The port reset code bails out early if the current connect status is cleared (device disconnected). If we're issuing a hot reset, it may also look at the link state before the reset is finished. Section 10.14.2.6 of the USB 3.0 spec says that when a port enters the Error state or Resetting state, the port connection bit retains the value from the previous state. Therefore we can't trust it until the reset finishes. Also, the xHCI spec section 4.19.1.2.5 says software shall ignore the link state while the port is resetting, as it can be in an unknown state. The port state during reset is also unknown for USB 2.0 hubs. The hub sends a reset signal by driving the bus into an SE0 state. This overwhelms the "connect" signal from the device, so the port can't tell whether anything is connected or not. Fix the port reset code to ignore the port link state and current connect bit until the reset finishes. This patch should be backported to all stable kernels. Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/usb/core/hub.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index b9ce5e8..b7b055f 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2534,6 +2534,10 @@ static int hub_port_wait_reset(struct usb_hub *hub, int port1, if (ret < 0) return ret; + /* The port state is unknown until the reset completes. */ + if ((portstatus & USB_PORT_STAT_RESET)) + goto delay; + /* * Some buggy devices require a warm reset to be issued even * when the port appears not to be connected. @@ -2601,6 +2605,7 @@ static int hub_port_wait_reset(struct usb_hub *hub, int port1, return 0; } +delay: /* switch to the long delay after two short delay failures */ if (delay_time >= 2 * HUB_SHORT_RESET_TIME) delay = HUB_LONG_RESET_TIME; -- 1.7.9 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
