Re: [RFC PATCH] PCI/portdrv: Support for subtractive decode bridge

From: Honghui Zhang
Date: Mon Feb 11 2019 - 21:57:44 EST

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On Thu, 2019-02-07 at 09:18 -0600, Bjorn Helgaas wrote:
> Hi Honghui,
>
> On Fri, Dec 14, 2018 at 11:40:29AM +0800, honghui.zhang@xxxxxxxxxxxx wrote:
> > From: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>
> >
> > The Class Code for subtractive decode PCI-to-PCI bridge is 060401h,
> > change the class_mask values to make portdrv support this type bridge.
>
> I assume you have a Root Port or Switch Port that supports subtractive
> decode? I'm trying to understand how such a device would work.
>
Hi, Bjorn,

Yes, most of Mediatek's RC device have set the class type as 060401h as
HW default values, include mt2712 and mt7622.

Those RC device work fine with all I have tried EP device except that
the portdrv was not attached to those device. But no scenario need those
service as far as I know.

> Out of curiosity, can you show the "lspci -vv" output for the device
> and the downstream devices of interest?
>
lspci only read the class type 0604h, it does not care about the
subordinate values of the class type. I will put the "lspci -vv" output
at bottom of this mail.

> Do you happen to know whether this functionality is configurable,
> e.g., is there some way software can enable or disable subtractive
> decode? I assume this would be some device-specific thing, because I
> can't find anything in the Bridge Control register or similar. The
> PCIe spec doesn't even contain the word "subtractive".
>

Those class type values for Mediatek's RC has a register which could be
used to change its values. We never touch this backdoor register since
without the portdrv attached is fine, nobody ask for the port service
yet.

I did some homework for the subtractive decode PCI-to-PCI bridge, and
did not found much more information about that. I guess those port
service should also support subtractive bridge since spec does not
forbidden that.

> The "PCI Express to PCI/PCI-X Bridge Specification", r1.0, says a PCI
> Express bridge (which would include Root Ports and Switch Ports) has a
> Class Code of 0x060400 (Non-Subtractive PCI-PCI Bridge) (sec 1.1).
>
> Sec 1.3.4 says subtractive decode on the primary interface is "not
> applicable or outside the scope of this spec".
>
> Bjorn
>

# lspci -vvv
00:01.0 Class 0604: Device 14c3:5396
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 264
Region 0: Memory at <unassigned> (64-bit, prefetchable)
Bus: primary=00, secondary=01, subordinate=01, sec-latency=64
I/O behind bridge: 00000000-00000fff
Memory behind bridge: 20000000-206fffff
Prefetchable memory behind bridge: 00000000-000fffff
Secondary status: 66MHz+ FastB2B- ParErr- DEVSEL=slow >TAbort-
<TAbort- <MAbort+ <SERR- <PERR-
BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
Address: 000000000807a0c0 Data: 0000
Capabilities: [78] 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: [80] Express (v2) Root Port (Slot+), MSI 01
DevCap: MaxPayload 256 bytes, PhantFunc 0
ExtTag- RBE+
DevCtl: Report errors: Correctable- Non-Fatal- Fatal-
Unsupported-
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr-
TransPend+
LnkCap: Port #1, Speed 5GT/s, Width x2, ASPM L0s L1,
Exit Latency L0s <64ns, L1 <2us
ClockPM- Surprise- LLActRep- BwNot+ ASPMOptComp+
LnkCtl: ASPM L1 Enabled; RCB 128 bytes Disabled- CommClk
+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 5GT/s, Width x1, TrErr- Train- SlotClk+
DLActive- BWMgmt- ABWMgmt-
SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug-
Surprise-
Slot #0, PowerLimit 0.000W; Interlock- NoCompl+
SltCtl: Enable: AttnBtn- PwrFlt- MRL- PresDet- CmdCplt-
HPIrq- LinkChg-
Control: AttnInd Unknown, PwrInd Unknown, Power-
Interlock-
SltSta: Status: AttnBtn- PowerFlt- MRL- CmdCplt-
PresDet- Interlock-
Changed: MRL- PresDet- LinkState-
RootCtl: ErrCorrectable- ErrNon-Fatal- ErrFatal-
PMEIntEna+ CRSVisible-
RootCap: CRSVisible-
RootSta: PME ReqID 0000, PMEStatus- PMEPending-
DevCap2: Completion Timeout: Not Supported, TimeoutDis-,
LTR+, OBFF Not Supported ARIFwd-
DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-,
LTR-, OBFF Disabled ARIFwd-
LnkCtl2: Target Link Speed: 5GT/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: [100 v1] Virtual Channel
Caps: LPEVC=0 RefClk=100ns PATEntryBits=1
Arb: Fixed- WRR32- WRR64- WRR128-
Ctrl: ArbSelect=Fixed
Status: InProgress-
VC0: Caps: PATOffset=00 MaxTimeSlots=1
RejSnoopTrans-
Arb: Fixed- WRR32- WRR64- WRR128- TWRR128-
WRR256-
Ctrl: Enable+ ID=0 ArbSelect=Fixed TC/VC=ff
Status: NegoPending- InProgress-
Capabilities: [400 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1
+ L1_PM_Substates+
PortCommonModeRestoreTime=30us
PortTPowerOnTime=10us
Capabilities: [600 v1] Latency Tolerance Reporting
Max snoop latency: 0ns
Max no snoop latency: 0ns
Kernel driver in use: pcieport

