This was seen on a Dell Precision 5520 using it's WD15 dock. The dock's Ethernet device interfaces with the laptop through one of it's USB3 ports. While idle, the Ethernet device and HCD are suspended by runtime PM, being the only device connected on the bus. Then, both are resumed on behalf of the Ethernet device, which has remote wake-up capabilities. The Ethernet device was observed to randomly disconnect from the USB port shortly after submitting it's remote wake-up request. Probably a weird timing issue yet to be investigated. This causes runtime PM to busyloop causing some tangible CPU load. The reason is the port gets stuck in the middle of a remote wake-up operation, waiting for the device to switch to U0. This never happens, leaving "port_remote_wakeup" enabled, and automatically triggering a failure on any further suspend operation. This patch clears "port_remote_wakeup" upon detecting a device with a wrong resuming port state (see Table 4-9 in 4.15.2.3). Making sure the above mentioned situation doesn't trigger a PM busyloop. Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> --- drivers/usb/host/xhci-hub.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index 3abe70ff1b1e..53f5ee50ef8c 100644 --- a/drivers/usb/host/xhci-hub.c +++ b/drivers/usb/host/xhci-hub.c @@ -1047,8 +1047,8 @@ static u32 xhci_get_port_status(struct usb_hcd *hcd, xhci_get_usb2_port_status(port, &status, raw_port_status, flags); /* - * Clear stale usb2 resume signalling variables in case port changed - * state during resume signalling. For example on error + * Clear stale resume signalling variables in case port changed + * state during resume signalling. For example on error. */ if ((bus_state->resume_done[wIndex] || test_bit(wIndex, &bus_state->resuming_ports)) && @@ -1057,6 +1057,12 @@ static u32 xhci_get_port_status(struct usb_hcd *hcd, bus_state->resume_done[wIndex] = 0; clear_bit(wIndex, &bus_state->resuming_ports); usb_hcd_end_port_resume(&hcd->self, wIndex); + } else if (bus_state->port_remote_wakeup & (1 << port->hcd_portnum) && + ((raw_port_status & PORT_PLS_MASK) != XDEV_RESUME || + !(raw_port_status & PORT_CONNECT) || + !(raw_port_status & PORT_PE) || + raw_port_status & PORT_OC)) { + bus_state->port_remote_wakeup &= ~(1 << port->hcd_portnum); } if (bus_state->port_c_suspend & (1 << wIndex)) -- 2.21.0