[PATCH 1/1] serial: mcf: Don't take spinlocks in already protected functions

ygeorgie
2010-06-09T07:56:45Z

From: Yury Georgievskiy <ygeorgie@gmail.com>

Don't take the port spinlock in uart functions where the serial core
already takes care of locking/unlocking them.

The code would actually lock up on architectures where spinlocks are
implemented.

Also protect calling mcf_rx_chars/mcf_tx_chars in the
interrupt handler by the port spinlock and use IRQ_RETVAL
to return from isr.

Signed-off-by: Yury Georgievskiy <ygeorgie@gmail.com>
---
drivers/serial/mcf.c | 22 ++++++----------------
1 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/serial/mcf.c b/drivers/serial/mcf.c
index b5aaef9..6235444 100644
--- a/drivers/serial/mcf.c
+++ b/drivers/serial/mcf.c
@@ -70,16 +70,14 @@ static unsigned int mcf_tx_empty(struct uart_port *port)
static unsigned int mcf_get_mctrl(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
- unsigned long flags;
unsigned int sigs;

- spin_lock_irqsave(&port->lock, flags);
sigs = (readb(port->membase + MCFUART_UIPR) & MCFUART_UIPR_CTS) ?
0 : TIOCM_CTS;
sigs |= (pp->sigs & TIOCM_RTS);
sigs |= (mcf_getppdcd(port->line) ? TIOCM_CD : 0);
sigs |= (mcf_getppdtr(port->line) ? TIOCM_DTR : 0);
- spin_unlock_irqrestore(&port->lock, flags);
+
return sigs;
}

@@ -88,16 +86,13 @@ static unsigned int mcf_get_mctrl(struct uart_port *port)
static void mcf_set_mctrl(struct uart_port *port, unsigned int sigs)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
- unsigned long flags;

- spin_lock_irqsave(&port->lock, flags);
pp->sigs = sigs;
mcf_setppdtr(port->line, (sigs & TIOCM_DTR));
if (sigs & TIOCM_RTS)
writeb(MCFUART_UOP_RTS, port->membase + MCFUART_UOP1);
else
writeb(MCFUART_UOP_RTS, port->membase + MCFUART_UOP0);
- spin_unlock_irqrestore(&port->lock, flags);
}

/****************************************************************************/
@@ -105,12 +100,9 @@ static void mcf_set_mctrl(struct uart_port *port, unsigned int sigs)
static void mcf_start_tx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
- unsigned long flags;

- spin_lock_irqsave(&port->lock, flags);
pp->imr |= MCFUART_UIR_TXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
- spin_unlock_irqrestore(&port->lock, flags);
}

/****************************************************************************/
@@ -118,12 +110,9 @@ static void mcf_start_tx(struct uart_port *port)
static void mcf_stop_tx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
- unsigned long flags;

- spin_lock_irqsave(&port->lock, flags);
pp->imr &= ~MCFUART_UIR_TXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
- spin_unlock_irqrestore(&port->lock, flags);
}

/****************************************************************************/
@@ -131,12 +120,9 @@ static void mcf_stop_tx(struct uart_port *port)
static void mcf_stop_rx(struct uart_port *port)
{
struct mcf_uart *pp = container_of(port, struct mcf_uart, port);
- unsigned long flags;

- spin_lock_irqsave(&port->lock, flags);
pp->imr &= ~MCFUART_UIR_RXREADY;
writeb(pp->imr, port->membase + MCFUART_UIMR);
- spin_unlock_irqrestore(&port->lock, flags);
}

/****************************************************************************/
@@ -368,11 +354,15 @@ static irqreturn_t mcf_interrupt(int irq, void *data)
unsigned int isr;

isr = readb(port->membase + MCFUART_UISR) & pp->imr;
+
+ spin_lock(&port->lock);
if (isr & MCFUART_UIR_RXREADY)
mcf_rx_chars(pp);
if (isr & MCFUART_UIR_TXREADY)
mcf_tx_chars(pp);
- return IRQ_HANDLED;
+ spin_unlock(&port->lock);
+
+ return IRQ_RETVAL(isr);
}

/****************************************************************************/
--
1.7.0