linux-kernel - Re: [PATCH 4/8] usb: dwc3: qcom: fix runtime PM wakeup

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Message-ID: <YuvuJR0ZqSvwMSi1@hovoldconsulting.com>
Date:   Thu, 4 Aug 2022 18:04:53 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Doug Anderson <dianders@...omium.org>,
        Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        quic_ppratap@...cinc.com, quic_vpulyala@...cinc.com,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] usb: dwc3: qcom: fix runtime PM wakeup

On Thu, Aug 04, 2022 at 08:35:10AM -0700, Matthias Kaehlcke wrote:
> On Thu, Aug 04, 2022 at 09:35:16AM +0200, Johan Hovold wrote:

> After enabling runtime suspend for the dwc3 core, dwc3 glue and the xHCI
> the dwc3-qcom enters autosuspend when the delay expires.
> 
> > And the controller is resumed in the wakeup-interrupt handler for the
> > runtime PM case.
> >
> > It seems to work ok, and it looks like the driver has supported this
> > since it was first merged.
> 
> With and without your patch dwc3-qcom enters autosuspend and stays there.
> USB devices like a mouse or a USB to Ethernet adapter keep working while
> the glue is suspended.

Are you sure you're looking at the right controller? And that it is
actually suspended?

If you plug in a keyboard, enable autosuspend for all devices in the
path (from glue to the keyboard device) and type away, then the
controller must remain active. Stop typing, and all devices in the chain
should suspend.

> How is the runtime resume triggered for the dwc3 glue?

Either by the host driver when it needs to access the device, or by the
device if it is remote-wakeup capable (e.g. a keyboard, but not
necessarily a speaker).

Note that the latter part is what is broken currently as the wakeup
interrupts were not enabled and those are needed to wake up sc8280xp 
when the dwc3 glue has been runtime suspended.

Johan