tty: xuartps: Improve startup function

The startup function is supposed to initialize the UART for receiving.
Hence, don't enable the TX part. Also, protect HW accesses with the port
lock.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
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 ef114d7..6ffd3bb 100644 (file)
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -758,6 +758,7 @@ static void cdns_uart_set_termios(struct uart_port *port,
  */
 static int cdns_uart_startup(struct uart_port *port)
 {
+       unsigned long flags;
        unsigned int retval = 0, status = 0;
 
        retval = request_irq(port->irq, cdns_uart_isr, 0, CDNS_UART_NAME,
@@ -765,6 +766,8 @@ static int cdns_uart_startup(struct uart_port *port)
        if (retval)
                return retval;
 
+       spin_lock_irqsave(&port->lock, flags);
+
        /* Disable the TX and RX */
        writel(CDNS_UART_CR_TX_DIS | CDNS_UART_CR_RX_DIS,
                        port->membase + CDNS_UART_CR_OFFSET);
@@ -775,15 +778,14 @@ static int cdns_uart_startup(struct uart_port *port)
        writel(CDNS_UART_CR_TXRST | CDNS_UART_CR_RXRST,
                        port->membase + CDNS_UART_CR_OFFSET);
 
-       status = readl(port->membase + CDNS_UART_CR_OFFSET);
-
-       /* Clear the RX disable and TX disable bits and then set the TX enable
-        * bit and RX enable bit to enable the transmitter and receiver.
+       /*
+        * Clear the RX disable bit and then set the RX enable bit to enable
+        * the receiver.
         */
-       writel((status & ~(CDNS_UART_CR_TX_DIS | CDNS_UART_CR_RX_DIS))
-                       | (CDNS_UART_CR_TX_EN | CDNS_UART_CR_RX_EN |
-                       CDNS_UART_CR_STOPBRK),
-                       port->membase + CDNS_UART_CR_OFFSET);
+       status = readl(port->membase + CDNS_UART_CR_OFFSET);
+       status &= CDNS_UART_CR_RX_DIS;
+       status |= CDNS_UART_CR_RX_EN;
+       writel(status, port->membase + CDNS_UART_CR_OFFSET);
 
        /* Set the Mode Register with normal mode,8 data bits,1 stop bit,
         * no parity.
@@ -814,6 +816,8 @@ static int cdns_uart_startup(struct uart_port *port)
                CDNS_UART_IXR_RXTRIG | CDNS_UART_IXR_TOUT,
                port->membase + CDNS_UART_IER_OFFSET);
 
+       spin_unlock_irqrestore(&port->lock, flags);
+
        return retval;
 }