tty: xuartps: Use spinlock to serialize HW access

Instead of disabling the IRQ, use the spin lock to serialize accesses to
the HW. This protects the driver from interference of non-IRQ callbacks
with each other and makes the driver more consistent in its
serialization method.

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 50d4082d2354c007af44a9f58d01998ddb1a375b..2c98c357d9a09390ed0c3d6e22b900ee9f496890 100644 (file)
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -945,12 +945,10 @@ static void cdns_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 #ifdef CONFIG_CONSOLE_POLL
 static int cdns_uart_poll_get_char(struct uart_port *port)
 {
-       u32 imr;
        int c;
+       unsigned long flags;
 
-       /* Disable all interrupts */
-       imr = readl(port->membase + CDNS_UART_IMR_OFFSET);
-       writel(imr, port->membase + CDNS_UART_IDR_OFFSET);
+       spin_lock_irqsave(&port->lock, flags);
 
        /* Check if FIFO is empty */
        if (readl(port->membase + CDNS_UART_SR_OFFSET) & CDNS_UART_SR_RXEMPTY)
@@ -959,19 +957,16 @@ static int cdns_uart_poll_get_char(struct uart_port *port)
                c = (unsigned char) readl(
                                        port->membase + CDNS_UART_FIFO_OFFSET);
 
-       /* Enable interrupts */
-       writel(imr, port->membase + CDNS_UART_IER_OFFSET);
+       spin_unlock_irqrestore(&port->lock, flags);
 
        return c;
 }
 
 static void cdns_uart_poll_put_char(struct uart_port *port, unsigned char c)
 {
-       u32 imr;
+       unsigned long flags;
 
-       /* Disable all interrupts */
-       imr = readl(port->membase + CDNS_UART_IMR_OFFSET);
-       writel(imr, port->membase + CDNS_UART_IDR_OFFSET);
+       spin_lock_irqsave(&port->lock, flags);
 
        /* Wait until FIFO is empty */
        while (!(readl(port->membase + CDNS_UART_SR_OFFSET) &
@@ -986,8 +981,7 @@ static void cdns_uart_poll_put_char(struct uart_port *port, unsigned char c)
                                CDNS_UART_SR_TXEMPTY))
                cpu_relax();
 
-       /* Enable interrupts */
-       writel(imr, port->membase + CDNS_UART_IER_OFFSET);
+       spin_unlock_irqrestore(&port->lock, flags);
 
        return;
 }