usb: xhci: omit duplicate actions when suspending a runtime suspended host.

If the xhci-plat.c is the platform driver, after the runtime pm is
enabled, the xhci_suspend is called if nothing is connected on
the port. When the system goes to suspend, it will call xhci_suspend again
if USB wakeup is enabled.

Since the runtime suspend wakeup setting is not always the same as
system suspend wakeup setting, eg, at runtime suspend we always need
wakeup if the controller is in low power mode; but at system suspend,
we may not need wakeup. So, we move the judgement after changing
wakeup setting.

[commit message rewording -Mathias]
Reviewed-by: NJun Li <jun.li@nxp.com>
Signed-off-by: NPeter Chen <peter.chen@nxp.com>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200918131752.16488-8-mathias.nyman@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.c

@@ -982,12 +982,15 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
 			xhci->shared_hcd->state != HC_STATE_SUSPENDED)
 		return -EINVAL;
 
-	xhci_dbc_suspend(xhci);
-
 	/* Clear root port wake on bits if wakeup not allowed. */
 	if (!do_wakeup)
 		xhci_disable_port_wake_on_bits(xhci);
 
+	if (!HCD_HW_ACCESSIBLE(hcd))
+		return 0;
+
+	xhci_dbc_suspend(xhci);
+
 	/* Don't poll the roothubs on bus suspend. */
 	xhci_dbg(xhci, "%s: stopping port polling.\n", __func__);
 	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);