From 18639db64ff6585d4be91f9645674957feb01452 Mon Sep 17 00:00:00 2001
From: Matson Hall <matson.hall@gmail.com>
Date: Wed, 26 Sep 2012 15:23:20 +0200
Subject: [PATCH] tty: sunxi-8250: fix something in the hackery with more
 hackery

---
 drivers/tty/serial/8250/8250.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
index ef5bcd957ae25a..d6daf8ff07227b 100644
--- a/drivers/tty/serial/8250/8250.c
+++ b/drivers/tty/serial/8250/8250.c
@@ -1524,9 +1524,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 	struct uart_8250_port *up =
 		container_of(port, struct uart_8250_port, port);
 
-	if (iir & UART_IIR_NO_INT)
-		return 0;
-
+	if (! (iir & UART_IIR_NO_INT)) {
 	spin_lock_irqsave(&port->lock, flags);
 
 	status = serial_port_in(port, UART_LSR);
@@ -1541,6 +1539,25 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 	spin_unlock_irqrestore(&port->lock, flags);
 	return 1;
+	} else if ((up->port.iotype == UPIO_MEM32) &&
+		  (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
+		/* The DesignWare APB UART has an Busy Detect (0x07)
+		 * interrupt meaning an LCR write attempt occurred while the
+		 * UART was busy. The interrupt must be cleared by reading
+		 * the UART status register (USR) and the LCR re-written. */
+		unsigned int mcr_t = serial_in(up, UART_MCR);
+		printk(">>> ttyS%d bus busy...\n", up->port.line);
+		//status = *(volatile u32 *)up->port.private_data;
+		serial_out(up, UART_MCR, mcr_t|(1<<4)); //to loopback mode
+		while(serial_in(up, UART_USR)&1)
+			serial_in(up, UART_RX);
+		serial_out(up, UART_LCR, up->lcr);
+		serial_out(up, UART_MCR, mcr_t);    //to normal mode
+
+		return 1;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(serial8250_handle_irq);