xhci: Avoid "dead ports", add roothub port polling. (c52804a4) · Commits · 戴 / test

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 "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

drivers/usb/host/xhci-hub.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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;

drivers/usb/host/xhci-ring.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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);

drivers/usb/host/xhci.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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 */

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