linux-kernel - Re: [PATCH V5] USB: Increment wakeup count on remote wakeup.

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Date:   Sat, 21 Apr 2018 06:37:46 -0700
From:   Ravi Chandra Sadineni <ravisadineni@...gle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        chunfeng.yun@...iatek.com, johan@...nel.org,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Dmitry Torokhov <dtor@...gle.com>,
        Anton Bondarenko <anton.bondarenko.sama@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Kees Cook <keescook@...omium.org>,
        mathias.nyman@...ux.intel.com, felipe.balbi@...ux.intel.com,
        Eugene Korenevsky <ekorenevsky@...il.com>, peter.chen@....com,
        joe@...ches.com, Todd Broch <tbroch@...gle.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rajat Jain <rajatja@...gle.com>,
        Benson Leung <bleung@...gle.com>
Subject: Re: [PATCH V5] USB: Increment wakeup count on remote wakeup.

Sure. Pushing it to the older kernels will definitely help.

Thanks,
Ravi

On Sat, Apr 21, 2018 at 1:59 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Fri, Apr 20, 2018 at 11:08:21AM -0700, Ravi Chandra Sadineni wrote:
>> On chromebooks we depend on wakeup count to identify the wakeup source.
>> But currently USB devices do not increment the wakeup count when they
>> trigger the remote wake. This patch addresses the same.
>>
>> Resume condition is reported differently on USB 2.0 and USB 3.0 devices.
>>
>> On USB 2.0 devices, a wake capable device, if wake enabled, drives
>> resume signal to indicate a remote wake (USB 2.0 spec section 7.1.7.7).
>> The upstream facing port then sets C_PORT_SUSPEND bit and reports a
>> port change event (USB 2.0 spec section 11.24.2.7.2.3). Thus if a port
>> has resumed before driving the resume signal from the host and
>> C_PORT_SUSPEND is set, then the device attached to the given port might
>> be the reason for the last system wakeup. Increment the wakeup count for
>> the same.
>>
>> On USB 3.0 devices, a function may signal that it wants to exit from device
>> suspend by sending a Function Wake Device Notification to the host (USB3.0
>> spec section 8.5.6.4) Thus on receiving the Function Wake, increment the
>> wakeup count.
>>
>> Signed-off-by: Ravi Chandra Sadineni <ravisadineni@...omium.org>
>> ---
>>
>> V5: Added the description of changes between different versions of patches.
>> V4: Moved the wakeup count increment logic to the existing if which is
>> safegaurded by hcd_root_hub_lock spinlock.
>> V3: Added a gaurd to check if rh_registered is set before accessing
>> root_hub pointer.
>> V2: Fixed the build failure error due to uninitialized dev pointer.
>
> Is this needed in older kernels?  Should I submit it to the stable
> trees?
>
> thanks,
>
> greg k-h