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

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Date:   Thu, 4 Aug 2022 09:35:16 +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 Wed, Aug 03, 2022 at 02:58:33PM -0700, Matthias Kaehlcke wrote:
> On Tue, Aug 02, 2022 at 05:14:00PM +0200, Johan Hovold wrote:
> > A device must enable wakeups during runtime suspend regardless of
> > whether it is capable and allowed to wake the system up from system
> > suspend.
> > 
> > Fixes: 2664deb09306 ("usb: dwc3: qcom: Honor wakeup enabled/disabled state")
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> 
> Ah, I wasn't aware that the same wakeup mechanism is used in runtime suspend.
> 
> In how far is runtime PM actually supported/used by this driver? The device is
> set 'active' in _probe(), and there are no other pm_runtime_* calls, except
> in dwc3_qcom_remove() and qcom_dwc3_resume_irq(). How does the device get from
> 'active' into 'suspended'?

It will be runtime suspended when the child (core) device suspends, but
you need to enable runtime PM through sysfs first.

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.

Johan