, open a
terminal emulator instance (exo-open --launch TerminalEmulator), and try
to open /var/log/kern.log for any error messages - and if I got halfway
through tipping that command, I'll be a lucky man. The notebook suddenly
and unexpectedly hangs during these actions, the mouse does not
response, the keyboard does not response, the display manager freezes
completely (I can say that by a CPU usage tool that runs in my Xfce, and
it freezes as well, so it's not just the input devices getting
disconnected). ALT+SysReq+s/b does not work, syncing/rebooting fails, it
does absolutely nothing. Disabling the CONFIG_DRM_NOUVEAU flag and
recompiling removes the hang completely. I can reproduce the problem by
just rebooting and logging in as descriped above.

Files within the attached tar.gz:
config-3.15.0-rc8-valhalla.old [non-working configuration]
config-3.15.0-rc8-valhalla [working configuration]
kern.log.old: Shows the boot process with the non-working configuration
kern.log: Shows the boot process with the working configuration

The output of lshw:

description: Notebook
product: N550JK (ASUS-NotebookSKU)
vendor: ASUSTeK COMPUTER INC.
version: 1.0
serial: <scrubed>
width: 64 bits
capabilities: smbios-2.7 dmi-2.7 ldt16 vsyscall32
configuration: boot=normal chassis=notebook family=N
sku=ASUS-NotebookSKU uuid=<scrubed>

Output of lspci -vvvvvk, everything not-VGA-like scrubed off:

00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core
Processor Integrated Graphics Controller (rev 06) (prog-if 00 [VGA
controller])
	Subsystem: ASUSTeK Computer Inc. Device 11cd
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 40
	Region 0: Memory at f7400000 (64-bit, non-prefetchable) [size=4M]
	Region 2: Memory at d0000000 (64-bit, prefetchable) [size=256M]
	Region 4: I/O ports at f000 [size=64]
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
		Address: feeff00c  Data: 4181
	Capabilities: [d0] Power Management version 2
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [a4] PCI Advanced Features
		AFCap: TP+ FLR+
		AFCtrl: FLR-
		AFStatus: TP-
	Kernel driver in use: i915

01:00.0 3D controller: NVIDIA Corporation GM107M [GeForce GTX 850M] (rev a2)
	Subsystem: ASUSTeK Computer Inc. Device 11cd
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 11
	Region 0: Memory at f6000000 (32-bit, non-prefetchable) [size=16M]
	Region 1: Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Region 3: Memory at f0000000 (64-bit, prefetchable) [size=32M]
	Region 5: I/O ports at e000 [size=128]
	Expansion ROM at f7000000 [disabled] [size=512K]
	Capabilities: [60] Power Management version 3
		Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
		Address: 0000000000000000  Data: 0000
	Capabilities: [78] Express (v2) Endpoint, MSI 00
		DevCap:	MaxPayload 256 bytes, PhantFunc 0, Latency L0s unlimited, L1 <64us
			ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
		DevCtl:	Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
			RlxdOrd- ExtTag+ PhantFunc- AuxPwr- NoSnoop+
			MaxPayload 256 bytes, MaxReadReq 512 bytes
		DevSta:	CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
		LnkCap:	Port #0, Speed 8GT/s, Width x16, ASPM L0s L1, Latency L0 <1us,
L1 <4us
			ClockPM+ Surprise- LLActRep- BwNot-
		LnkCtl:	ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk+
			ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
		LnkSta:	Speed 8GT/s, Width x16, TrErr- Train- SlotClk+ DLActive-
BWMgmt- ABWMgmt-
		DevCap2: Completion Timeout: Range AB, TimeoutDis+, LTR+, OBFF Via message
		DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR+, OBFF
Disabled
		LnkCtl2: Target Link Speed: 8GT/s, EnterCompliance- SpeedDis-
			 Transmit Margin: Normal Operating Range, EnterModifiedCompliance-
ComplianceSOS-
			 Compliance De-emphasis: -6dB
		LnkSta2: Current De-emphasis Level: -3.5dB, EqualizationComplete+,
EqualizationPhase1+
			 EqualizationPhase2-, EqualizationPhase3-, LinkEqualizationRequest-

I will provide you with additional informations if you need them, just
let me know.

With best regards,
Christian Wehrmeyer from Germany
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