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 <20180420180821.194380-1-ravisadineni@chromium.org> <20180421085956.GA8081@kroah.com>
From:   Ravi Chandra Sadineni <ravisadineni@google.com>
Date:   Sat, 21 Apr 2018 06:37:46 -0700
Message-ID: <CAOGSYL00=h-1x=jWuYQ8ucuOE79KN-17L-cCt8Tf1nCNioQxwA@mail.gmail.com>
Subject: Re: [PATCH V5] USB: Increment wakeup count on remote wakeup.
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Ravi Chandra Sadineni <ravisadineni@chromium.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        chunfeng.yun@mediatek.com, johan@kernel.org,
        Arvind Yadav <arvind.yadav.cs@gmail.com>,
        Dmitry Torokhov <dtor@google.com>,
        Anton Bondarenko <anton.bondarenko.sama@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        mathias.nyman@linux.intel.com, felipe.balbi@linux.intel.com,
        Eugene Korenevsky <ekorenevsky@gmail.com>, peter.chen@nxp.com,
        joe@perches.com, Todd Broch <tbroch@google.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Rajat Jain <rajatja@google.com>,
        Benson Leung <bleung@google.com>
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Sure. Pushing it to the older kernels will definitely help.

Thanks,
Ravi

On Sat, Apr 21, 2018 at 1:59 AM, Greg KH <gregkh@linuxfoundation.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@chromium.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