linux-kernel - Re: [PATCH 2/5] PM / Wakeirq: Add automated device wake IRQ handling

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Message-ID: <20150514155455.GE24269@saruman.tx.rr.com>
Date:	Thu, 14 May 2015 10:54:55 -0500
From:	Felipe Balbi <balbi@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Felipe Balbi <balbi@...com>, Tony Lindgren <tony@...mide.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Andreas Fenkart <afenkart@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Huiquan Zhong <huiquan.zhong@...el.com>,
	Kevin Hilman <khilman@...nel.org>, NeilBrown <neilb@...e.de>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Nishanth Menon <nm@...com>,
	Peter Hurley <peter@...leysoftware.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-serial@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 2/5] PM / Wakeirq: Add automated device wake IRQ handling

On Thu, May 14, 2015 at 11:51:10AM -0400, Alan Stern wrote:
> On Wed, 13 May 2015, Felipe Balbi wrote:
> 
> > This brings up a question, actually. What to do with devices which were
> > already runtime suspended when user initiated suspend-to-ram ? Do we
> > leave wakeups enabled, or do we revisit device_may_wakeup() and
> > conditionally runtime_resume the device, disable wakeup, and let its
> > ->suspend() callback be called ?
> 
> In theory, the subsystem/device drivers already have code do this.  
> They're supposed to, anyway.  The USB host stack does it in
> drivers/usb/core/driver.c:choose_wakeup().

that answers the question, specifically, this comment and piece of code
do:

1395 static void choose_wakeup(struct usb_device *udev, pm_message_t msg)
1396 {

[...]

1409         /* Enable remote wakeup if it is allowed, even if no interface drivers
1410          * actually want it.
1411          */
1412         w = device_may_wakeup(&udev->dev);
1413 
1414         /* If the device is autosuspended with the wrong wakeup setting,
1415          * autoresume now so the setting can be changed.
1416          */
1417         if (udev->state == USB_STATE_SUSPENDED && w != udev->do_remote_wakeup)
1418                 pm_runtime_resume(&udev->dev);
1419         udev->do_remote_wakeup = w;
1420 }

so that's something that also needs to be taken into consideration.

Thanks

-- 
balbi

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