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Date:   Tue, 1 Oct 2019 19:07:18 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alan Stern <stern@rowland.harvard.edu>,
        Mathias Nyman <mathias.nyman@intel.com>,
        Rafael Wysocki <rafael.j.wysocki@intel.com>,
        Lukas Wunner <lukas@wunner.de>
Subject: Re: [PATCH] x86/PCI: Remove D0 PME capability on AMD FCH xHCI
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[+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.

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?

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.

> 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@canonical.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
>