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SubjectRe: [PATCH V6 02/15] PCI/PME: Export pcie_pme_disable_msi() & pcie_pme_no_msi() APIs
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On 5/17/2019 6:54 PM, Bjorn Helgaas wrote:
> On Fri, May 17, 2019 at 01:49:49PM +0530, Vidya Sagar wrote:
>> On 5/16/2019 7:04 PM, Bjorn Helgaas wrote:
>>> On Tue, May 14, 2019 at 09:00:19AM +0530, Vidya Sagar wrote:
>>>> On 5/13/2019 12:55 PM, Christoph Hellwig wrote:
>>>>> On Mon, May 13, 2019 at 10:36:13AM +0530, Vidya Sagar wrote:
>>>>>> Export pcie_pme_disable_msi() & pcie_pme_no_msi() APIs to enable drivers
>>>>>> using these APIs be able to build as loadable modules.
>>>>>
>>>>> But this is a global setting. If you root port is broken you need
>>>>> a per-rootport quirk instead.
>>>>>
>>>> There is nothing broken in Tegra194 root port as such, rather, this
>>>> is more of software configuration choice and we are going with
>>>> legacy interrupts than MSI interrupts (as Tegra194 doesn't support
>>>> raising PME interrupts through MSI and please note that this doesn't
>>>> mean root port is broken).
>>>
>>> I think the port *is* broken. PCIe r4.0, sec 6.1.6, says
>>>
>>> If the Root Port is enabled for edge-triggered interrupt signaling
>>> using MSI or MSI-X, an interrupt message must be sent every time the
>>> logical AND of the following conditions transitions from FALSE to
>>> TRUE:
>>>
>>> * The associated vector is unmasked (not applicable if MSI does
>>> not support PVM).
>>>
>>> * The PME Interrupt Enable bit in the Root Control register is set
>>> to 1b.
>>>
>>> * The PME Status bit in the Root Status register is set.
>>>
>>> The Tegra194 root port advertises MSI support, so the above should
>>> apply.
>> I had a discussion with our hardware engineers and we are of the
>> opinion that the root port is not really broken w.r.t MSI as spec
>> doesn't clearly say that if root port advertises MSI support, it
>> must generate MSI interrupts for PME. All that it says is, if MSI is
>> enabled, then MSI should be raised for PME events. Here, by
>> 'enable', we understand that as enabling at hardware level to
>> generate MSI interrupt which is not the case with Tegra194. In
>> Tegra194, root port is enabled to generate MSI only for hot-plug
>> events and legacy interrupts are used for PME, AER.
>
> Do you have "lspci -vvxxx" output for the root ports handy?
>
> If there's some clue in the standard config space that would tell us
> that MSI works for some events but not others, we could make the PCI
> core pay attention it. That would be the best solution because it
> wouldn't require Tegra-specific code.

Here is the output of 'lspci vvxxx' for one of Tegra194's root ports.

0005:00:00.0 PCI bridge: NVIDIA Corporation Device 1ad0 (rev a1) (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
Interrupt: pin A routed to IRQ 50
Bus: primary=00, secondary=01, subordinate=ff, sec-latency=0
I/O behind bridge: None
Memory behind bridge: 40000000-400fffff [size=1M]
Prefetchable memory behind bridge: None
Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- <SERR- <PERR-
BridgeCtl: Parity- SERR+ NoISA- VGA- VGA16- MAbort- >Reset- FastB2B-
PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
Capabilities: [40] Power Management version 3
Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
Address: 0000000000000000 Data: 0000
Masking: 00000000 Pending: 00000000
Capabilities: [70] Express (v2) Root Port (Slot-), MSI 00
DevCap: MaxPayload 256 bytes, PhantFunc 0
ExtTag- RBE+
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 16GT/s, Width x8, ASPM L0s L1, Exit Latency L0s <1us, L1 <64us
ClockPM- Surprise+ LLActRep+ BwNot+ ASPMOptComp+
LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt+ AutBWInt-
LnkSta: Speed 5GT/s (downgraded), Width x1 (downgraded)
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-
AtomicOpsCap: Routing- 32bit- 64bit- 128bitCAS-
DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR+, OBFF Disabled ARIFwd-
AtomicOpsCtl: ReqEn- EgressBlck-
LnkCtl2: Target Link Speed: 16GT/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=8 Masked-
Vector table: BAR=2 offset=00000000
PBA: BAR=2 offset=00010000
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- AdvNonFatalErr-
CEMsk: RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr+
AERCap: First Error Pointer: 00, ECRCGenCap+ ECRCGenEn- ECRCChkCap+ ECRCChkEn-
MultHdrRecCap+ MultHdrRecEn- TLPPfxPres- HdrLogCap-
HeaderLog: 00000000 00000000 00000000 00000000
RootCmd: CERptEn+ NFERptEn+ FERptEn+
RootSta: CERcvd- MultCERcvd- UERcvd- MultUERcvd-
FirstFatal- NonFatalMsg- FatalMsg- IntMsg 0
ErrorSrc: ERR_COR: 0000 ERR_FATAL/NONFATAL: 0000
Capabilities: [148 v1] Secondary PCI Express <?>
Capabilities: [168 v1] Physical Layer 16.0 GT/s <?>
Capabilities: [190 v1] Lane Margining at the Receiver <?>
Capabilities: [1c0 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
PortCommonModeRestoreTime=60us PortTPowerOnTime=40us
L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2- ASPM_L1.1-
T_CommonMode=10us LTR1.2_Threshold=0ns
L1SubCtl2: T_PwrOn=10us
Capabilities: [1d0 v1] Vendor Specific Information: ID=0002 Rev=4 Len=100 <?>
Capabilities: [2d0 v1] Vendor Specific Information: ID=0001 Rev=1 Len=038 <?>
Capabilities: [308 v1] Data Link Feature <?>
Capabilities: [314 v1] Precision Time Measurement
PTMCap: Requester:+ Responder:+ Root:+
PTMClockGranularity: 16ns
PTMControl: Enabled:- RootSelected:-
PTMEffectiveGranularity: Unknown
Capabilities: [320 v1] Vendor Specific Information: ID=0004 Rev=1 Len=054 <?>
Kernel driver in use: pcieport
00: de 10 d0 1a 07 01 10 00 a1 00 04 06 00 00 01 00
10: 00 00 00 00 00 00 00 00 00 01 ff 00 f0 00 00 00
20: 00 40 00 40 f1 ff 01 00 00 00 00 00 00 00 00 00
30: 00 00 00 00 40 00 00 00 00 00 00 00 32 01 02 00
40: 01 50 c3 c9 08 00 00 00 00 00 00 00 00 00 00 00
50: 05 70 80 01 00 00 00 00 00 00 00 00 00 00 00 00
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
70: 10 b0 42 00 01 80 00 00 1f 28 10 00 84 4c 7b 00
80: 40 04 12 f0 00 00 00 00 c0 03 40 00 18 00 01 00
90: 00 00 00 00 1f 0c 01 00 00 04 00 00 1e 00 80 01
a0: 04 00 00 02 00 00 00 00 00 00 00 00 00 00 00 00
b0: 11 00 07 00 02 00 00 00 02 00 01 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

>
> If this situation requires Tegra-specific code, that becomes an issue
> if you ever want to use the part in an ACPI system because the ACPI
> host bridge driver is generic and there isn't a place to put
> device-specific code.
Thanks for bringing it up. I'll make a note of this and discuss about it internally.

>
> Bjorn
>

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