[PATCH 2/9] tty: xuartps: Use spinlock to serialize HW access
From: Soren Brinkmann <hidden>
Date: 2015-11-04 00:23:10
Also in:
linux-serial, lkml
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
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 <redacted> --- drivers/tty/serial/xilinx_uartps.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)
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; }
--
2.6.2.3.ga463a5b