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Message-ID: <CAMciSVUzFL+myQTTRD-OZRf+o9UUPDE87SzUxQ2cYdjrfd7iHQ@mail.gmail.com>
Date: Fri, 31 Jan 2025 15:37:26 +0530
From: Naveen Kumar P <naveenkumar.parna@...il.com>
To: linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>
Subject: Assistance Needed: PCIe Device BAR Reset Issue
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
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