Re: [PATCH 1/2] usb: dwc3: Don't reinitialize core during host bus-suspend/resume

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Hi,

On 13 July 2017 at 15:26, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
>
>
> On 7/13/2017 11:33 AM, Baolin Wang wrote:
>> On 12 July 2017 at 16:58, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
>>>
>>> On 7/12/2017 2:06 PM, Baolin Wang wrote:
>>>> Hi,
>>>>
>>>> On 12 July 2017 at 15:25, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
>>>>>
>>>>> On 7/12/2017 12:19 PM, Baolin Wang wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On 3 July 2017 at 19:25, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
>>>>>>> Driver powers-off PHYs and reinitializes DWC3 core and gadget on
>>>>>>> resume. While this works fine for gadget mode but in host
>>>>>>> mode there is not re-initialization of host stack. Also, resetting
>>>>>>> bus as part of bus_suspend/resume is not correct which could affect
>>>>>>> (or disconnect) connected devices.
>>>>>>> Fix this by not reinitializing core on suspend/resume in host mode
>>>>>>> for HOST only and OTG/drd configurations.
>>>>>> But for some mobile devices, they also need suspend/resume in host
>>>>>> mode which will power off dwc3 controller in glue layer. If we remove
>>>>>> dwc3_core_init() for host mode, I am afraid it can not work well in
>>>>>> host mode after resuming dwc3.
>>>>> Can you point me to a glue driver doing that?
>>>> Yes, now there are no glue driver doing that, but for many vendor
>>>> trees they will do that. (Our platform will power off dwc3 when
>>>> suspending dwc3, but have not upstreamed yet)
>>>
>>> Fine, but glue driver still need to take care of re-initialization on resume
>>> with current design.
>> Yes.
>>
>>>>> If dwc3 is powered off on suspend then Xhci level initialization also
>>>>> needed
>>>>> after
>>>>> performing dwc3_core_init on resume which is currently not present. So
>>>>> this
>>>>> seems
>>>>> to me broken anyway.
>>>> Since we've add runtime PM for xhci-plat driver [1], which means we
>>>> can runtime suspend/resume xhci device from dwc3 [2].
>>>> [1] https://www.spinics.net/lists/linux-usb/msg156077.html
>>>> [2] https://patchwork.kernel.org/patch/9471869/
>>>
>>> Sure. We can discuss this patch once you re-submit.
>>> One concern I have with the patch is marking ignore_children for dwc3 and as
>>> part of
>>> dwc3 suspend/resume invoking
>> Suppose we will suspend xhci device as dwc3's child, but now dwc3
>> device is not suspend yet, which will block to suspend xhci device.
>> Thus we should set ignore children flag to remove the parent
>> dependency.
>
> I may not have understood the issue. In any case children must be suspended first.
> Example sequence is:
> external hub/device (if any) suspend -> root hub  -> xhci -> dwc3 core -> dwc3 glue.
> xhci device's runtime/pm suspend should happen before dwc3 gets suspended.

Since the [2] patch will get/put xhci usage counter to avoid affecting
other controller's runtime PM, then we need ignore child. But now
xhci-plat driver has done this (by issuing pm_runtime_forbid()
default), we can remove the get/put counter in dwc3, then we do not
need ignore child flag any more.

>>> runtime pm on xhci. Ideally pm core should handle it seamlessly i.e.
>>> suspending dwc3
>>> once xhci gets suspended and pm_stay_awake/relax can be used to block
>>> pm_suspend
>>> until runtime suspend of glue driver happens.
>>>
>>>> But [2] has not applied yet now, I will try to upstream it again. Then
>>>> we can suspend xhci device--> suspend dwc3 host---> glue layer can
>>>> power off, and it is similar when resuming in host mode.
>>>
>>> Do you see any issues with this patch?
>>> I am able to get runtime suspend/resume happening fine with XHCI on my
>>> platform.
>>> It involves runtime suspend/resume of USB HUB and dwc3 glue driver without
>>> any other
>>> change.
>> Great, I will try this patch again.
>>
>



-- 
Baolin.wang
Best Regards
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