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From: Rajat Jain <rajatja@google.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Ravi Chandra Sadineni <ravisadineni@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	martin.blumenstingl@googlemail.com,
	Ravi Chandra Sadineni <ravisadineni@google.com>,
	chunfeng.yun@mediatek.com, johan@kernel.org,
	arvind.yadav.cs@gmail.com, Dmitry Torokhov <dtor@google.com>,
	anton.bondarenko.sama@gmail.com, f.fainelli@gmail.com,
	keescook@chromium.org, mathias.nyman@linux.intel.com,
	felipe.balbi@linux.intel.com, ekorenevsky@gmail.com,
	peter.chen@nxp.com, joe@perches.com,
	Todd Broch <tbroch@google.com>,
	linux-usb@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Benson Leung <bleung@google.com>
Subject: Re: [PATCH] USB: Increment wakeup count on remote wakeup.
Date: Thu, 19 Apr 2018 09:17:40 -0700	[thread overview]
Message-ID: <CACK8Z6Gq4R7nKJA-Jmichv5VyBWhF=RdYVBiGsmeg0VUjrMnFA@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1804191053410.1288-100000@iolanthe.rowland.org>

On Thu, Apr 19, 2018 at 8:01 AM, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Wed, 18 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: ravisadineni@chromium.org
>> ---
>>  drivers/usb/core/hcd.c |  1 +
>>  drivers/usb/core/hub.c | 12 ++++++++++--
>>  2 files changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 777036ae63674..79f95a878fb6e 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
>> @@ -2375,6 +2375,7 @@ void usb_hcd_resume_root_hub (struct usb_hcd *hcd)
>>  {
>>       unsigned long flags;
>>
>> +     pm_wakeup_event(dev, 0);
>
> Instead of dev, you probably want to use hcd->self.sysdev.  Or maybe
> hcd->self.controller, although the difference probably doesn't matter
> for your purposes.
>
> On the other hand, this wakeup event may already have been counted by
> the host controller's bus subsystem.  Does it matter if the same wakeup
> event gets counted twice?

No. The context is that we're interested in making user space behave
differently if the wake up source was a user input device (e.g. USB
keyboard) v/s some other kind of USB device. So all that matters is
that the USB device wakeup count gets incremented.

>
> (This is inevitable with USB devices, in any case.  If a device sends a
> wakeup request, it will be counted for that device, for all the
> intermediate hubs, and for the host controller.)
>
>> @@ -3432,10 +3437,13 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>>
>>       usb_lock_port(port_dev);
>>
>> -     /* 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))
>> +     /* Skip the initial Clear-Suspend step for a remote wakeup */
>
> What is the reason for moving the comment line down after the
> hub_port_status() call?
>
> Alan Stern
>
>> +     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))
>>
>

  reply	other threads:[~2018-04-19 16:18 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19  0:18 Ravi Chandra Sadineni
2018-04-19  9:30 ` kbuild test robot
2018-04-19  9:33 ` kbuild test robot
2018-04-19 15:01 ` Alan Stern
2018-04-19 16:17   ` Rajat Jain [this message]
2018-04-20  0:27   ` [PATCH V2] " Ravi Chandra Sadineni
2018-04-20 14:12     ` Alan Stern
2018-04-20 17:05       ` [PATCH V3] " Ravi Chandra Sadineni
2018-04-20 17:29         ` Alan Stern
2018-04-20 17:54           ` [PATCH V4] " Ravi Chandra Sadineni
2018-04-20 18:08           ` [PATCH V5] " Ravi Chandra Sadineni
2018-04-20 18:22             ` Alan Stern
2018-04-21  8:59             ` Greg KH
2018-04-21 13:37               ` Ravi Chandra Sadineni
2018-04-20 18:12           ` [PATCH V3] " Ravi Chandra Sadineni
2018-04-20 17:07       ` [PATCH V2] " Ravi Chandra Sadineni
2018-04-20  0:50   ` [PATCH] " Ravi Chandra Sadineni

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