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Date:   Thu, 4 Aug 2022 08:35:10 -0700
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Johan Hovold <johan@kernel.org>
Cc:     Johan Hovold <johan+linaro@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <balbi@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Krishna Kurapati <quic_kriskura@quicinc.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Doug Anderson <dianders@chromium.org>,
        Pavankumar Kondeti <quic_pkondeti@quicinc.com>,
        quic_ppratap@quicinc.com, quic_vpulyala@quicinc.com,
        linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/8] usb: dwc3: qcom: fix runtime PM wakeup
Message-ID: <YuvnLliIKLK71wx0@google.com>
References: <20220802151404.1797-1-johan+linaro@kernel.org>
 <20220802151404.1797-5-johan+linaro@kernel.org>
 <YurviWfzut9sursr@google.com>
 <Yut2tLqGfu82xcDs@hovoldconsulting.com>
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On Thu, Aug 04, 2022 at 09:35:16AM +0200, Johan Hovold wrote:
> 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@kernel.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.

Thanks for the clarification.

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.

How is the runtime resume triggered for the dwc3 glue?

Sorry if my questions are very basic, so far I haven't dealt much with
autosuspend and I'm trying to get a better understanding in the context
of the dwc3 and why it is currently broken.