linux-kernel - Re: [PATCH V2] USB: Increment wakeup count on remote wakeup.

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Date:   Fri, 20 Apr 2018 10:12:52 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Ravi Chandra Sadineni <ravisadineni@...omium.org>
cc:     gregkh@...uxfoundation.org, <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 V2] USB: Increment wakeup count on remote wakeup.

On Thu, 19 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 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>
> ---
>  drivers/usb/core/hcd.c |  2 ++
>  drivers/usb/core/hub.c | 10 +++++++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 777036ae63674..ee0f3ec57ce49 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -2374,7 +2374,9 @@ static void hcd_resume_work(struct work_struct *work)
>  void usb_hcd_resume_root_hub (struct usb_hcd *hcd)
>  {
>  	unsigned long flags;
> +	struct device *dev = &hcd->self.root_hub->dev;
>  
> +	pm_wakeup_event(dev, 0);
>  	spin_lock_irqsave (&hcd_root_hub_lock, flags);
>  	if (hcd->rh_registered) {
>  		set_bit(HCD_FLAG_WAKEUP_PENDING, &hcd->flags);

In general, hcd->self.root_hub is guaranteed to be non-NULL only when 
hcd->rh_registered is set.  Therefore the assignment to dev and the 
call to pm_wakeup_event() should be moved within this "if" statement.

The rest of the patch looks okay.

Alan Stern

> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index f6ea16e9f6bb9..aa9968d90a48c 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -653,12 +653,17 @@ void usb_wakeup_notification(struct usb_device *hdev,
>  		unsigned int portnum)
>  {
>  	struct usb_hub *hub;
> +	struct usb_port *port_dev;
>  
>  	if (!hdev)
>  		return;
>  
>  	hub = usb_hub_to_struct_hub(hdev);
>  	if (hub) {
> +		port_dev = hub->ports[portnum - 1];
> +		if (port_dev && port_dev->child)
> +			pm_wakeup_event(&port_dev->child->dev, 0);
> +
>  		set_bit(portnum, hub->wakeup_bits);
>  		kick_hub_wq(hub);
>  	}
> @@ -3434,8 +3439,11 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>  
>  	/* Skip the initial Clear-Suspend step for a remote wakeup */
>  	status = hub_port_status(hub, port1, &portstatus, &portchange);
> -	if (status == 0 && !port_is_suspended(hub, portstatus))
> +	if (status == 0 && !port_is_suspended(hub, portstatus)) {
> +		if (portchange & USB_PORT_STAT_C_SUSPEND)
> +			pm_wakeup_event(&udev->dev, 0);
>  		goto SuspendCleared;
> +	}
>  
>  	/* see 7.1.7.7; affects power usage, but not budgeting */
>  	if (hub_is_superspeed(hub->hdev))
>