linux-kernel - [PATCH] usb: core: Fix side effect of clear port feature in hub port reset

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Date:	Tue,  1 Sep 2015 16:31:21 +0900
From:	"hyunho747.kim" <hyunho747.kim@....com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-kernel@...r.kernel.org,
	"hyunho747.kim" <hyunho747.kim@....com>
Subject: [PATCH] usb: core: Fix side effect of clear port feature in hub port reset

After successful port reset by set_port_feature, some devices show
immediate link connection which generates port connect change interrupt.
But, the next step is an unconditional usb_clear_port_feature
and this flow always clears USB_PORT_FEAT_C_CONNECTION bit in port status
though next kick_khubd is reserved by link connection interrupt.
This flow can make an ambiguous state in the next port_evnet operation,
port_status is connected state such as 0x203 but
port_change is zero value caused by the previous clear port feature.
So, port_event can't call hub_port_connect_change and
there is no other way to peform connect procedure.

Signed-off-by: hyunho747.kim <hyunho747.kim@....com>
---
 drivers/usb/core/hub.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 73dfa19..4508aff 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2761,18 +2761,21 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
 
 		/* Check for disconnect or reset */
 		if (status == 0 || status == -ENOTCONN || status == -ENODEV) {
-			usb_clear_port_feature(hub->hdev, port1,
+			if (status)
+				usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_RESET);
 
 			if (!hub_is_superspeed(hub->hdev))
 				goto done;
 
-			usb_clear_port_feature(hub->hdev, port1,
+			if (status) {
+				usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_BH_PORT_RESET);
-			usb_clear_port_feature(hub->hdev, port1,
+				usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_PORT_LINK_STATE);
-			usb_clear_port_feature(hub->hdev, port1,
+				usb_clear_port_feature(hub->hdev, port1,
 					USB_PORT_FEAT_C_CONNECTION);
+			}
 
 			/*
 			 * If a USB 3.0 device migrates from reset to an error
-- 
2.2.1

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