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serial/imx: read cts state only after acking cts change irq

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If cts changes between reading the level at the cts input (USR1_RTSS)
and acking the irq (USR1_RTSD) the last edge doesn't generate an irq and
uart_handle_cts_change is called with a outdated value for cts.

The race was introduced by commit

	ceca629 ([ARM] 2971/1: i.MX uart handle rts irq)

Reported-by: Arwed Springer <Arwed.Springer@de.trumpf.com>
Tested-by: Arwed Springer <Arwed.Springer@de.trumpf.com>
Cc: stable@kernel.org # 2.6.14+
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Uwe Kleine-König 2011-04-11 10:59:09 +02:00 committed by Greg Kroah-Hartman
parent 0f6db2172f
commit 5680e94148
1 changed files with 2 additions and 1 deletions
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3
drivers/tty/serial/imx.c
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@ -382,12 +382,13 @@ static void imx_start_tx(struct uart_port *port)
static irqreturn_t imx_rtsint(int irq, void *dev_id)
{
struct imx_port *sport = dev_id;
unsigned int val = readl(sport->port.membase + USR1) & USR1_RTSS;
unsigned int val;
unsigned long flags;
spin_lock_irqsave(&sport->port.lock, flags);
writel(USR1_RTSD, sport->port.membase + USR1);
val = readl(sport->port.membase + USR1) & USR1_RTSS;
uart_handle_cts_change(&sport->port, !!val);
wake_up_interruptible(&sport->port.state->port.delta_msr_wait);