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

[Lennert Buytenhek <buytenh@wantstofly.org>]

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>

Index: linux-2.6.19-rc5/drivers/serial/amba-pl010.c
===================================================================
--- linux-2.6.19-rc5.orig/drivers/serial/amba-pl010.c
+++ linux-2.6.19-rc5/drivers/serial/amba-pl010.c
@@ -129,6 +129,8 @@ static void pl010_rx_chars(struct uart_p
 		 */
 		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++;
-
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