xhci: Convert xhci_handshake() to use readl_poll_timeout_atomic()

Xhci_handshake() implements the algorithm already captured by
readl_poll_timeout_atomic(). Convert the former to use the latter to
avoid repetition.

Turned out this patch also fixes a bug on the AMD Stoneyridge platform
where usleep(1) sometimes takes over 10ms.
This means a 5 second timeout can easily take over 15 seconds which will
trigger the watchdog and reboot the system.

[Add info about patch fixing a bug to commit message -Mathias]
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Tested-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-by: Raul E Rangel <rrangel@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.c

@@ -9,6 +9,7 @@
  */
 
 #include <linux/pci.h>
+#include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/log2.h>
 #include <linux/module.h>
@@ -52,7 +53,6 @@ static bool td_on_ring(struct xhci_td *td, struct xhci_ring *ring)
 	return false;
 }
 
-/* TODO: copied from ehci-hcd.c - can this be refactored? */
 /*
  * xhci_handshake - spin reading hc until handshake completes or fails
  * @ptr: address of hc register to be read
@@ -69,18 +69,16 @@ static bool td_on_ring(struct xhci_td *td, struct xhci_ring *ring)
 int xhci_handshake(void __iomem *ptr, u32 mask, u32 done, int usec)
 {
 	u32	result;
+	int	ret;
 
-	do {
-		result = readl(ptr);
-		if (result == ~(u32)0)		/* card removed */
-			return -ENODEV;
-		result &= mask;
-		if (result == done)
-			return 0;
-		udelay(1);
-		usec--;
-	} while (usec > 0);
-	return -ETIMEDOUT;
+	ret = readl_poll_timeout_atomic(ptr, result,
+					(result & mask) == done ||
+					result == U32_MAX,
+					1, usec);
+	if (result == U32_MAX)		/* card removed */
+		return -ENODEV;
+
+	return ret;
 }
 
 /*