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    Subject[34-longterm 092/196] serial/imx: read cts state only after acking cts change irq
    Date
    From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
    -------------------

    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    uart_handle_cts_change is called with a outdated value for cts.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)

    [PG: file in drivers/serial not drivers/tty/serial in .34]

    Reported-by: Arwed Springer <Arwed.Springer@de.trumpf.com>
    Tested-by: Arwed Springer <Arwed.Springer@de.trumpf.com>
    Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    drivers/serial/imx.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c
    index eacb588..6d2028e 100644
    --- a/drivers/serial/imx.c
    +++ b/drivers/serial/imx.c
    @@ -383,12 +383,13 @@ 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);

    --
    1.7.9.3
    --
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