[RFC usb-next v3 2/2] usb: core: use phy_exit during suspend if wake up is not supported

[Martin Blumenstingl]

If the USB controller can wake up the system (which is the case for
example with the Mediatek USB3 IP) then we must not call phy_exit during
suspend to ensure that the USB controller doesn't have to re-enumerate
the devices during resume.
However, if the USB controller cannot wake up the system (which is the
case for example on various TI platforms using a dwc3 controller) then
we must call phy_exit during suspend. Otherwise the PHY driver keeps the
clocks enabled, which prevents the system from reaching the lowest power
levels in the suspend state.

Solve this by introducing two new functions in the PHY wrapper which are
dedicated to the suspend and resume handling.
If the controller can wake up the system the new usb_phy_roothub_suspend
function will simply call usb_phy_roothub_power_off. However, if wake up
is not supported by the controller it will also call
usb_phy_roothub_exit.
The also new usb_phy_roothub_resume function takes care of calling
usb_phy_roothub_init (if the controller can't wake up the system) in
addition to usb_phy_roothub_power_on.

Fixes: 07dbff0ddbd86c ("usb: core: add a wrapper for the USB PHYs on the HCD")
Fixes: 178a0bce05cbc1 ("usb: core: hcd: integrate the PHY wrapper into the HCD core")
Reported-by: Roger Quadros <rogerq at ti.com>
Suggested-by: Roger Quadros <rogerq at ti.com>
Suggested-by: Chunfeng Yun <chunfeng.yun at mediatek.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
---
 drivers/usb/core/hcd.c |  8 +++++---
 drivers/usb/core/phy.c | 35 +++++++++++++++++++++++++++++++++++
 drivers/usb/core/phy.h |  5 +++++
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 15b0418e3b6a..78bae4ecd68b 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2262,7 +2262,8 @@ int hcd_bus_suspend(struct usb_device *rhdev, pm_message_t msg)
 		hcd->state = HC_STATE_SUSPENDED;
 
 		if (!PMSG_IS_AUTO(msg))
-			usb_phy_roothub_power_off(hcd->phy_roothub);
+			usb_phy_roothub_suspend(hcd->self.sysdev,
+						hcd->phy_roothub);
 
 		/* Did we race with a root-hub wakeup event? */
 		if (rhdev->do_remote_wakeup) {
@@ -2302,7 +2303,8 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
 	}
 
 	if (!PMSG_IS_AUTO(msg)) {
-		status = usb_phy_roothub_power_on(hcd->phy_roothub);
+		status = usb_phy_roothub_resume(hcd->self.sysdev,
+						hcd->phy_roothub);
 		if (status)
 			return status;
 	}
@@ -2344,7 +2346,7 @@ int hcd_bus_resume(struct usb_device *rhdev, pm_message_t msg)
 		}
 	} else {
 		hcd->state = old_state;
-		usb_phy_roothub_power_off(hcd->phy_roothub);
+		usb_phy_roothub_suspend(hcd->self.sysdev, hcd->phy_roothub);
 		dev_dbg(&rhdev->dev, "bus %s fail, err %d\n",
 				"resume", status);
 		if (status != -ESHUTDOWN)
diff --git a/drivers/usb/core/phy.c b/drivers/usb/core/phy.c
index 44f008cda7a8..a39d9bb26a4f 100644
--- a/drivers/usb/core/phy.c
+++ b/drivers/usb/core/phy.c
@@ -157,3 +157,38 @@ void usb_phy_roothub_power_off(struct usb_phy_roothub *phy_roothub)
 		phy_power_off(roothub_entry->phy);
 }
 EXPORT_SYMBOL_GPL(usb_phy_roothub_power_off);
+
+int usb_phy_roothub_suspend(struct device *controller_dev,
+			    struct usb_phy_roothub *phy_roothub)
+{
+	usb_phy_roothub_power_off(phy_roothub);
+
+	/* keep the PHYs initialized so the device can wake up the system */
+	if (device_may_wakeup(controller_dev))
+		return 0;
+
+	return usb_phy_roothub_exit(phy_roothub);
+}
+EXPORT_SYMBOL_GPL(usb_phy_roothub_suspend);
+
+int usb_phy_roothub_resume(struct device *controller_dev,
+			   struct usb_phy_roothub *phy_roothub)
+{
+	int err;
+
+	/* if the device can't wake up the system _exit was called */
+	if (!device_may_wakeup(controller_dev)) {
+		err = usb_phy_roothub_init(phy_roothub);
+		if (err)
+			return err;
+	}
+
+	err = usb_phy_roothub_power_on(phy_roothub);
+
+	/* undo _init if _power_on failed */
+	if (err && !device_may_wakeup(controller_dev))
+		usb_phy_roothub_exit(phy_roothub);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(usb_phy_roothub_resume);
diff --git a/drivers/usb/core/phy.h b/drivers/usb/core/phy.h
index eb31253201ad..605555901d44 100644
--- a/drivers/usb/core/phy.h
+++ b/drivers/usb/core/phy.h
@@ -7,3 +7,8 @@ int usb_phy_roothub_exit(struct usb_phy_roothub *phy_roothub);
 
 int usb_phy_roothub_power_on(struct usb_phy_roothub *phy_roothub);
 void usb_phy_roothub_power_off(struct usb_phy_roothub *phy_roothub);
+
+int usb_phy_roothub_suspend(struct device *controller_dev,
+			    struct usb_phy_roothub *phy_roothub);
+int usb_phy_roothub_resume(struct device *controller_dev,
+			   struct usb_phy_roothub *phy_roothub);
-- 
2.16.3