From: Soren Brinkmann <soren.brinkmann@xilinx.com>
Date: Sat, 26 Dec 2015 10:43:50 +0000 (-0800)
Subject: tty: xuartps: Use spinlock to serialize HW access
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=f0f54a806b2df97485519a7c4ebc45feed08a306;p=openwrt%2Fstaging%2Fblogic.git

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 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;
 }