[PATCH 3/4] xhci: Finetune host initiated USB3 rootport link suspend and resume

[Kai-Heng Feng]

From: Mathias Nyman <mathias.nyman at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/1868217

Depending on the current link state the steps to resume the link to U0
varies. The normal case when a port is suspended (U3) we set the link
to U0 and wait for a port event when U3exit completed and port moved to
U0.

If the port is in U1/U2, then no event is issued, just set link to U0

If port is in Resume or Recovery state then the device has already
initiated resume, and this host initiated resume is racing against it.
Port event handler for device initiated resume will set link to U0,
just wait for the port to reach U0 before returning.

Signed-off-by: Mathias Nyman <mathias.nyman at linux.intel.com>
Link: https://lore.kernel.org/r/20200312144517.1593-9-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit ceca49382ac20e06ce04c21279c7f2868c4ec1d4 linux-next)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/usb/host/xhci-hub.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 02f52d4f74df..a9c87eb8951e 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -1307,20 +1307,34 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
 				goto error;
 			}
 
+			/*
+			 * set link to U0, steps depend on current link state.
+			 * U3: set link to U0 and wait for u3exit completion.
+			 * U1/U2:  no PLC complete event, only set link to U0.
+			 * Resume/Recovery: device initiated U0, only wait for
+			 * completion
+			 */
 			if (link_state == USB_SS_PORT_LS_U0) {
-				if ((temp & PORT_PLS_MASK) == XDEV_U0)
-					break;
+				u32 pls = temp & PORT_PLS_MASK;
+				bool wait_u0 = false;
 
-				if (!((temp & PORT_PLS_MASK) == XDEV_U1 ||
-				    (temp & PORT_PLS_MASK) == XDEV_U2 ||
-				    (temp & PORT_PLS_MASK) == XDEV_U3)) {
-					xhci_warn(xhci, "Can only set port %d to U0 from U state\n",
-							wIndex);
-					goto error;
+				/* already in U0 */
+				if (pls == XDEV_U0)
+					break;
+				if (pls == XDEV_U3 ||
+				    pls == XDEV_RESUME ||
+				    pls == XDEV_RECOVERY) {
+					wait_u0 = true;
+					reinit_completion(&bus_state->u3exit_done[wIndex]);
+				}
+				if (pls <= XDEV_U3) /* U1, U2, U3 */
+					xhci_set_link_state(xhci, ports[wIndex],
+							    USB_SS_PORT_LS_U0);
+				if (!wait_u0) {
+					if (pls > XDEV_U3)
+						goto error;
+					break;
 				}
-				reinit_completion(&bus_state->u3exit_done[wIndex]);
-				xhci_set_link_state(xhci, ports[wIndex],
-						    USB_SS_PORT_LS_U0);
 				spin_unlock_irqrestore(&xhci->lock, flags);
 				if (!wait_for_completion_timeout(&bus_state->u3exit_done[wIndex],
 								 msecs_to_jiffies(100)))
-- 
2.17.1