[PATCH 4/5] xhci: Return if xHCI doesn't support LPM

[Mathias Nyman <mathias.nyman@linux.intel.com>]

From: Kai-Heng Feng <kai.heng.feng@canonical.com>

Just return if xHCI is quirked to disable LPM. We can save some time
from reading registers and doing spinlocks.

Add stable tag as we want this patch together with the next one,
"Poll for U0 after disabling USB2 LPM" which fixes a suspend issue
for some USB2 LPM devices

Cc: stable@vger.kernel.org
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 03b64b73eb99..f97106e2860f 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4391,6 +4391,9 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 	int		hird, exit_latency;
 	int		ret;
 
+	if (xhci->quirks & XHCI_HW_LPM_DISABLE)
+		return -EPERM;
+
 	if (hcd->speed >= HCD_USB3 || !xhci->hw_lpm_support ||
 			!udev->lpm_capable)
 		return -EPERM;
@@ -4413,7 +4416,7 @@ static int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 	xhci_dbg(xhci, "%s port %d USB2 hardware LPM\n",
 			enable ? "enable" : "disable", port_num + 1);
 
-	if (enable && !(xhci->quirks & XHCI_HW_LPM_DISABLE)) {
+	if (enable) {
 		/* Host supports BESL timeout instead of HIRD */
 		if (udev->usb2_hw_lpm_besl_capable) {
 			/* if device doesn't have a preferred BESL value use a
-- 
2.17.1