linux-kernel - Re: boot interrupt quirk (also in 4.19.y) breaks serial ports (was: [PATCH v2 0/2] pci: Add boot interrupt quirk mechanism for Xeon chipsets)

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Message-ID: <87r1obi0hn.fsf@nanos.tec.linutronix.de>
Date:   Mon, 30 Nov 2020 11:48:36 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Stefan Bühler 
        <stefan.buehler@....uni-stuttgart.de>,
        sean.v.kelley@...ux.intel.com
Cc:     bhelgaas@...gle.com, bp@...en8.de, corbet@....net,
        kar.hin.ong@...com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        mingo@...hat.com, sassmann@...nic.de, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: boot interrupt quirk (also in 4.19.y) breaks serial ports (was: [PATCH v2 0/2] pci: Add boot interrupt quirk mechanism for Xeon chipsets)

Stefan,

On Fri, Nov 27 2020 at 10:17, Stefan Bühler wrote:
> On 11/27/20 12:45 AM, Thomas Gleixner wrote:
>> Can you please run this as root so the Capabilities are accessible?
>
> My bad, sorry. I did intend to run it as root, but should have checked
> the output.  Again see attached file.

No problem.

> 05:00.0 PCI bridge: PLX Technology, Inc. PEX8112 x1 Lane PCI Express-to-PCI Bridge (rev aa) (prog-if 00 [Normal decode])
> 	Physical Slot: 1
> 	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: 32 bytes
> 	Interrupt: pin A routed to IRQ 16
> 	NUMA node: 0
> 	Bus: primary=05, secondary=06, subordinate=06, sec-latency=64
> 	I/O behind bridge: 0000e000-0000efff
> 	Memory behind bridge: fb400000-fb4fffff
> 	Prefetchable memory behind bridge: fff00000-000fffff
> 	Secondary status: 66MHz+ FastB2B- ParErr- DEVSEL=medium >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: 0000000000000000  Data: 0000

So the bridge would support MSI, but obviously the devices on the PCI
side do not.

> 06:00.0 Serial controller: Oxford Semiconductor Ltd OX16PCI954 (Quad 16950 UART) function 0 (Uart) (prog-if 06 [16950])
> 	Subsystem: Oxford Semiconductor Ltd OX16PCI954 (Quad 16950 UART) function 0 (Uart)
> 	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
> 	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
> 	Interrupt: pin A routed to IRQ 16
> 	NUMA node: 0
> 	Region 0: I/O ports at e0e0 [size=32]
> 	Region 1: Memory at fb407000 (32-bit, non-prefetchable) [size=4K]
> 	Region 2: I/O ports at e0c0 [size=32]
> 	Region 3: Memory at fb406000 (32-bit, non-prefetchable) [size=4K]
> 	Capabilities: [40] Power Management version 1
> 		Flags: PMEClk- DSI- D1- D2+ AuxCurrent=0mA PME(D0+,D1-,D2+,D3hot+,D3cold-)
> 		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-

But that should still work because the boot interrupt quirk should not
affect interrupts which are routed through the IOAPIC.

Sean, any idea what's going on here?

Thanks,

        tglx