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Subject[PATCH] [90/106] serial/imx: read cts state only after acking cts change irq
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <>

commit 5680e94148a86e8c31fdc5cb0ea0d5c6810c05b0 upstream.

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uart_handle_cts_change is called with a outdated value for cts.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 <>
Tested-by: Arwed Springer <>
Signed-off-by: Uwe Kleine-König <>
Signed-off-by: Greg Kroah-Hartman <>
Signed-off-by: Andi Kleen <>

drivers/serial/imx.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.35.y/drivers/serial/imx.c
--- linux-2.6.35.y.orig/drivers/serial/imx.c
+++ linux-2.6.35.y/drivers/serial/imx.c
@@ -383,12 +383,13 @@ static void imx_start_tx(struct uart_por
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);

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