[PATCH v3 1/1] usb: hub: Fix auto-remount of safely removed or ejected USB-3 devices

[Mathias Nyman <mathias.nyman@linux.intel.com>]

USB-3 does not have any link state that will avoid negotiating a connection
with a plugged-in cable but will signal the host when the cable is
unplugged.

For USB-3 we used to first set the link to Disabled, then to RxDdetect to
be able to detect cable connects or disconnects. But in RxDetect the
connected device is detected again and eventually enabled.

Instead set the link into U3 and disable remote wakeups for the device.
This is what Windows does, and what Alan Stern suggested.

Cc: stable@vger.kernel.org
Cc: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>

---
Changes since v2:
- clear udev->do_remote_wakeup as suggested
- add Acked-by: Alan Stern as agreed

Changes since RFC-PATCH:
- send port_dev as an argument
- move checking and disabling remote wakeup to a function under CONFIG_PM
- set device state to USB_STATE_NOTATTACHED _after_ disabling remote wakup
  and port disable.
---
 drivers/usb/core/hub.c | 101 ++++++++++++++++++-------------------------------
 1 file changed, 36 insertions(+), 65 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 76e80d8..71bf1c7 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -103,6 +103,8 @@
 
 static void hub_release(struct kref *kref);
 static int usb_reset_and_verify_device(struct usb_device *udev);
+static void hub_usb3_port_prepare_disable(struct usb_hub *hub,
+					  struct usb_port *port_dev);
 
 static inline char *portspeed(struct usb_hub *hub, int portstatus)
 {
@@ -901,82 +903,28 @@ static int hub_set_port_link_state(struct usb_hub *hub, int port1,
 }
 
 /*
- * If USB 3.0 ports are placed into the Disabled state, they will no longer
- * detect any device connects or disconnects.  This is generally not what the
- * USB core wants, since it expects a disabled port to produce a port status
- * change event when a new device connects.
- *
- * Instead, set the link state to Disabled, wait for the link to settle into
- * that state, clear any change bits, and then put the port into the RxDetect
- * state.
+ * USB-3 does not have a similar link state as USB-2 that will avoid negotiating
+ * a connection with a plugged-in cable but will signal the host when the cable
+ * is unplugged. Disable remote wake and set link state to U3 for USB-3 devices
  */
-static int hub_usb3_port_disable(struct usb_hub *hub, int port1)
-{
-	int ret;
-	int total_time;
-	u16 portchange, portstatus;
-
-	if (!hub_is_superspeed(hub->hdev))
-		return -EINVAL;
-
-	ret = hub_port_status(hub, port1, &portstatus, &portchange);
-	if (ret < 0)
-		return ret;
-
-	/*
-	 * USB controller Advanced Micro Devices, Inc. [AMD] FCH USB XHCI
-	 * Controller [1022:7814] will have spurious result making the following
-	 * usb 3.0 device hotplugging route to the 2.0 root hub and recognized
-	 * as high-speed device if we set the usb 3.0 port link state to
-	 * Disabled. Since it's already in USB_SS_PORT_LS_RX_DETECT state, we
-	 * check the state here to avoid the bug.
-	 */
-	if ((portstatus & USB_PORT_STAT_LINK_STATE) ==
-				USB_SS_PORT_LS_RX_DETECT) {
-		dev_dbg(&hub->ports[port1 - 1]->dev,
-			 "Not disabling port; link state is RxDetect\n");
-		return ret;
-	}
-
-	ret = hub_set_port_link_state(hub, port1, USB_SS_PORT_LS_SS_DISABLED);
-	if (ret)
-		return ret;
-
-	/* Wait for the link to enter the disabled state. */
-	for (total_time = 0; ; total_time += HUB_DEBOUNCE_STEP) {
-		ret = hub_port_status(hub, port1, &portstatus, &portchange);
-		if (ret < 0)
-			return ret;
-
-		if ((portstatus & USB_PORT_STAT_LINK_STATE) ==
-				USB_SS_PORT_LS_SS_DISABLED)
-			break;
-		if (total_time >= HUB_DEBOUNCE_TIMEOUT)
-			break;
-		msleep(HUB_DEBOUNCE_STEP);
-	}
-	if (total_time >= HUB_DEBOUNCE_TIMEOUT)
-		dev_warn(&hub->ports[port1 - 1]->dev,
-				"Could not disable after %d ms\n", total_time);
-
-	return hub_set_port_link_state(hub, port1, USB_SS_PORT_LS_RX_DETECT);
-}
-
 static int hub_port_disable(struct usb_hub *hub, int port1, int set_state)
 {
 	struct usb_port *port_dev = hub->ports[port1 - 1];
 	struct usb_device *hdev = hub->hdev;
 	int ret = 0;
 
-	if (port_dev->child && set_state)
-		usb_set_device_state(port_dev->child, USB_STATE_NOTATTACHED);
 	if (!hub->error) {
-		if (hub_is_superspeed(hub->hdev))
-			ret = hub_usb3_port_disable(hub, port1);
-		else
+		if (hub_is_superspeed(hub->hdev)) {
+			hub_usb3_port_prepare_disable(hub, port_dev);
+			ret = hub_set_port_link_state(hub, port_dev->portnum,
+						      USB_SS_PORT_LS_U3);
+		} else {
 			ret = usb_clear_port_feature(hdev, port1,
 					USB_PORT_FEAT_ENABLE);
+		}
 	}
+	if (port_dev->child && set_state)
+		usb_set_device_state(port_dev->child, USB_STATE_NOTATTACHED);
 	if (ret && ret != -ENODEV)
 		dev_err(&port_dev->dev, "cannot disable (err = %d)\n", ret);
 	return ret;
@@ -4142,6 +4090,26 @@ void usb_unlocked_enable_lpm(struct usb_device *udev)
 }
 EXPORT_SYMBOL_GPL(usb_unlocked_enable_lpm);
 
+/* usb3 devices use U3 for disabled, make sure remote wakeup is disabled */
+static void hub_usb3_port_prepare_disable(struct usb_hub *hub,
+					  struct usb_port *port_dev)
+{
+	struct usb_device *udev = port_dev->child;
+	int ret;
+
+	if (udev && udev->port_is_suspended && udev->do_remote_wakeup) {
+		ret = hub_set_port_link_state(hub, port_dev->portnum,
+					      USB_SS_PORT_LS_U0);
+		if (!ret) {
+			msleep(USB_RESUME_TIMEOUT);
+			ret = usb_disable_remote_wakeup(udev);
+		}
+		if (ret)
+			dev_warn(&udev->dev,
+				 "Port disable: can't disable remote wake\n");
+		udev->do_remote_wakeup = 0;
+	}
+}
 
 #else	/* CONFIG_PM */
 
@@ -4149,6 +4117,9 @@ void usb_unlocked_enable_lpm(struct usb_device *udev)
 #define hub_resume		NULL
 #define hub_reset_resume	NULL
 
+static inline void hub_usb3_port_prepare_disable(struct usb_hub *hub,
+						 struct usb_port *port_dev) { }
+
 int usb_disable_lpm(struct usb_device *udev)
 {
 	return 0;
-- 
1.9.1