linux-kernel - [PATCH] Revert "USB / PM: Allow USB devices to remain runtime-suspended when sleeping"

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Date:	Mon,  2 May 2016 15:35:57 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	stable@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH] Revert "USB / PM: Allow USB devices to remain runtime-suspended when sleeping"

This reverts commit e3345db85068ddb937fc0ba40dfc39c293dad977, which
broke system resume for a large class of devices.

Devices that after having been reset during resume need to be rebound
due to a missing reset_resume callback, are now left in a suspended
state. This specifically broke resume of common USB-serial devices,
which are now unusable after system suspend (until disconnected and
reconnected) when USB persist is enabled.

During resume, usb_resume_interface will set the needs_binding flag for
such interfaces, but unlike system resume, run-time resume does not
honour it.

Cc: stable <stable@...r.kernel.org>	# 4.5
Signed-off-by: Johan Hovold <johan@...nel.org>
---

Greg, Alan,

This patch for v4.6-rc7 fixes a 4.5-regression that broke system suspend
for a large class of devices, including USB-serial devices, for example
when USB persist is enabled.

We may be able to find a way around this, but since it's a user-visible
regression and late in the rc-cycle, I believe reverting the offending
commit is the right thing to do.

Thanks,
Johan

 drivers/usb/core/port.c | 6 ------
 drivers/usb/core/usb.c  | 8 +-------
 2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 14718a9ffcfb..460c855be0d0 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -249,18 +249,12 @@ static int usb_port_runtime_suspend(struct device *dev)

 	return retval;
 }
-
-static int usb_port_prepare(struct device *dev)
-{
-	return 1;
-}
 #endif

 static const struct dev_pm_ops usb_port_pm_ops = {
 #ifdef CONFIG_PM
 	.runtime_suspend =	usb_port_runtime_suspend,
 	.runtime_resume =	usb_port_runtime_resume,
-	.prepare =		usb_port_prepare,
 #endif
 };

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index dcb85e3cd5a7..479187c32571 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -312,13 +312,7 @@ static int usb_dev_uevent(struct device *dev, struct kobj_uevent_env *env)

 static int usb_dev_prepare(struct device *dev)
 {
-	struct usb_device *udev = to_usb_device(dev);
-
-	/* Return 0 if the current wakeup setting is wrong, otherwise 1 */
-	if (udev->do_remote_wakeup != device_may_wakeup(dev))
-		return 0;
-
-	return 1;
+	return 0;		/* Implement eventually? */
 }

 static void usb_dev_complete(struct device *dev)
-- 
2.7.3