From 3cd12f91514da6893954de479dc60b16d3b381f4 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 29 May 2014 12:58:46 -0700 Subject: [PATCH] usb: force warm reset to break link re-connect livelock Resuming a powered down port sometimes results in the port state being stuck in the training sequence. hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0 port1: can't get reconnection after setting port power on, status -110 hub 3-0:1.0: port 1 status 0000.02e0 after resume, -19 usb 3-1: can't resume, status -19 hub 3-0:1.0: logical disconnect on port 1 In the case above we wait for the port re-connect timeout of 2 seconds and observe that the port status is USB_SS_PORT_LS_POLLING (although it is likely toggling between this state and USB_SS_PORT_LS_RX_DETECT). This is indicative of a case where the device is failing to progress the link training state machine. It is resolved by issuing a warm reset to get the hub and device link state machines back in sync. hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0 usb usb3: port1 usb_port_runtime_resume requires warm reset hub 3-0:1.0: port 1 not warm reset yet, waiting 50ms usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd After a reconnect timeout when we expect the device to be present, force a warm reset of the device. Note that we can not simply look at the link status to determine if a warm reset is required as any of the training states USB_SS_PORT_LS_POLLING, USB_SS_PORT_LS_RX_DETECT, or USB_SS_PORT_LS_COMP_MOD are valid states that do not indicate the need for warm reset by themselves. Cc: Alan Stern Cc: Kukjin Kim Cc: Vincent Palatin Cc: Lan Tianyu Cc: Ksenia Ragiadakou Cc: Vivek Gautam Cc: Douglas Anderson Cc: Felipe Balbi Cc: Sunil Joshi Cc: Hans de Goede Acked-by: Julius Werner Signed-off-by: Dan Williams Acked-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- Reading git-format-patch failed