[PATCH 1/2 bugfix] serial: imx: reset the uart port all the time

[PATCH 1/2 bugfix] serial: imx: reset the uart port all the time

[Huang Shijie]

Current code resets the uart port only when it supports the irda mode.
In actually, we also need to reset the uart port in the non-irda mode.
A hang was caught in the following case:

    UART A transmits data to the other end. But the transmission maybe
    terminated. In some corner case, the TX FIFO maybe not empty.

The kernel will hang at the imx_set_termios():
	............................................................
	while (!(readl(sport->port.membase + USR2) & USR2_TXDC))
		barrier();
	............................................................

This patch resets the uart port all the time in the imx_startup().
And fix the hang.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 drivers/tty/serial/imx.c |   22 ++++++++++------------
 1 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 3b6c1a2..64901d0 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1070,7 +1070,7 @@ static void imx_disable_dma(struct imx_port *sport)
 static int imx_startup(struct uart_port *port)
 {
 	struct imx_port *sport = (struct imx_port *)port;
-	int retval;
+	int retval, i;
 	unsigned long flags, temp;
 
 	retval = clk_prepare_enable(sport->clk_per);
@@ -1098,17 +1098,15 @@ static int imx_startup(struct uart_port *port)
 
 	writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
 
-	if (USE_IRDA(sport)) {
-		/* reset fifo's and state machines */
-		int i = 100;
-		temp = readl(sport->port.membase + UCR2);
-		temp &= ~UCR2_SRST;
-		writel(temp, sport->port.membase + UCR2);
-		while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) &&
-		    (--i > 0)) {
-			udelay(1);
-		}
-	}
+	/* Reset fifo's and state machines */
+	i = 100;
+
+	temp = readl(sport->port.membase + UCR2);
+	temp &= ~UCR2_SRST;
+	writel(temp, sport->port.membase + UCR2);
+
+	while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
+		udelay(1);
 
 	/*
 	 * Allocate the IRQ(s) i.MX1 has three interrupts whereas later
-- 
1.7.8

[PATCH 2/2] serial: imx: remove the redandunt code

[Huang Shijie]

In the imx_startup(), we will reset the uart port which will reset all
the FIFOs, including the URXD.

So the code to clear the RX FIFO is redandunt. Just remove it.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 drivers/tty/serial/imx.c |    9 ---------
 1 files changed, 0 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 64901d0..febf400 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1161,15 +1161,6 @@ static int imx_startup(struct uart_port *port)
 		temp |= UCR2_IRTS;
 	writel(temp, sport->port.membase + UCR2);
 
-	if (USE_IRDA(sport)) {
-		/* clear RX-FIFO */
-		int i = 64;
-		while ((--i > 0) &&
-			(readl(sport->port.membase + URXD0) & URXD_CHARRDY)) {
-			barrier();
-		}
-	}
-
 	if (!is_imx1_uart(sport)) {
 		temp = readl(sport->port.membase + UCR3);
 		temp |= IMX21_UCR3_RXDMUXSEL;
-- 
1.7.8

[PATCH 2/2 v2] serial: imx: remove the redundant code

[Huang Shijie]

In the imx_startup(), we will reset the uart port which will reset all
the FIFOs, including the URXD.

So the code to clear the RX FIFO is redundant. Just remove it.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
fix the typo.
---
 drivers/tty/serial/imx.c |    9 ---------
 1 files changed, 0 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 64901d0..febf400 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1161,15 +1161,6 @@ static int imx_startup(struct uart_port *port)
 		temp |= UCR2_IRTS;
 	writel(temp, sport->port.membase + UCR2);
 
-	if (USE_IRDA(sport)) {
-		/* clear RX-FIFO */
-		int i = 64;
-		while ((--i > 0) &&
-			(readl(sport->port.membase + URXD0) & URXD_CHARRDY)) {
-			barrier();
-		}
-	}
-
 	if (!is_imx1_uart(sport)) {
 		temp = readl(sport->port.membase + UCR3);
 		temp |= IMX21_UCR3_RXDMUXSEL;
-- 
1.7.8