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Date:   Tue, 16 Jun 2020 16:17:11 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Georgi Djakov <georgi.djakov@linaro.org>
Cc:     svarbanov@mm-sol.com, bjorn.andersson@linaro.org, vkoul@kernel.org,
        sanm@codeaurora.org, mgautam@codeaurora.org, agross@kernel.org,
        bhelgaas@google.com, robh@kernel.org, lorenzo.pieralisi@arm.com,
        linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, linux-pm@vger.kernel.org
Subject: Re: [PATCH] PCI: qcom: Disable power management for uPD720201 USB3
 controller
Message-ID: <20200616211711.GA1981914@bjorn-Precision-5520>
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[+cc Rafael, linux-pm]

On Mon, Jun 15, 2020 at 09:24:13PM +0300, Georgi Djakov wrote:
> The uPD720201 USB3 host controller (connected to PCIe) on the Dragonboard
> 845c is often failing during suspend and resume. The following messages
> are seen over the console:
> 
>   PM: suspend entry (s2idle)
>   Filesystems sync: 0.000 seconds
>   Freezing user space processes ... (elapsed 0.001 seconds) done.
>   OOM killer disabled.
>   Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
>   printk: Suspending console(s) (use no_console_suspend to debug)
>   dwc3-qcom a8f8800.usb: HS-PHY not in L2
>   dwc3-qcom a6f8800.usb: HS-PHY not in L2
>   xhci_hcd 0000:01:00.0: can't change power state from D3hot to D0 (config
>   space inaccessible)
>   xhci_hcd 0000:01:00.0: can't change power state from D3hot to D0 (config
>   space inaccessible)
>   xhci_hcd 0000:01:00.0: Controller not ready at resume -19
>   xhci_hcd 0000:01:00.0: PCI post-resume error -19!
>   xhci_hcd 0000:01:00.0: HC died; cleaning up
> 
> Then the USB devices are not functional anymore. Let's disable the PM of
> the controller for now, as this will at least keep USB devices working
> even after suspend and resume.

This seems like we're just covering up a deeper problem here.  I think
it would be better to fix the underlying problem.

The quirk you're adding is specific to the Renesas 0x0014 device.  Is
there some reason to think the problem is specific to that device, or
might other devices have the same problem?

Maybe we're missing something in pcie-qcom.c?  Is there any
suspend/resume support required in that driver?  It doesn't look like
it has anything except that it calls pm_runtime_enable().

> Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 138e1a2d21cc..c1f502682a19 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1439,6 +1439,13 @@ static void qcom_fixup_class(struct pci_dev *dev)
>  {
>  	dev->class = PCI_CLASS_BRIDGE_PCI << 8;
>  }
> +
> +static void qcom_fixup_nopm(struct pci_dev *dev)
> +{
> +	dev->pm_cap = 0;
> +	dev_info(&dev->dev, "Disabling PCI power management\n");
> +}
> +
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0101, qcom_fixup_class);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0104, qcom_fixup_class);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0106, qcom_fixup_class);
> @@ -1446,6 +1453,7 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0107, qcom_fixup_class);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x0302, qcom_fixup_class);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1000, qcom_fixup_class);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_QCOM, 0x1001, qcom_fixup_class);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_RENESAS, 0x0014, qcom_fixup_nopm);

The convention is that DECLARE_PCI_FIXUP_*() comes immediately after
the quirk function itself, so the whole patch would be a single diff
hunk.  See drivers/pci/quirks.c for many examples.

>  static struct platform_driver qcom_pcie_driver = {
>  	.probe = qcom_pcie_probe,