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.
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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