From c52804a472649b2e5005342308739434cbd51119 Mon Sep 17 00:00:00 2001 From: Sarah Sharp Date: Tue, 27 Nov 2012 12:30:23 -0800 Subject: [PATCH] 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 Acked-by: Alan Stern Cc: stable@vger.kernel.org --- drivers/usb/host/xhci-hub.c | 7 +++++++ drivers/usb/host/xhci-ring.c | 9 +++++++++ drivers/usb/host/xhci.c | 10 ++++++++++ 3 files changed, 26 insertions(+) diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index a7dd4f311e14..68914429482f 100644 --- 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 cbb44b7b9d65..59fb5c677dbe 100644 --- 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 5c72c431bab1..f1f01a834ba7 100644 --- 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 */ -- 2.20.1