[PATCH 4/5] usb: hub: reorder USB3 link power management enable requests

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

Several usb requests are needed to allow a USB3 link to enter U1/U2
hardware link power management LPM states. Reorder these requests
and send the more significant and likely to succeed first.
This is similar to the change done for disabling LPM

Enable LPM by first sending requests to the upstream hub of the device
SetPortFeature(U1_TIMEOUT)
SetPortFeature(U2_TIMEOUT)

These are more likely to succeed due to the shorter path, and LPM can
be considered enabled as link may go to U1/U2 LPM states after those.

Send the requests to the device after this, they allow the device
to initialte U1/U2 link transitions. Hub can already initiate U1/U2
SetFeature(U1_ENABLE)
SetFeature(U2_ENABLE)

Fail fast and bail out if a requests to the device fails.

This changes device initated LPM policy a bit. Device is no longer
able to initiate U2 if it failed or is not allowed to initiate
U1.

Enabling and disabling Link power management is done as part of
hub work. Avoid trying to send additional USB requests to a device
when there are known issues. It just causes hub work to block for
even longer.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/core/hub.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index ccf21bb49038..d534d7b4606c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4160,7 +4160,7 @@ static int usb_set_device_initiated_lpm(struct usb_device *udev,
 				"for unconfigured device.\n",
 				__func__, str_enable_disable(enable),
 				usb3_lpm_names[state]);
-		return 0;
+		return -EINVAL;
 	}
 
 	if (enable) {
@@ -4341,13 +4341,6 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
 		return;
 	}
 
-	/*
-	 * Enable device initiated U1/U2 with a SetFeature(U1/U2_ENABLE) request
-	 * if system exit latency is short enough and device is configured
-	 */
-	if (usb_device_may_initiate_lpm(udev, state))
-		usb_set_device_initiated_lpm(udev, state, true);
-
 	if (state == USB3_LPM_U1)
 		udev->usb3_lpm_u1_enabled = 1;
 	else if (state == USB3_LPM_U2)
@@ -4508,6 +4501,18 @@ void usb_enable_lpm(struct usb_device *udev)
 
 	if (port_dev->usb3_lpm_u2_permit)
 		usb_enable_link_state(hcd, udev, USB3_LPM_U2);
+
+	/*
+	 * Enable device initiated U1/U2 with a SetFeature(U1/U2_ENABLE) request
+	 * if system exit latency is short enough and device is configured
+	 */
+	if (usb_device_may_initiate_lpm(udev, USB3_LPM_U1)) {
+		if (usb_set_device_initiated_lpm(udev, USB3_LPM_U1, true))
+			return;
+
+		if (usb_device_may_initiate_lpm(udev, USB3_LPM_U2))
+			usb_set_device_initiated_lpm(udev, USB3_LPM_U2, true);
+	}
 }
 EXPORT_SYMBOL_GPL(usb_enable_lpm);
 
-- 
2.43.0