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

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Date:   Fri, 20 Apr 2018 10:07:02 -0700
From:   Ravi Chandra Sadineni <ravisadineni@...gle.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        gregkh@...uxfoundation.org, martin.blumenstingl@...glemail.com,
        chunfeng.yun@...iatek.com, johan@...nel.org,
        arvind.yadav.cs@...il.com, Dmitry Torokhov <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,
        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 V2] USB: Increment wakeup count on remote wakeup.

On Fri, Apr 20, 2018 at 7:12 AM, Alan Stern <stern@...land.harvard.edu> wrote:
> 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.

Added the check in V3.  Thanks.
>
> 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))
>>
>

Thanks,
Ravi