diff mbox

[2/9] tty: xuartps: Use spinlock to serialize HW access

Message ID 1446596450-20918-3-git-send-email-soren.brinkmann@xilinx.com (mailing list archive)
State New, archived
Headers show

Commit Message

Soren Brinkmann Nov. 4, 2015, 12:20 a.m. UTC 
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>
---
 drivers/tty/serial/xilinx_uartps.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

Comments

kernel test robot Nov. 4, 2015, 12:52 a.m. UTC | #1 
Hi Soren,

[auto build test WARNING on v4.3-rc7]
[also WARNING on: next-20151103]

url:    https://github.com/0day-ci/linux/commits/Soren-Brinkmann/tty-xuartps-Beautify-read-modify-writes/20151104-082546
base:   https://github.com/0day-ci/linux Soren-Brinkmann/tty-xuartps-Beautify-read-modify-writes/20151104-082546
config: i386-allmodconfig (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   drivers/tty/serial/xilinx_uartps.c: In function 'cdns_uart_poll_get_char':
>> drivers/tty/serial/xilinx_uartps.c:948:6: warning: unused variable 'imr' [-Wunused-variable]
     u32 imr;
         ^
   drivers/tty/serial/xilinx_uartps.c: In function 'cdns_uart_poll_put_char':
   drivers/tty/serial/xilinx_uartps.c:968:6: warning: unused variable 'imr' [-Wunused-variable]
     u32 imr;
         ^

vim +/imr +948 drivers/tty/serial/xilinx_uartps.c

19038ad9f Lars-Peter Clausen 2014-11-05  932  
19f22efdb Thomas Betker      2015-03-12  933  	val = readl(port->membase + CDNS_UART_MODEMCR_OFFSET);
19038ad9f Lars-Peter Clausen 2014-11-05  934  
19038ad9f Lars-Peter Clausen 2014-11-05  935  	val &= ~(CDNS_UART_MODEMCR_RTS | CDNS_UART_MODEMCR_DTR);
19038ad9f Lars-Peter Clausen 2014-11-05  936  
19038ad9f Lars-Peter Clausen 2014-11-05  937  	if (mctrl & TIOCM_RTS)
19038ad9f Lars-Peter Clausen 2014-11-05  938  		val |= CDNS_UART_MODEMCR_RTS;
19038ad9f Lars-Peter Clausen 2014-11-05  939  	if (mctrl & TIOCM_DTR)
19038ad9f Lars-Peter Clausen 2014-11-05  940  		val |= CDNS_UART_MODEMCR_DTR;
19038ad9f Lars-Peter Clausen 2014-11-05  941  
19f22efdb Thomas Betker      2015-03-12  942  	writel(val, port->membase + CDNS_UART_MODEMCR_OFFSET);
61ec90169 John Linn          2011-04-30  943  }
61ec90169 John Linn          2011-04-30  944  
6ee04c6c5 Vlad Lungu         2013-10-17  945  #ifdef CONFIG_CONSOLE_POLL
d9bb3fb12 Soren Brinkmann    2014-04-04  946  static int cdns_uart_poll_get_char(struct uart_port *port)
6ee04c6c5 Vlad Lungu         2013-10-17  947  {
6ee04c6c5 Vlad Lungu         2013-10-17 @948  	u32 imr;
6ee04c6c5 Vlad Lungu         2013-10-17  949  	int c;
c2fd7b9d5 Soren Brinkmann    2015-11-03  950  	unsigned long flags;
6ee04c6c5 Vlad Lungu         2013-10-17  951  
c2fd7b9d5 Soren Brinkmann    2015-11-03  952  	spin_lock_irqsave(&port->lock, flags);
6ee04c6c5 Vlad Lungu         2013-10-17  953  
6ee04c6c5 Vlad Lungu         2013-10-17  954  	/* Check if FIFO is empty */
19f22efdb Thomas Betker      2015-03-12  955  	if (readl(port->membase + CDNS_UART_SR_OFFSET) & CDNS_UART_SR_RXEMPTY)
6ee04c6c5 Vlad Lungu         2013-10-17  956  		c = NO_POLL_CHAR;

:::::: The code at line 948 was first introduced by commit
:::::: 6ee04c6c5488b2b7fdfa22c771c127411f86e610 tty: xuartps: Add polled mode support for xuartps

:::::: TO: Vlad Lungu <vlad.lungu@windriver.com>
:::::: CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
diff mbox

Patch

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 50d4082d2354..dc1987f3dc0a 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -947,10 +947,9 @@  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)
@@ -959,8 +958,7 @@  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;
 }
@@ -968,10 +966,9 @@  static int cdns_uart_poll_get_char(struct uart_port *port)
 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 +983,7 @@  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;
 }