01:00.0 Class 0200: Device 8086:1521 (rev 01)
Subsystem: Device 1d1a: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-
Latency: 0, Cache Line Size: 128 bytes
Interrupt: pin A routed to IRQ 260
Region 0: Memory at 20000000 (32-bit, non-prefetchable)
[size=1M]
Region 3: Memory at 20600000 (32-bit, non-prefetchable)
[size=16K]
[virtual] Expansion ROM at 20400000 [disabled] [size=512K]
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=1 PME-
Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
Address: 0000000000000000 Data: 0000
Masking: 00000000 Pending: 00000000
Capabilities: [70] MSI-X: Enable+ Count=10 Masked-
Vector table: BAR=3 offset=00000000
PBA: BAR=3 offset=00002000
Capabilities: [a0] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s
<512ns, L1 <64us
ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset+
DevCtl: Report errors: Correctable+ Non-Fatal+ Fatal+
Unsupported+
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
FLReset-
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr+ UncorrErr- FatalErr- UnsuppReq+ AuxPwr+
TransPend-
LnkCap: Port #1, Speed 5GT/s, Width x4, ASPM L0s L1,
Exit Latency L0s <4us, L1 <32us
ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+
LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled-
CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 5GT/s, Width x1, 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: 5GT/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: [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: [140 v1] Device Serial Number
2c-53-4a-ff-ff-03-46-80
Capabilities: [150 v1] Alternative Routing-ID Interpretation
(ARI)
ARICap: MFVC- ACS-, Next Function: 1
ARICtl: MFVC- ACS-, Function Group: 0
Capabilities: [160 v1] Single Root I/O Virtualization (SR-IOV)
IOVCap: Migration-, Interrupt Message Number: 000
IOVCtl: Enable- Migration- Interrupt- MSE- ARIHierarchy-
IOVSta: Migration-
Initial VFs: 8, Total VFs: 8, Number of VFs: 0, Function
Dependency Link: 00
VF offset: 384, stride: 4, Device ID: 1520
Supported Page Size: 00000553, System Page Size:
00000001
VF Migration: offset: 00000000, BIR: 0
Capabilities: [1a0 v1] Transaction Processing Hints
Device specific mode supported
Steering table in TPH capability structure
Capabilities: [1c0 v1] Latency Tolerance Reporting
Max snoop latency: 0ns
Max no snoop latency: 0ns
Capabilities: [1d0 v1] Access Control Services
ACSCap: SrcValid- TransBlk- ReqRedir- CmpltRedir-
UpstreamFwd- EgressCtrl- DirectTrans-
ACSCtl: SrcValid- TransBlk- ReqRedir- CmpltRedir-
UpstreamFwd- EgressCtrl- DirectTrans-
Kernel driver in use: igb

01:00.1 Class 0200: Device 8086:1521 (rev 01)
Subsystem: Device 1d1a: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-
Latency: 0, Cache Line Size: 128 bytes
Interrupt: pin B routed to IRQ 261
Region 0: Memory at 20100000 (32-bit, non-prefetchable)
[size=1M]
Region 3: Memory at 20604000 (32-bit, non-prefetchable)
[size=16K]
[virtual] Expansion ROM at 20480000 [disabled] [size=512K]
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=1 PME-
Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
Address: 0000000000000000 Data: 0000
Masking: 00000000 Pending: 00000000
Capabilities: [70] MSI-X: Enable+ Count=10 Masked-
Vector table: BAR=3 offset=00000000
PBA: BAR=3 offset=00002000
Capabilities: [a0] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s
<512ns, L1 <64us
ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset+
DevCtl: Report errors: Correctable+ Non-Fatal+ Fatal+
Unsupported+
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
FLReset-
MaxPayload 128 bytes, MaxReadReq 512 bytes
DevSta: CorrErr+ UncorrErr- FatalErr- UnsuppReq+ AuxPwr+
TransPend-
LnkCap: Port #1, Speed 5GT/s, Width x4, ASPM L0s L1,
Exit Latency L0s <4us, L1 <32us
ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+
LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled-
CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 5GT/s, Width x1, 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
LnkSta2: Current De-emphasis Level: -6dB,
EqualizationComplete-, EqualizationPhase1-
EqualizationPhase2-, EqualizationPhase3-,
LinkEqualizationRequest-
Capabilities: [100 v2] Advanced Error Reporting
......
......

> > Signed-off-by: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>
> > ---
> > drivers/pci/pcie/portdrv_pci.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> > index eef22dc..86926ea 100644
> > --- a/drivers/pci/pcie/portdrv_pci.c
> > +++ b/drivers/pci/pcie/portdrv_pci.c
> > @@ -179,7 +179,7 @@ static void pcie_portdrv_err_resume(struct pci_dev *dev)
> > */
> > static const struct pci_device_id port_pci_ids[] = { {
> > /* handle any PCI-Express port */
> > - PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0),
> > + PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0x01),
> > }, { /* end: all zeroes */ }
> > };
> >
> > --
> > 2.6.4
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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