Re: [PATCH] PCI: qcom: Disable power management for uPD720201 USB3 controller

[Stanimir Varbanov <svarbanov@mm-sol.com>]

On 6/17/20 12:17 AM, Bjorn Helgaas wrote:
> [+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?

I also think that the USB controller might have some issue with .resume.
It is obvious that qcom-pcie RC doesn't implement suspend/resume which
means that its clocks are not disabled at the moment when USB is resuming.

Georgi, can you try to bypass suspend/resume in the USB driver itself?

> 
> 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().

Yes, definitely we did not implemented suspend/resume callbacks, but
that means that the RC should be functional while the system is in suspend.

> 
>> 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,

-- 
regards,
Stan