[PATH RESEND v2 02/10] tty: xuartps: Use spinlock to serialize HW access

[Soren Brinkmann]

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.brinkm...@xilinx.com>
---
v2:
 - remove unused variable
---
 drivers/tty/serial/xilinx_uartps.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c 
b/drivers/tty/serial/xilinx_uartps.c
index 50d4082d2354..2c98c357d9a0 100644
--- 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;
 }
-- 
2.6.3.3.g9bb996a

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