[PATCH] amba-pl010: clear error flags on rx error

The pl010 primecell documentation specifies that an error indicated via RSR
should be cleared by a write to ECR.  We didn't do this, which was causing
errors to be re-reported on every call to pl010_rx_chars().

Doing a write to ECR once we detect an error appears to prevent the ep93xx
console UART driver from going into a mode where it reports "ttyAM0: X
input overrun(s)" every couple of keystrokes.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/serial/amba-pl010.c

@@ -129,6 +129,8 @@ static void pl010_rx_chars(struct uart_port *port)
 		 */
 		rsr = readb(port->membase + UART01x_RSR) | UART_DUMMY_RSR_RX;
 		if (unlikely(rsr & UART01x_RSR_ANY)) {
+			writel(0, port->membase + UART01x_ECR);
+
 			if (rsr & UART01x_RSR_BE) {
 				rsr &= ~(UART01x_RSR_FE | UART01x_RSR_PE);
 				port->icount.brk++;