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>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b90c628..88f1db2 100644 (file)
--- 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 326308e..c77d877 100644 (file)
--- 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 fe1b6d0..cd3f9dc 100644 (file)
--- 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)) {