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Message-ID: <fb1398ed-3a75-a0f9-32b2-50c06dd0b55a@quicinc.com>
Date:   Thu, 14 Jul 2022 20:33:28 +0530
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Subject: Re: [PATCH] usb: dwc3: qcom: Defer dwc3-qcom probe if dwc3 isn't
 probed properly
Content-Language: en-US
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Felipe Balbi <balbi@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        <linux-arm-msm@vger.kernel.org>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <1657810516-31143-1-git-send-email-quic_kriskura@quicinc.com>
 <YtAv1U1VYkhIY1GA@kroah.com>
From:   Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>
In-Reply-To: <YtAv1U1VYkhIY1GA@kroah.com>
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On 7/14/2022 8:31 PM, Greg Kroah-Hartman wrote:
> On Thu, Jul 14, 2022 at 08:25:16PM +0530, Krishna Kurapati wrote:
>> 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.
>>
>> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
>> ---
>>   drivers/usb/dwc3/dwc3-qcom.c | 3 +++
>>   1 file changed, 3 insertions(+)
> I got 2 different copies of this change, what's the difference?
>
> confused,
>
> greg k-h
Sorry Greg, My bad, I thought the mail sending failed the first time. So 
I sent the same patch second time. Sorry for the confusion.
Regards,
Krishna,