Re: [PATCH V5] USB: Increment wakeup count on remote wakeup.
From: Alan Stern
Date: Fri Apr 20 2018 - 14:22:56 EST
On Fri, 20 Apr 2018, 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 18.104.22.168).
> The upstream facing port then sets C_PORT_SUSPEND bit and reports a
> port change event (USB 2.0 spec section 22.214.171.124.2.3). 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 126.96.36.199) Thus on receiving the Function Wake, increment the
> wakeup count.
> Signed-off-by: Ravi Chandra Sadineni <ravisadineni@xxxxxxxxxxxx>
> 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.
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>