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Date:   Mon, 16 Jan 2017 12:36:45 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     John Youn <John.Youn@...opsys.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        John Youn <John.Youn@...opsys.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Mark Brown <broonie@...nel.org>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: core: Disable USB2.0 phy suspend when dwc3 acts as host role


Hi,

John Youn <John.Youn@...opsys.com> writes:
>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>>> When dwc3 controller acts as host role with attaching slow speed device
>>>>> (like mouse or keypad). Then if we plugged out the slow speed device,
>>>>> it will timeout to run the deconfiguration endpoint command to drop the
>>>>> endpoint's resources. Some xHCI command timeout log as below when
>>>>> disconnecting one slow device:
>>>>>
>>>>> [   99.807739] c0 xhci-hcd.0.auto: Port Status Change Event for port 1
>>>>> [   99.814699] c0 xhci-hcd.0.auto: resume root hub
>>>>> [   99.819992] c0 xhci-hcd.0.auto: handle_port_status: starting port
>>>>>                                  polling.
>>>>> [   99.827808] c0 xhci-hcd.0.auto: get port status, actual port 0 status
>>>>>                                  = 0x202a0
>>>>> [   99.835903] c0 xhci-hcd.0.auto: Get port status returned 0x10100
>>>>> [   99.850052] c0 xhci-hcd.0.auto: clear port connect change, actual
>>>>>                                  port 0 status  = 0x2a0
>>>>> [   99.859313] c0 xhci-hcd.0.auto: Cancel URB ffffffc01ed6cd00, dev 1,
>>>>>                                  ep 0x81, starting at offset 0xc406d210
>>>>> [   99.869645] c0 xhci-hcd.0.auto: // Ding dong!
>>>>> [   99.874776] c0 xhci-hcd.0.auto: Stopped on Transfer TRB
>>>>> [   99.880713] c0 xhci-hcd.0.auto: Removing canceled TD starting at
>>>>>                                  0xc406d210 (dma).
>>>>> [   99.889012] c0 xhci-hcd.0.auto: Finding endpoint context
>>>>> [   99.895069] c0 xhci-hcd.0.auto: Cycle state = 0x1
>>>>> [   99.900519] c0 xhci-hcd.0.auto: New dequeue segment =
>>>>>                                  ffffffc1112f0880 (virtual)
>>>>> [   99.908655] c0 xhci-hcd.0.auto: New dequeue pointer = 0xc406d220 (DMA)
>>>>> [   99.915927] c0 xhci-hcd.0.auto: Set TR Deq Ptr cmd, new deq seg =
>>>>>                                  ffffffc1112f0880 (0xc406d000 dma),
>>>>>                                  new deq ptr = ffffff8002175220
>>>>>                                  (0xc406d220 dma), new cycle = 1
>>>>> [   99.931242] c0 xhci-hcd.0.auto: // Ding dong!
>>>>> [   99.936360] c0 xhci-hcd.0.auto: Successful Set TR Deq Ptr cmd,
>>>>>                                  deq = @c406d220
>>>>> [   99.944458] c0 xhci-hcd.0.auto: xhci_hub_status_data: stopping port
>>>>>                                  polling.
>>>>> [  100.047619] c0 xhci-hcd.0.auto: xhci_drop_endpoint called for udev
>>>>>                                  ffffffc01ae08800
>>>>> [  100.057002] c0 xhci-hcd.0.auto: drop ep 0x81, slot id 1, new drop
>>>>>                                  flags = 0x8, new add flags = 0x0
>>>>> [  100.067878] c0 xhci-hcd.0.auto: xhci_check_bandwidth called for udev
>>>>>                                  ffffffc01ae08800
>>>>> [  100.076868] c0 xhci-hcd.0.auto: New Input Control Context:
>>>>>
>>>>> ......
>>>>>
>>>>> [  100.427252] c0 xhci-hcd.0.auto: // Ding dong!
>>>>> [  105.430728] c0 xhci-hcd.0.auto: Command timeout
>>>>> [  105.436029] c0 xhci-hcd.0.auto: Abort command ring
>>>>> [  113.558223] c0 xhci-hcd.0.auto: Command completion event does not match
>>>>>                                  command
>>>>> [  113.569778] c0 xhci-hcd.0.auto: Timeout while waiting for configure
>>>>>                                  endpoint command
>>>>>
>>>>> The reason is it will suspend USB phy to disable phy clock when
>>>>> disconnecting the slow USB decice, that will hang on the xHCI commands
>>>>> executing which depends on the phy clock.
>>>>>
>>>>> Thus we should disable USB2.0 phy suspend feature when dwc3 acts as host
>>>>> role.
>>>>>
>>>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>>>> ---
>>>>>  drivers/usb/dwc3/core.c |   14 ++++++++++++++
>>>>>  1 file changed, 14 insertions(+)
>>>>>
>>>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>>>> index 9a4a5e4..0b646cf 100644
>>>>> --- a/drivers/usb/dwc3/core.c
>>>>> +++ b/drivers/usb/dwc3/core.c
>>>>> @@ -565,6 +565,20 @@ static int dwc3_phy_setup(struct dwc3 *dwc)
>>>>>       if (dwc->revision > DWC3_REVISION_194A)
>>>>>               reg |= DWC3_GUSB2PHYCFG_SUSPHY;
>>>>>
>>>>> +     /*
>>>>> +      * When dwc3 controller acts as host role with attaching one slow speed
>>>>> +      * device (like mouse or keypad). Then if we plugged out the slow speed
>>>>> +      * device, it will timeout to run the deconfiguration endpoint command.
>>>>> +      * The reason is it will suspend USB phy to disable phy clock when
>>>>> +      * disconnecting slow speed decice, which will affect the xHCI commands
>>>>> +      * executing.
>>>>> +      *
>>>>> +      * Thus we should disable USB 2.0 phy suspend feature when dwc3 acts as
>>>>> +      * host role.
>>>>> +      */
>>>>> +     if (dwc->dr_mode == USB_DR_MODE_HOST || dwc->dr_mode == USB_DR_MODE_OTG)
>>>>> +             reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
>>>>
>>>> which version of the core you're using? Recent version (since 1.94A,
>>>
>>> My version is 2.80a.
>>>
>>>> IIRC) can manage core suspend automatically. Also, this patch of yours
>>>> will cause a power consumption regression.
>>>
>>> Yes, it can manage core suspend automatically, that is the problem.
>>> When plugging out one mouse or keypad device, the phy will suspend
>>> automatically to disable the phy clock. But now the disconnecting
>>> process is not finished, and some xHCI commands (like deconfiguration
>>> endpoint command to drop endpoint resources) need depend on the phy
>>> clock, which will hang on the system to timeout the command or abort
>>> command ring to halt the xHCI.
>>>
>>> I agree with you it will cause a power consumption regression, but it
>>> will cause serious problem if not. Do you have some suggestion?
>> 
>> sorry for the long delay. This was lost in my inbox.
>> 
>> I'm not sure this patch is the best solution. There's no mention in
>> Databook that we should avoid PHY suspend when acting as host. Adding
>> John here to see if John has any idea of how to fix this.
>> 
>
> I'm not familiar enough with XHCI side of things to say.
>
> I'll ask around to see if anyone has an idea.

Thank you

-- 
balbi

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