[PATCH] usb: hub: avoid warm port reset during USB3 disconnect

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

During disconnect USB-3 ports often go via SS.Inactive link error state
before the missing terminations are noticed, and link finally goes to
RxDetect state

Avoid immediately warm-resetting ports in SS.Inactive state.
Let ports settle for a while and re-read the link status a few times 20ms
apart to see if the ports transitions out of SS.Inactive.

According to USB 3.x spec 7.5.2, a port in SS.Inactive should
automatically check for missing far-end receiver termination every
12 ms (SSInactiveQuietTimeout)

The futile multiple warm reset retries of a disconnected device takes
a lot of time, also the resetting of a removed devices has caused cases
where the reset bit got stuck for a long time on xHCI roothub.
This lead to issues in detecting new devices connected to the same port
shortly after.

Tested-by: Mark Pearson <markpearson@lenovo.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/core/hub.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 00070a8a6507..e907dfa0ca6d 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2777,6 +2777,8 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
 #define PORT_INIT_TRIES		4
 #endif	/* CONFIG_USB_FEW_INIT_RETRIES */
 
+#define DETECT_DISCONNECT_TRIES 5
+
 #define HUB_ROOT_RESET_TIME	60	/* times are in msec */
 #define HUB_SHORT_RESET_TIME	10
 #define HUB_BH_RESET_TIME	50
@@ -5543,6 +5545,7 @@ static void port_event(struct usb_hub *hub, int port1)
 	struct usb_device *udev = port_dev->child;
 	struct usb_device *hdev = hub->hdev;
 	u16 portstatus, portchange;
+	int i = 0;
 
 	connect_change = test_bit(port1, hub->change_bits);
 	clear_bit(port1, hub->event_bits);
@@ -5619,17 +5622,27 @@ static void port_event(struct usb_hub *hub, int port1)
 		connect_change = 1;
 
 	/*
-	 * Warm reset a USB3 protocol port if it's in
-	 * SS.Inactive state.
+	 * Avoid trying to recover a USB3 SS.Inactive port with a warm reset if
+	 * the device was disconnected. A 12ms disconnect detect timer in
+	 * SS.Inactive state transitions the port to RxDetect automatically.
+	 * SS.Inactive link error state is common during device disconnect.
 	 */
-	if (hub_port_warm_reset_required(hub, port1, portstatus)) {
-		dev_dbg(&port_dev->dev, "do warm reset\n");
-		if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
+	while (hub_port_warm_reset_required(hub, port1, portstatus)) {
+		if ((i++ < DETECT_DISCONNECT_TRIES) && udev) {
+			u16 unused;
+
+			msleep(20);
+			hub_port_status(hub, port1, &portstatus, &unused);
+			dev_dbg(&port_dev->dev, "Wait for inactive link disconnect detect\n");
+			continue;
+		} else if (!udev || !(portstatus & USB_PORT_STAT_CONNECTION)
 				|| udev->state == USB_STATE_NOTATTACHED) {
+			dev_dbg(&port_dev->dev, "do warm reset, port only\n");
 			if (hub_port_reset(hub, port1, NULL,
 					HUB_BH_RESET_TIME, true) < 0)
 				hub_port_disable(hub, port1, 1);
 		} else {
+			dev_dbg(&port_dev->dev, "do warm reset, full device\n");
 			usb_unlock_port(port_dev);
 			usb_lock_device(udev);
 			usb_reset_device(udev);
@@ -5637,6 +5650,7 @@ static void port_event(struct usb_hub *hub, int port1)
 			usb_lock_port(port_dev);
 			connect_change = 0;
 		}
+		break;
 	}
 
 	if (connect_change)
-- 
2.25.1