xhci: Avoid "dead ports", add roothub port polling.

The USB core hub thread (khubd) is designed with external USB hubs in
mind.  It expects that if a port status change bit is set, the hub will
continue to send a notification through the hub status data transfer.
Basically, it expects hub notifications to be level-triggered.

The xHCI host controller is designed to be edge-triggered on the logical
'OR' of all the port status change bits.  When all port status change
bits are clear, and a new change bit is set, the xHC will generate a
Port Status Change Event.  If another change bit is set in the same port
status register before the first bit is cleared, it will not send
another event.

This means that the hub code may lose port status changes because of
race conditions between clearing change bits.  The user sees this as a
"dead port" that doesn't react to device connects.

The fix is to turn on port polling whenever a new change bit is set.
Once the USB core issues a hub status request that shows that no change
bits are set in any USB ports, turn off port polling.

We can't allow the USB core to poll the roothub for port events during
host suspend because if the PCI host is in D3cold, the port registers
will be all f's.  Instead, stop the port polling timer, and
unconditionally restart it when the host resumes.  If there are no port
change bits set after the resume, the first call to hub_status_data will
disable polling.

This patch should be backported to stable kernels with the first xHCI
support, 2.6.31 and newer, that include the commit
0f2a79300a1471cf92ab43af165ea13555c8b0a5 "USB: xhci: Root hub support."
There will be merge conflicts because the check for HC_STATE_SUSPENDED
was moved into xhci_suspend in 3.8.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable@vger.kernel.org

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index a7dd4f311e14602607656d2b6a3ca6a6ce36ae7a..68914429482f30ff4afed47180aae563d07c5784 100644 (file)
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -984,6 +984,7 @@ int xhci_hub_status_data(struct usb_hcd *hcd, char *buf)
        int max_ports;
        __le32 __iomem **port_array;
        struct xhci_bus_state *bus_state;
+       bool reset_change = false;
 
        max_ports = xhci_get_ports(hcd, &port_array);
        bus_state = &xhci->bus_state[hcd_index(hcd)];
@@ -1015,6 +1016,12 @@ int xhci_hub_status_data(struct usb_hcd *hcd, char *buf)
                        buf[(i + 1) / 8] |= 1 << (i + 1) % 8;
                        status = 1;
                }
+               if ((temp & PORT_RC))
+                       reset_change = true;
+       }
+       if (!status && !reset_change) {
+               xhci_dbg(xhci, "%s: stopping port polling.\n", __func__);
+               clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
        }
        spin_unlock_irqrestore(&xhci->lock, flags);
        return status ? retval : 0;

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index cbb44b7b9d6553e01f9c2f45da23c8fad1b7fe92..59fb5c677dbe5cb899ef2f442a5a565bf0aa8dd6 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1725,6 +1725,15 @@ cleanup:
        if (bogus_port_status)
                return;
 
+       /*
+        * xHCI port-status-change events occur when the "or" of all the
+        * status-change bits in the portsc register changes from 0 to 1.
+        * New status changes won't cause an event if any other change
+        * bits are still set.  When an event occurs, switch over to
+        * polling to avoid losing status changes.
+        */
+       xhci_dbg(xhci, "%s: starting port polling.\n", __func__);
+       set_bit(HCD_FLAG_POLL_RH, &hcd->flags);
        spin_unlock(&xhci->lock);
        /* Pass this up to the core */
        usb_hcd_poll_rh_status(hcd);

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 5c72c431bab18da941ec9a1a235c134086065482..f1f01a834ba792cee0935c5ffb9373d53fb368bd 100644 (file)
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -884,6 +884,11 @@ int xhci_suspend(struct xhci_hcd *xhci)
                        xhci->shared_hcd->state != HC_STATE_SUSPENDED)
                return -EINVAL;
 
+       /* Don't poll the roothubs on bus suspend. */
+       xhci_dbg(xhci, "%s: stopping port polling.\n", __func__);
+       clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
+       del_timer_sync(&hcd->rh_timer);
+
        spin_lock_irq(&xhci->lock);
        clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
        clear_bit(HCD_FLAG_HW_ACCESSIBLE, &xhci->shared_hcd->flags);
@@ -1069,6 +1074,11 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
        if (xhci->quirks & XHCI_COMP_MODE_QUIRK)
                compliance_mode_recovery_timer_init(xhci);
 
+       /* Re-enable port polling. */
+       xhci_dbg(xhci, "%s: starting port polling.\n", __func__);
+       set_bit(HCD_FLAG_POLL_RH, &hcd->flags);
+       usb_hcd_poll_rh_status(hcd);
+
        return retval;
 }
 #endif /* CONFIG_PM */