From 697beb0b85aca54f9d09df20b5228c16c6563edb Mon Sep 17 00:00:00 2001
From: Anton Vorontsov <anton.vorontsov@linaro.org>
Date: Mon, 24 Sep 2012 14:27:55 -0700
Subject: [PATCH] --- yaml --- r: 325796 b: refs/heads/master c:
 5c8124a0f8f50c5671b028b7a030d893a3a1a539 h: refs/heads/master v: v3

---
 [refs]                                |  2 +-
 trunk/drivers/tty/serial/amba-pl011.c | 29 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index ea005e5fae89..d551a417628b 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b3564c2cf464e11f8cb4f8d9c124e5e0f5418e3f
+refs/heads/master: 5c8124a0f8f50c5671b028b7a030d893a3a1a539
diff --git a/trunk/drivers/tty/serial/amba-pl011.c b/trunk/drivers/tty/serial/amba-pl011.c
index ea7aa973ab43..d7e1edec50b5 100644
--- a/trunk/drivers/tty/serial/amba-pl011.c
+++ b/trunk/drivers/tty/serial/amba-pl011.c
@@ -1284,11 +1284,40 @@ static void pl011_break_ctl(struct uart_port *port, int break_state)
 }
 
 #ifdef CONFIG_CONSOLE_POLL
+
+static void pl011_quiesce_irqs(struct uart_port *port)
+{
+	struct uart_amba_port *uap = (struct uart_amba_port *)port;
+	unsigned char __iomem *regs = uap->port.membase;
+
+	writew(readw(regs + UART011_MIS), regs + UART011_ICR);
+	/*
+	 * There is no way to clear TXIM as this is "ready to transmit IRQ", so
+	 * we simply mask it. start_tx() will unmask it.
+	 *
+	 * Note we can race with start_tx(), and if the race happens, the
+	 * polling user might get another interrupt just after we clear it.
+	 * But it should be OK and can happen even w/o the race, e.g.
+	 * controller immediately got some new data and raised the IRQ.
+	 *
+	 * And whoever uses polling routines assumes that it manages the device
+	 * (including tx queue), so we're also fine with start_tx()'s caller
+	 * side.
+	 */
+	writew(readw(regs + UART011_IMSC) & ~UART011_TXIM, regs + UART011_IMSC);
+}
+
 static int pl011_get_poll_char(struct uart_port *port)
 {
 	struct uart_amba_port *uap = (struct uart_amba_port *)port;
 	unsigned int status;
 
+	/*
+	 * The caller might need IRQs lowered, e.g. if used with KDB NMI
+	 * debugger.
+	 */
+	pl011_quiesce_irqs(port);
+
 	status = readw(uap->port.membase + UART01x_FR);
 	if (status & UART01x_FR_RXFE)
 		return NO_POLL_CHAR;