refine xhci-plat-Fix-xhci_plat-shutdown-sequence

[leiwan@codeaurora.org]

xhci-plat Shutdown callback should check HCD_FLAG_HW_ACCESSIBLE
before accessing any register. This should avoid hung with access
controllers which support runtime suspend

This can fix for issue of https://patchwork.kernel.org/patch/10339317/
corresponding upload in CAF:
https://source.codeaurora.org/quic/la/kernel/msm-4.4/commit/?h=LV.HB.1.1.5-03810-8x96.0&id=a7a5307ee04ad349d365ad50f304605a9cd9bd0a

full patch refer attachment.

From 9b65acb64f1ad87d115fa147c9e947fb3d37471c Mon Sep 17 00:00:00 2001
From: Lei wang <leiwan@codeaurora.org>
Date: Tue, 17 Apr 2018 10:55:35 +0800
Subject: [PATCH] xhci: plat: Fix xhci_plat shutdown hung

xhci-plat Shutdown callback should check HCD_FLAG_HW_ACCESSIBLE
before accessing any register. This should avoid hung with access
controllers which support runtime suspend

Signed-off-by: Lei wang <leiwan@codeaurora.org>
---
 drivers/usb/host/xhci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 9b27798..bdf914d 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -702,6 +702,10 @@ static void xhci_shutdown(struct usb_hcd *hcd)
 		usb_disable_xhci_ports(to_pci_dev(hcd->self.sysdev));
 
 	spin_lock_irq(&xhci->lock);
+	if (!HCD_HW_ACCESSIBLE(hcd)) {
+		spin_unlock_irq(&xhci->lock);
+		return;
+	}
 	xhci_halt(xhci);
 	/* Workaround for spurious wakeups at shutdown with HSW */
 	if (xhci->quirks & XHCI_SPURIOUS_WAKEUP)
-- 
1.9.1