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

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Message-ID: <20180421085956.GA8081@kroah.com>
Date:   Sat, 21 Apr 2018 10:59:56 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Ravi Chandra Sadineni <ravisadineni@...omium.org>
Cc:     stern@...land.harvard.edu, martin.blumenstingl@...glemail.com,
        ravisadineni@...gle.com, chunfeng.yun@...iatek.com,
        johan@...nel.org, arvind.yadav.cs@...il.com, dtor@...gle.com,
        anton.bondarenko.sama@...il.com, f.fainelli@...il.com,
        keescook@...omium.org, mathias.nyman@...ux.intel.com,
        felipe.balbi@...ux.intel.com, ekorenevsky@...il.com,
        peter.chen@....com, joe@...ches.com, tbroch@...gle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        rajatja@...gle.com, bleung@...gle.com
Subject: Re: [PATCH V5] USB: Increment wakeup count on remote wakeup.

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