[Intel-gfx] REGRESSION in c5552fde102f ("nvme: Enable autonomous power state transitions")

[Ville Syrjälä]

On Wed, Jan 24, 2018 at 01:42:08PM +0200, Jani Nikula wrote:
> 
> Hi Andy, all -
> 
> So this is an odd one.
> 
> I'm getting display FIFO underruns in a very specific setting: Laptop
> display switched off, and an external display connected. Other
> combinations work fine.
> 
> I've bisected this to c5552fde102f ("nvme: Enable autonomous power state
> transitions"), and, being baffled by the result, carefully checked
> this. There are no problems when running c5552fde102f^, with
> nvme_core.default_ps_max_latency_us=0, or after 'echo 0 >
> pm_qos_latency_tolerance_us'. With the last one, restoring the original
> value of 100000 brings the underruns back.
> 
> I have no idea what the root cause mechanism here is, but the bisect is
> correct. Perhaps something to do with timing. I'd be happy to provide
> further details.
> 
> I see that you have quirked one Samsung device. Incidentally, this
> Lenovo Yoga 910 (Kabylake, SunrisePoint LP PCH) also has a Samsung NVMe
> device, just a different one. Details below. I don't know what the
> failure mode in the quirked one is, so I don't know if this could be the
> same issue.

My first gut feeling would be that by allowing the nvme to go to sleep
we're gettting into some deeper power saving state, which then causes
display underruns. How does the package c-state residency look
before/after the commit?

I might be wrong too of course. IIRC there were plenty of display
flicker issues on SKL at least that were magically fixed by unknown
magic in BIOS updates.

> 
> BR,
> Jani.
> 
> 
> $ lspci -vvnn -s 02:00.0
> 02:00.0 Non-Volatile memory controller [0108]: Samsung Electronics Co Ltd Device [144d:a804] (prog-if 02 [NVM Express])
> 	Subsystem: Samsung Electronics Co Ltd Device [144d:a801]
> 	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 16
> 	NUMA node: 0
> 	Region 0: Memory at a1200000 (64-bit, non-prefetchable) [size=16K]
> 	Capabilities: [40] 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: [50] MSI: Enable- Count=1/32 Maskable- 64bit+
> 		Address: 0000000000000000  Data: 0000
> 	Capabilities: [70] Express (v2) Endpoint, MSI 00
> 		DevCap:	MaxPayload 256 bytes, PhantFunc 0, Latency L0s unlimited, L1 unlimited
> 			ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset+ SlotPowerLimit 25.000W
> 		DevCtl:	Report errors: Correctable+ Non-Fatal+ Fatal+ Unsupported+
> 			RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ FLReset-
> 			MaxPayload 256 bytes, MaxReadReq 512 bytes
> 		DevSta:	CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr+ TransPend-
> 		LnkCap:	Port #0, Speed 8GT/s, Width x4, ASPM L1, Exit Latency L0s unlimited, L1 <64us
> 			ClockPM+ Surprise- LLActRep- BwNot- ASPMOptComp+
> 		LnkCtl:	ASPM L1 Enabled; RCB 64 bytes Disabled- CommClk+
> 			ExtSynch- ClockPM+ AutWidDis- BWInt- AutBWInt-
> 		LnkSta:	Speed 8GT/s, Width x4, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
> 		DevCap2: Completion Timeout: Range ABCD, TimeoutDis+, LTR+, OBFF Not Supported
> 		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: -6dB, EqualizationComplete+, EqualizationPhase1+
> 			 EqualizationPhase2+, EqualizationPhase3+, LinkEqualizationRequest-
> 	Capabilities: [b0] MSI-X: Enable+ Count=33 Masked-
> 		Vector table: BAR=0 offset=00003000
> 		PBA: BAR=0 offset=00002000
> 	Capabilities: [100 v2] Advanced Error Reporting
> 		UESta:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
> 		UEMsk:	DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
> 		UESvrt:	DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
> 		CESta:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr-
> 		CEMsk:	RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
> 		AERCap:	First Error Pointer: 00, GenCap+ CGenEn- ChkCap+ ChkEn-
> 	Capabilities: [148 v1] Device Serial Number 00-00-00-00-00-00-00-00
> 	Capabilities: [158 v1] Power Budgeting <?>
> 	Capabilities: [168 v1] #19
> 	Capabilities: [188 v1] Latency Tolerance Reporting
> 		Max snoop latency: 3145728ns
> 		Max no snoop latency: 3145728ns
> 	Capabilities: [190 v1] L1 PM Substates
> 		L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
> 			  PortCommonModeRestoreTime=10us PortTPowerOnTime=10us
> 		L1SubCtl1: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+
> 			   T_CommonMode=0us LTR1.2_Threshold=163840ns
> 		L1SubCtl2: T_PwrOn=44us
> 	Kernel driver in use: nvme
> 	Kernel modules: nvme
> 
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center
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-- 
Ville Syrjälä
Intel OTC