linux-kernel - [PATCH v2 1/1] usb: Check if port status is equal to RxDetect

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Message-Id: <1405604056-18987-2-git-send-email-gavin.guo@canonical.com>
Date:	Thu, 17 Jul 2014 21:34:16 +0800
From:	Gavin Guo <gavin.guo@...onical.com>
To:	stern@...land.harvard.edu, sarah.a.sharp@...ux.intel.com,
	mathias.nyman@...el.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	yk@...onical.com, anthony.wong@...onical.com,
	gerald.yang@...onical.com
Subject: [PATCH v2 1/1] usb: Check if port status is equal to RxDetect

When using USB 3.0 pen drive with the [AMD] FCH USB XHCI Controller
[1022:7814], the second hotplugging will experience the USB 3.0 pen
drive is recognized as high-speed device. After bisecting the kernel,
I found the commit number 41e7e056cdc662f704fa9262e5c6e213b4ab45dd
(USB: Allow USB 3.0 ports to be disabled.) causes the bug. After doing
some experiments, the bug can be fixed by avoiding executing the function
hub_usb3_port_disable(). Because the port status with [AMD] FCH USB
XHCI Controlleris [1022:7814] is already in RxDetect
(I tried printing out the port status before setting to Disabled state),
it's reasonable to check the port status before really executing
hub_usb3_port_disable().

Fixes: 41e7e056cdc6 (USB: Allow USB 3.0 ports to be disabled.)
Signed-off-by: Gavin Guo <gavin.guo@...onical.com>
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Cc: <stable@...r.kernel.org>
---
 drivers/usb/core/hub.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 21b99b4..0e950ad 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -889,6 +889,25 @@ static int hub_usb3_port_disable(struct usb_hub *hub, int port1)
 	if (!hub_is_superspeed(hub->hdev))
 		return -EINVAL;
 
+	ret = hub_port_status(hub, port1, &portstatus, &portchange);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * USB controller Advanced Micro Devices, Inc. [AMD] FCH USB XHCI
+	 * Controller [1022:7814] will have spurious result making the following
+	 * usb 3.0 device hotplugging route to the 2.0 root hub and recognized
+	 * as high-speed device if we set the usb 3.0 port link state to
+	 * Disabled. Since it's already in USB_SS_PORT_LS_RX_DETECT state, we
+	 * check the state here to avoid the bug.
+	 */
+	if ((portstatus & USB_PORT_STAT_LINK_STATE) ==
+				USB_SS_PORT_LS_RX_DETECT) {
+		dev_dbg(&hub->ports[port1 - 1]->dev,
+			 "Not disabling port; link state is RxDetect\n");
+		return ret;
+	}
+
 	ret = hub_set_port_link_state(hub, port1, USB_SS_PORT_LS_SS_DISABLED);
 	if (ret)
 		return ret;
-- 
2.0.0

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