[PATCH] usb: Handle USB3 remote wakeup for LPM enabled devices correctly

[PATCH] usb: Handle USB3 remote wakeup for LPM enabled devices correctly

[Mathias Nyman]

From: "Lee, Chiasheng" <chiasheng.lee@intel.com>

With Link Power Management (LPM) enabled USB3 links transition to low
power U1/U2 link states from U0 state automatically.

Current hub code detects USB3 remote wakeups by checking if the software
state still shows suspended, but the link has transitioned from suspended
U3 to enabled U0 state.

As it takes some time before the hub thread reads the port link state
after a USB3 wake notification, the link may have transitioned from U0
to U1/U2, and wake is not detected by hub code.

Fix this by handling U1/U2 states in the same way as U0 in USB3 wakeup
handling

This patch should be added to stable kernels since 4.13 where LPM was
kept enabled during suspend/resume

Cc: <stable@vger.kernel.org> # v4.13+
Signed-off-by: Lee, Chiasheng <chiasheng.lee@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/core/hub.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 2f94568..2c8e60c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3617,6 +3617,7 @@ static int hub_handle_remote_wakeup(struct usb_hub *hub, unsigned int port,
 	struct usb_device *hdev;
 	struct usb_device *udev;
 	int connect_change = 0;
+	u16 link_state;
 	int ret;
 
 	hdev = hub->hdev;
@@ -3626,9 +3627,11 @@ static int hub_handle_remote_wakeup(struct usb_hub *hub, unsigned int port,
 			return 0;
 		usb_clear_port_feature(hdev, port, USB_PORT_FEAT_C_SUSPEND);
 	} else {
+		link_state = portstatus & USB_PORT_STAT_LINK_STATE;
 		if (!udev || udev->state != USB_STATE_SUSPENDED ||
-				 (portstatus & USB_PORT_STAT_LINK_STATE) !=
-				 USB_SS_PORT_LS_U0)
+				(link_state != USB_SS_PORT_LS_U0 &&
+				 link_state != USB_SS_PORT_LS_U1 &&
+				 link_state != USB_SS_PORT_LS_U2))
 			return 0;
 	}
 
-- 
2.7.4