linux-kernel - Re: [PATCH v2] usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't probed properly

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Date:   Sat, 16 Jul 2022 09:43:27 +0530
From:   Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To:     Matthias Kaehlcke <mka@...omium.org>
CC:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Felipe Balbi <balbi@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        <linux-arm-msm@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Pavan Kondeti <quic_pkondeti@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH v2] usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't
 probed properly


On 7/16/2022 2:11 AM, Matthias Kaehlcke wrote:
> On Fri, Jul 15, 2022 at 06:51:52PM +0530, Krishna Kurapati wrote:
>
>> Subject: usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't probed properly
> nit: "isn't probed properly" sounds like a bug or HW issue. In case
> you re-spin maybe change it to "hasn't probed yet" or similar.
>
>> On SC7180 devices, it is observed that dwc3 probing is deferred
>> because device_links_check_suppliers() finds that '88e3000.phy'
>> isn't ready yet.
>>
>> As a part of its probe call, dwc3-qcom driver checks if dwc3 core
>> is wakeup capable or not. If the dwc3 core is wakeup capable, driver
>> configures dwc-qcom's power domain to be always ON. Also it configures
>> dp/dm interrupts accordingly to support wakeup from system suspend.
>>
>> More info regarding the same can be found at:
>> commit d9be8d5c5b03 ("usb: dwc3: qcom: Keep power domain on to retain controller status")
>> commit 6895ea55c385 ("usb: dwc3: qcom: Configure wakeup interrupts during suspend")
>>
>> In the event, dwc3 probe gets deferred and is processed after dwc3-qcom
>> probe, driver ends up reading the wakeup capability of dwc3 core as false
>> leading to instability in suspend/resume path.
>>
>> To avoid this scenario, ensure dwc3_probe is successful by checking
>> if appropriate driver is assigned to it or not after the of_platform_populate
>> call. If it isn't then defer dwc3-qcom probe as well.
>>
>> Fixes: 649f5c842ba3 ("usb: dwc3: core: Host wake up support from system suspend")
>> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> Reported-by: Matthias Kaehlcke <mka@...omium.org>
> Tested-by: Matthias Kaehlcke <mka@...omium.org>
> Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
>
> Please make sure to add reviewers of previous versions or other folks you
> would like to review your patches in cc. I found v2 accidentally while
> looking for something else.
Hi Mathias,
     Sure, Thanks for the review.