usb: force warm reset to break link re-connect livelock

Resuming a powered down port sometimes results in the port state being
stuck in the training sequence.

 hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0
 port1: can't get reconnection after setting port  power on, status -110
 hub 3-0:1.0: port 1 status 0000.02e0 after resume, -19
 usb 3-1: can't resume, status -19
 hub 3-0:1.0: logical disconnect on port 1

In the case above we wait for the port re-connect timeout of 2 seconds
and observe that the port status is USB_SS_PORT_LS_POLLING (although it
is likely toggling between this state and USB_SS_PORT_LS_RX_DETECT).
This is indicative of a case where the device is failing to progress the
link training state machine.

It is resolved by issuing a warm reset to get the hub and device link
state machines back in sync.

 hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0
 usb usb3: port1 usb_port_runtime_resume requires warm reset
 hub 3-0:1.0: port 1 not warm reset yet, waiting 50ms
 usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd

After a reconnect timeout when we expect the device to be present, force
a warm reset of the device.  Note that we can not simply look at the
link status to determine if a warm reset is required as any of the
training states USB_SS_PORT_LS_POLLING, USB_SS_PORT_LS_RX_DETECT, or
USB_SS_PORT_LS_COMP_MOD are valid states that do not indicate the need
for warm reset by themselves.

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Vincent Palatin <vpalatin@chromium.org>
Cc: Lan Tianyu <tianyu.lan@intel.com>
Cc: Ksenia Ragiadakou <burzalodowa@gmail.com>
Cc: Vivek Gautam <gautam.vivek@samsung.com>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Sunil Joshi <joshi@samsung.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Acked-by: Julius Werner <jwerner@chromium.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 39 insertions, 20 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b90c6287bf47..88f1db27e0af 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2587,13 +2587,20 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
 /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
  * Port worm reset is required to recover
  */
-static bool hub_port_warm_reset_required(struct usb_hub *hub, u16 portstatus)
+static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
+                u16 portstatus)
 {
-        return hub_is_superspeed(hub->hdev) &&
-                (((portstatus & USB_PORT_STAT_LINK_STATE) ==
-                  USB_SS_PORT_LS_SS_INACTIVE) ||
-                 ((portstatus & USB_PORT_STAT_LINK_STATE) ==
-                  USB_SS_PORT_LS_COMP_MOD)) ;
+        u16 link_state;
+
+        if (!hub_is_superspeed(hub->hdev))
+                return false;
+
+        if (test_bit(port1, hub->warm_reset_bits))
+                return true;
+
+        link_state = portstatus & USB_PORT_STAT_LINK_STATE;
+        return link_state == USB_SS_PORT_LS_SS_INACTIVE
+                || link_state == USB_SS_PORT_LS_COMP_MOD;
 }
 
 static int hub_port_wait_reset(struct usb_hub *hub, int port1,
@@ -2630,7 +2637,7 @@ static int hub_port_wait_reset(struct usb_hub *hub, int port1,
         if ((portstatus & USB_PORT_STAT_RESET))
                 return -EBUSY;
 
-        if (hub_port_warm_reset_required(hub, portstatus))
+        if (hub_port_warm_reset_required(hub, port1, portstatus))
                 return -ENOTCONN;
 
         /* Device went away? */
@@ -2730,9 +2737,10 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
                 if (status < 0)
                         goto done;
 
-                if (hub_port_warm_reset_required(hub, portstatus))
+                if (hub_port_warm_reset_required(hub, port1, portstatus))
                         warm = true;
         }
+        clear_bit(port1, hub->warm_reset_bits);
 
         /* Reset the port */
         for (i = 0; i < PORT_RESET_TRIES; i++) {
@@ -2769,7 +2777,8 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
                                         &portstatus, &portchange) < 0)
                                 goto done;
 
-                        if (!hub_port_warm_reset_required(hub, portstatus))
+                        if (!hub_port_warm_reset_required(hub, port1,
+                                        portstatus))
                                 goto done;
 
                         /*
@@ -2856,8 +2865,13 @@ static int check_port_resume_type(struct usb_device *udev,
 {
         struct usb_port *port_dev = hub->ports[port1 - 1];
 
+        /* Is a warm reset needed to recover the connection? */
+        if (status == 0 && udev->reset_resume
+                && hub_port_warm_reset_required(hub, port1, portstatus)) {
+                /* pass */;
+        }
         /* Is the device still present? */
-        if (status || port_is_suspended(hub, portstatus) ||
+        else if (status || port_is_suspended(hub, portstatus) ||
                         !port_is_power_on(hub, portstatus) ||
                         !(portstatus & USB_PORT_STAT_CONNECTION)) {
                 if (status >= 0)
@@ -4872,7 +4886,7 @@ static void port_event(struct usb_hub *hub, int port1)
          * Warm reset a USB3 protocol port if it's in
          * SS.Inactive state.
          */
-        if (hub_port_warm_reset_required(hub, portstatus)) {
+        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)
                                 || udev->state == USB_STATE_NOTATTACHED) {
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 326308e53961..c77d8778af4b 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -52,6 +52,8 @@ struct usb_hub {
         unsigned long           power_bits[1]; /* ports that are powered */
         unsigned long           child_usage_bits[1]; /* ports powered on for
                                                         children */
+        unsigned long           warm_reset_bits[1]; /* ports requesting warm
+                                                        reset recovery */
 #if USB_MAXCHILDREN > 31 /* 8*sizeof(unsigned long) - 1 */
 #error event_bits[] is too short!
 #endif
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index fe1b6d0967e3..cd3f9dc24a06 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -103,16 +103,19 @@ static int usb_port_runtime_resume(struct device *dev)
         msleep(hub_power_on_good_delay(hub));
         if (udev && !retval) {
                 /*
-                 * Attempt to wait for usb hub port to be reconnected in order
-                 * to make the resume procedure successful.  The device may have
-                 * disconnected while the port was powered off, so ignore the
-                 * return status.
+                 * Our preference is to simply wait for the port to reconnect,
+                 * as that is the lowest latency method to restart the port.
+                 * However, there are cases where toggling port power results in
+                 * the host port and the device port getting out of sync causing
+                 * a link training live lock.  Upon timeout, flag the port as
+                 * needing warm reset recovery (to be performed later by
+                 * usb_port_resume() as requested via usb_wakeup_notification())
                  */
-                retval = hub_port_debounce_be_connected(hub, port1);
-                if (retval < 0)
-                        dev_dbg(&port_dev->dev, "can't get reconnection after setting port  power on, status %d\n",
-                                        retval);
-                retval = 0;
+                if (hub_port_debounce_be_connected(hub, port1) < 0) {
+                        dev_dbg(&port_dev->dev, "reconnect timeout\n");
+                        if (hub_is_superspeed(hdev))
+                                set_bit(port1, hub->warm_reset_bits);
+                }
 
                 /* Force the child awake to revalidate after the power loss. */
                 if (!test_and_set_bit(port1, hub->child_usage_bits)) {