[patchV2 2/2] pci/shpchp: no claim on pcie port device
Pingfan Liu
kernelfans at gmail.com
Mon Jun 25 12:59:31 AEST 2018
On Wed, Jun 13, 2018 at 9:13 PM Bjorn Helgaas <helgaas at kernel.org> wrote:
>
> On Wed, Jun 13, 2018 at 02:29:57PM +0800, Pingfan Liu wrote:
> > The Linux Device Driver Model allows a physical device to be handled
> > by only a single driver. But at present, both shpchp and portdrv_pci
> > claim PCI_CLASS_BRIDGE_PCI, and touch devices_kset when the drivers are
> > loaded. This causes a few problems, one is the wrong shutdown seq of
> > devices, owing to the broken devices_kset. This patch keeps shpchp away
> > from pcie port device, using the extra matching method.
>
> As Christoph pointed out, something seems wrong if we add to
> devices_kset even when the probe fails. We will call shpc_probe() for
> the device below, but there's no SHPC capability, so the probe should
> fail when shpc_init() fails.
>
> I do think the current structure where portdrv and shpchp are both
> "drivers" that claim bridges is broken. This has caused problems
> before, e.g., some PCIe switches have performance counters, and a
> driver for those switches ought to be able to claim the device and use
> the counters, but portdrv is in the way.
>
> I think it would be better if portdrv (and maybe shpchp; not sure
> about that) were integrated into the PCIe core and did not register as
> a driver. But this is a big project, far beyond the scope of this
> current issue.
>
Yes, I agree. But just leaving this for later fix, and try to bring
out a fix in drivers/core firstly.
Regards,
Pingfan
> > Note:
> > I hit this bug on a Power9 machine, when "kexec -e", and see a ata-disk
> > behind a bridge can not write back buffer in flight due to the former
> > shutdown of the bridge which clears the BusMaster bit.
> >
> > the device involved:
> > 0004:00:00.0 PCI bridge: IBM Device 04c1 (prog-if 00 [Normal decode])
> > 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
> > NUMA node: 0
> > Bus: primary=00, secondary=01, subordinate=12, sec-latency=0
> > I/O behind bridge: 00000000-00000fff
> > Memory behind bridge: 80000000-ffefffff
> > Prefetchable memory behind bridge: 0006024000000000-0006027f7fffffff
> > Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- <SERR- <PERR-
> > BridgeCtl: Parity- SERR+ NoISA- VGA- MAbort- >Reset- FastB2B-
> > PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
> > 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] Express (v2) Root Port (Slot-), MSI 00
> > DevCap: MaxPayload 512 bytes, PhantFunc 0
> > ExtTag- RBE+
> > DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
> > RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
> > MaxPayload 256 bytes, MaxReadReq 128 bytes
> > DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
> > LnkCap: Port #0, Speed 8GT/s, Width x8, ASPM not supported, Exit Latency L0s <64ns, L1 <1us
> > ClockPM- Surprise- LLActRep+ BwNot+ ASPMOptComp-
> > LnkCtl: ASPM Disabled; RCB 128 bytes Disabled- CommClk-
> > ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
> > LnkSta: Speed 8GT/s, Width x4, TrErr- Train- SlotClk- DLActive+ BWMgmt- ABWMgmt+
> > RootCtl: ErrCorrectable- ErrNon-Fatal- ErrFatal- PMEIntEna- CRSVisible-
> > RootCap: CRSVisible-
> > RootSta: PME ReqID 0000, PMEStatus- PMEPending-
> > DevCap2: Completion Timeout: Range ABCD, TimeoutDis+, LTR-, OBFF Not Supported ARIFwd+
> > DevCtl2: Completion Timeout: 16ms to 55ms, TimeoutDis+, LTR-, OBFF Disabled ARIFwd+
> > 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-
> > Capabilities: [100 v1] 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] #19
> >
> > Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
> > ---
> > drivers/pci/hotplug/shpchp_core.c | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c
> > index 1f0f969..85b4665 100644
> > --- a/drivers/pci/hotplug/shpchp_core.c
> > +++ b/drivers/pci/hotplug/shpchp_core.c
> > @@ -336,6 +336,18 @@ static void shpc_remove(struct pci_dev *dev)
> > kfree(ctrl);
> > }
> >
> > +static int shpc_extra_match(struct pci_dev *pdev)
> > +{
> > + /* do not claim pcie port device */
> > + if (pci_is_pcie(pdev) &&
> > + (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
> > + pci_pcie_type(pdev) == PCI_EXP_TYPE_UPSTREAM ||
> > + pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM))
> > + return -ENODEV;
> > +
> > + return 0;
> > +}
> > +
> > static const struct pci_device_id shpcd_pci_tbl[] = {
> > {PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0)},
> > { /* end: all zeroes */ }
> > @@ -345,6 +357,7 @@ MODULE_DEVICE_TABLE(pci, shpcd_pci_tbl);
> > static struct pci_driver shpc_driver = {
> > .name = SHPC_MODULE_NAME,
> > .id_table = shpcd_pci_tbl,
> > + .extra_match = shpc_extra_match,
> > .probe = shpc_probe,
> > .remove = shpc_remove,
> > };
> > --
> > 2.7.4
> >
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