Xilinx: ARM: UART: clear pending irqs before enabling irqs

The Boot ROM has an issue which will cause the driver to
lock up as pending irqs are not being cleared. With them
cleared it prevents that issue.

This patch is needed for the current (3.9-rc3) mainline kernel. I guess
it went unnoticed, because it was only tested with u-boot up until now.
And u-boot maybe handles this.

[s.trumtrar@pengutronix.de: cherry-picked from linux-xlnx.git]
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index ba451c7209fc6b9bbaaf47b9e2d2458f202feaf8..f36bbba1ac8b9070cc7cefafb8a33265a7872253 100644 (file)
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -578,6 +578,8 @@ static int xuartps_startup(struct uart_port *port)
        /* Receive Timeout register is enabled with value of 10 */
        xuartps_writel(10, XUARTPS_RXTOUT_OFFSET);
 
+       /* Clear out any pending interrupts before enabling them */
+       xuartps_writel(xuartps_readl(XUARTPS_ISR_OFFSET), XUARTPS_ISR_OFFSET);
 
        /* Set the Interrupt Registers with desired interrupts */
        xuartps_writel(XUARTPS_IXR_TXEMPTY | XUARTPS_IXR_PARITY |