Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Does this indicates that memory space (Mem-) and bus mastering (BusMaster-) are disabled? Does it suggest the device might have entered a low-power state? I see runtime_status as active #cat /sys/bus/pci/devices/0000\:01\:00.0/power/runtime_status active On Fri, Jan 31, 2025 at 3:37 PM Naveen Kumar P <naveenkumar.parna@xxxxxxxxx> wrote: > > Dear Linux Kernel Community, > > I hope this message finds you well. I am reaching out to seek assistance with an issue I am experiencing with a PCIe device on my system. > > System Details: > > PCIe Device: PLDA Device 5555 > Kernel Version: 5.4.0-148-generic > Distribution: Ubuntu 20.04.6 LTS > > After booting the system, I read the Base Address Register (BAR) of the PCIe device using the following command: > > setpci -s 01:00.0 BASE_ADDRESS_0 > > Initially, the BAR value is 0xb0400000. However, after some time, reading from the PCIe device's BAR memory fails and returns 0xffff (PCIe memory-mapped registers read via the readb(), readw(), and readl() kernel mode APIs returned 0xff\0xffff\0xffffffff). Upon rechecking the BAR using the same setpci command, the result is 0x00000000. Additionally, I verified the BAR0 address using the kernel API pci_resource_start(), and it exhibited the same behavior. > > Steps Taken: > > Verified the device status using lspci -vvv -s 01:00.0: > # lspci -vvv -s 01:00.0 > 01:00.0 RAM memory: PLDA Device 5555 > Subsystem: Device 4000:0000 > 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- > Interrupt: pin A routed to IRQ 16 > Region 0: Memory at b0400000 (32-bit, non-prefetchable) [virtual] [size=4M] > 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: [48] MSI: Enable- Count=1/1 Maskable- 64bit- > Address: 00000000 Data: 0000 > Capabilities: [60] Express (v2) Endpoint, MSI 00 > DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s unlimited, L1 unlimited > ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset- SlotPowerLimit 0.000W > DevCtl: CorrErr- NonFatalErr- FatalErr- UnsupReq- > RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ > MaxPayload 128 bytes, MaxReadReq 512 bytes > DevSta: CorrErr+ NonFatalErr- FatalErr- UnsupReq- AuxPwr- TransPend- > LnkCap: Port #0, Speed 2.5GT/s, Width x2, ASPM L0s, Exit Latency L0s unlimited > ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp- > LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk- > ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt- > LnkSta: Speed 2.5GT/s (ok), Width x2 (ok) > TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt- > DevCap2: Completion Timeout: Range B, TimeoutDis-, NROPrPrP-, LTR- > 10BitTagComp-, 10BitTagReq-, OBFF Not Supported, ExtFmt-, EETLPPrefix- > EmergencyPowerReduction Not Supported, EmergencyPowerReductionInit- > FRS-, TPHComp-, ExtTPHComp- > AtomicOpsCap: 32bit- 64bit- 128bitCAS- > DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled > AtomicOpsCtl: ReqEn- > LnkCtl2: Target Link Speed: 2.5GT/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- > Kernel driver in use: M1801 PCI > Kernel modules: m1801_pci > > # lspci -xxx -s 01:00.0 > 01:00.0 RAM memory: PLDA Device 5555 > 00: 56 15 55 55 00 00 10 00 00 00 00 05 00 00 00 00 > 10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 40 00 00 > 30: 00 00 00 00 40 00 00 00 00 00 00 00 ff 01 00 00 > 40: 01 48 03 00 08 00 00 00 05 60 00 00 00 00 00 00 > 50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 60: 10 00 02 00 c2 8f 00 00 10 28 01 00 21 f4 03 00 > 70: 00 00 21 00 00 00 00 00 00 00 00 00 00 00 00 00 > 80: 00 00 00 00 02 00 00 00 00 00 00 00 00 00 00 00 > 90: 20 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 > a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > > Verified power management settings: > > cat /sys/module/pcie_aspm/parameters/policy > Output: [default] performance powersave powersupersave > > > Request for Assistance: I would appreciate any guidance or suggestions on how to further debug this issue. Specifically, I am looking for: > > Potential causes for the BAR being reset to 0x00000000. > Steps to ensure the device is not being reset or put into a low-power state unexpectedly. > Any additional diagnostic steps or tools that could help identify the root cause. > Thank you for your time and assistance. > > > Best regards, > Naveen > > >
