From 940c098da89d74b015ec5b2ddf34408a6d7d624d Mon Sep 17 00:00:00 2001 From: Keiya Nobuta Date: Thu, 9 Jan 2020 14:14:48 +0900 Subject: [PATCH] usb: core: hub: Improved device recognition on remote wakeup commit 9c06ac4c83df6d6fbdbf7488fbad822b4002ba19 upstream. If hub_activate() is called before D+ has stabilized after remote wakeup, the following situation might occur: __ ___________________ / \ / D+ __/ \__/ Hub _______________________________ | ^ ^ ^ | | | | Host _____v__|___|___________|______ | | | | | | | \-- Interrupt Transfer (*3) | | \-- ClearPortFeature (*2) | \-- GetPortStatus (*1) \-- Host detects remote wakeup - D+ goes high, Host starts running by remote wakeup - D+ is not stable, goes low - Host requests GetPortStatus at (*1) and gets the following hub status: - Current Connect Status bit is 0 - Connect Status Change bit is 1 - D+ stabilizes, goes high - Host requests ClearPortFeature and thus Connect Status Change bit is cleared at (*2) - After waiting 100 ms, Host starts the Interrupt Transfer at (*3) - Since the Connect Status Change bit is 0, Hub returns NAK. In this case, port_event() is not called in hub_event() and Host cannot recognize device. To solve this issue, flag change_bits even if only Connect Status Change bit is 1 when got in the first GetPortStatus. This issue occurs rarely because it only if D+ changes during a very short time between GetPortStatus and ClearPortFeature. However, it is fatal if it occurs in embedded system. Signed-off-by: Keiya Nobuta Cc: stable Acked-by: Alan Stern Link: https://lore.kernel.org/r/20200109051448.28150-1-nobuta.keiya@fujitsu.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/hub.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index acf4752302a6..9f05f9a81f69 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1162,6 +1162,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) * PORT_OVER_CURRENT is not. So check for any of them. */ if (udev || (portstatus & USB_PORT_STAT_CONNECTION) || + (portchange & USB_PORT_STAT_C_CONNECTION) || (portstatus & USB_PORT_STAT_OVERCURRENT) || (portchange & USB_PORT_STAT_C_OVERCURRENT)) set_bit(port1, hub->change_bits); -- 2.20.1