drivers: usb: fsl: Workaround for Erratum A004477

Add a delay of 1 microsecond before issuing soft reset to the
controller to let ongoing ULPI transaction complete.
This prevents corruption of ULPI Function Control Register which
eventually prevents phy clock from entering to low power mode

Signed-off-by: Nikhil Badola <nikhil.badola@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

drivers/usb/host/ehci-fsl.c

@@ -138,6 +138,16 @@ int ehci_hcd_init(int index, enum usb_init_type init,
 	if (has_erratum_a007798())
 		set_txfifothresh(ehci, TXFIFOTHRESH);
 
+	if (has_erratum_a004477()) {
+		/*
+		 * When reset is issued while any ULPI transaction is ongoing
+		 * then it may result to corruption of ULPI Function Control
+		 * Register which eventually causes phy clock to enter low
+		 * power mode which stops the clock. Thus delay is required
+		 * before reset to let ongoing ULPI transaction complete.
+		 */
+		udelay(1);
+	}
 	return 0;
 }