usb: Handle USB3 remote wakeup for LPM enabled devices correctly [Linux 4.9.187]

This Linux kernel change "usb: Handle USB3 remote wakeup for LPM enabled devices correctly" is included in the Linux 4.9.187 release. This change is authored by Lee, Chiasheng <chiasheng.lee [at] intel.com> on Thu Jun 20 10:56:04 2019 +0300. The commit for this change in Linux stable tree is 769ebef (patch) which is from upstream commit e244c46. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream e244c46.

usb: Handle USB3 remote wakeup for LPM enabled devices correctly

commit e244c4699f859cf7149b0781b1894c7996a8a1df upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

There are 7 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 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 3941df0..9f132fa 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3535,6 +3535,7 @@ 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;
@@ -3544,9 +3545,11 @@ 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;
    }

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