This patch adds some local_irq_{save,restore}() code to usbtty to cope with the
lack of lacking in the case of irq-accelerated usb device drivers (such as our
s3c24xx udc driver).

Index: u-boot/drivers/serial/usbtty.c
===================================================================
--- u-boot.orig/drivers/serial/usbtty.c
+++ u-boot/drivers/serial/usbtty.c
@@ -26,6 +26,7 @@
 #ifdef CONFIG_USB_TTY
 
 #include <asm/io.h>
+#include <asm/proc/system.h>
 #include <circbuf.h>
 #include <devices.h>
 #include "usbtty.h"
@@ -1039,16 +1040,26 @@
 	struct usb_endpoint_instance *endpoint =
 			&endpoint_instance[tx_endpoint];
 	struct urb *current_urb = NULL;
+	unsigned long flags;
 
+	local_irq_save(flags);
 	current_urb = next_urb (device_instance, endpoint);
 	/* TX data still exists - send it now
 	 */
+
+	/* I don't really understand what this logic is supposed to do,
+	 * at least on the s3c24xx usb driver it causes all data to be
+	 * transmitted twice !?! - Harald Welte */
+#if !(defined(CONFIG_S3C2410) || defined(CONFIG_S3C2440) || \
+     defined(CONFIG_S3C2442) || defined(CONFIG_S3C2443))
 	if(endpoint->sent < current_urb->actual_length){
 		if(udc_endpoint_write (endpoint)){
 			/* Write pre-empted by RX */
+			local_irq_restore(flags);
 			return -1;
 		}
 	}
+#endif
 
 	if (buf->size) {
 		char *dest;
@@ -1065,6 +1076,7 @@
 			if (!current_urb) {
 				TTYERR ("current_urb is NULL, buf->size %d\n",
 					buf->size);
+				local_irq_restore(flags);
 				return total;
 			}
 
@@ -1090,14 +1102,17 @@
 			if (endpoint->last == 0) {
 				if(udc_endpoint_write (endpoint)){
 					/* Write pre-empted by RX */
+					local_irq_restore(flags);
 					return -1;
 				}
 			}
 
 		}/* end while */
+		local_irq_restore(flags);
 		return total;
 	}
 
+	local_irq_restore(flags);
 	return 0;
 }
 
@@ -1105,9 +1120,11 @@
 {
 	struct usb_endpoint_instance *endpoint =
 		&endpoint_instance[rx_endpoint];
+	unsigned int nb = 0;
+	unsigned long flags;
 
+	local_irq_save(flags);
 	if (endpoint->rcv_urb && endpoint->rcv_urb->actual_length) {
-		unsigned int nb = 0;
 		char *src = (char *) endpoint->rcv_urb->buffer;
 		unsigned int rx_avail = buf->totalsize - buf->size;
 
@@ -1118,9 +1135,9 @@
 			endpoint->rcv_urb->actual_length = 0;
 
 		}
-		return nb;
 	}
-	return 0;
+	local_irq_restore(flags);
+	return nb;
 }
 
 static int usbtty_configured (void)