linux-kernel - Re: [PATCH 2/3] USB: dwc3: qcom: fix wakeup after probe deferral

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Date:   Tue, 21 Nov 2023 14:50:08 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
Cc:     Andrew Halaney <ahalaney@...hat.com>,
        Johan Hovold <johan+linaro@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Wesley Cheng <quic_wcheng@...cinc.com>,
        linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/3] USB: dwc3: qcom: fix wakeup after probe deferral

On Tue, Nov 21, 2023 at 06:25:37PM +0530, Krishna Kurapati PSSNV wrote:

> > Specifically, I consider the current implementation to be broken in that
> > it generates wakeup events on disconnect which is generally not want you
> > want. Consider closing the lid of your laptop and disconnecting a USB
> > mouse before putting it in your backpack. Now it's no longer suspended
> > as you would expect it to be.

>   Just one query. Even if it wakes up after closing the lid and removing 
> the mouse, wouldn't pm suspend be triggered again later by the system 
> once it sees that usb is also good to be suspended again ? I presume a 
> laptop form factor would be having this facility of re-trigerring 
> suspend. Let me know if this is not the case.

No, we generally don't use opportunistic suspend (e.g. unlike android)
so the laptop will not suspend again.

So this is an actual bug affecting, for example, the Lenovo ThinkPad
X13s.

> Also, the warning you are mentioning in [1] comes because this is a 
> laptop form factor and we have some firmware running (I don't know much 
> about ACPI and stuff) ?

No, the "firmware" in this case is just the devicetree which has the
DP/DM interrupts defined as edge-triggered while the driver requests
them as level triggered.

(It would look similar with ACPI firmware which also has these declared
as edge triggered.)

Johan