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

commit c52804a472649b2e5005342308739434cbd51119 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 0efc857ed1ebd4df13e25e52f4ca17482160fc56..8331893c75e32a571371d1f8e8b0997a075d73bc 100644 (file)
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -940,6 +940,7 @@ 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)];
@@ -971,6 +972,12 @@ 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 bf8bcc4dd788a2cba7e5a0a5179c7b77a8a40d62..01361f929f1dc321db3f0581b5d95d5d407a0160 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 b4063fc72b42c652d3d1dc413218004dc8379f68..b04134aa3462cfeaf79c2f61d79d74579bf39d2b 100644 (file)
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -880,6 +880,11 @@ int xhci_suspend(struct xhci_hcd *xhci)
        struct usb_hcd          *hcd = xhci_to_hcd(xhci);
        u32                     command;
 
+       /* 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);
@@ -1064,6 +1069,11 @@ 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 */