linux-kernel - Re: [PATCH] x86/PCI: Remove D0 PME capability on AMD FCH xHCI

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Date:   Wed, 2 Oct 2019 13:32:07 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH] x86/PCI: Remove D0 PME capability on AMD FCH xHCI



> On Oct 2, 2019, at 08:07, Bjorn Helgaas <helgaas@...nel.org> wrote:
> 
> [+cc Alan, Mathias, Rafael, Lukas]
> 
> On Mon, Sep 02, 2019 at 10:52:52PM +0800, Kai-Heng Feng wrote:
>> There's an xHCI device that doesn't wake when a USB 2.0 device gets
>> plugged to its USB 3.0 port. The driver's own runtime suspend callback
>> was called, PME# signaling was enabled, but it stays at PCI D0:
>> 
>> 00:10.0 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] FCH USB XHCI Controller [1022:7914] (rev 20) (prog-if 30 [XHCI])
>>        Subsystem: Dell FCH USB XHCI Controller [1028:087e]
>>        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 18
>>        Region 0: Memory at f0b68000 (64-bit, non-prefetchable) [size=8K]
>>        Capabilities: [50] 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-
>> 
>> A PCI device can be runtime suspended while still stays at D0 when it
>> supports D0 PME# and its ACPI _S0W method reports D0. Though plugging
>> USB 3.0 devices can wakeup the xHCI, it doesn't respond to USB 2.0
>> devices.
> 
> I don't think _S0W and runtime suspend are relevant here.  What *is*
> relevant is that the device advertises that it can generate PME from
> D0, and it apparently does not do so.

Yes that's the case. It doesn't generate PME when USB2.0 or USB1.1 device gets plugged.

> 
> Table 10 in the xHCI spec r1.0, sec 4.15.2.3, says the xHC should
> assert PME# if enabled and the port's WCE bit is set.  Did you ever
> confirm that WCE is set?

How do I check WCE when xHCI is suspended?
If I want to read WCE then I have the resume the device, but after resuming all USB devices get enumerated, and checking WCE doesn't matter anymore.

> 
> I assume WCE *is* set because plugging in a USB3 device *does*
> generate a PME#, and I don't see anything in Table 10 that says it
> would work for USB3 but not USB2.

It should work on all USB speeds, but it didn't.
That's why the OEM/ODM use the _S0W workaround on Windows.

Kai-Heng

> 
>> So let's disable D0 PME capability on this device to avoid the issue.
>> 
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203673
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>> ---
>> arch/x86/pci/fixup.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>> 
>> diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
>> index 527e69b12002..0851a05d092f 100644
>> --- a/arch/x86/pci/fixup.c
>> +++ b/arch/x86/pci/fixup.c
>> @@ -588,6 +588,17 @@ static void pci_fixup_amd_ehci_pme(struct pci_dev *dev)
>> }
>> DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x7808, pci_fixup_amd_ehci_pme);
>> 
>> +/*
>> + * Device [1022:7914]
>> + * D0 PME# doesn't get asserted when plugging USB 2.0 device.
>> + */
>> +static void pci_fixup_amd_fch_xhci_pme(struct pci_dev *dev)
>> +{
>> +	dev_info(&dev->dev, "PME# does not work under D0, disabling it\n");
> 
> Use pci_info() as in the rest of the file.
> 
>> +	dev->pme_support &= ~(PCI_PM_CAP_PME_D0 >> PCI_PM_CAP_PME_SHIFT);
>> +}
>> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, 0x7914, pci_fixup_amd_fch_xhci_pme);
>> +
>> /*
>>  * Apple MacBook Pro: Avoid [mem 0x7fa00000-0x7fbfffff]
>>  *
>> -- 
>> 2.17.1