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    Subject[PATCH 5.1 094/121] can: flexcan: fix timeout when set small bitrate
    Date
    From: Joakim Zhang <qiangqing.zhang@nxp.com>

    commit 247e5356a709eb49a0d95ff2a7f07dac05c8252c upstream.

    Current we can meet timeout issue when setting a small bitrate like
    10000 as follows on i.MX6UL EVK board (ipg clock = 66MHZ, per clock =
    30MHZ):

    | root@imx6ul7d:~# ip link set can0 up type can bitrate 10000

    A link change request failed with some changes committed already.
    Interface can0 may have been left with an inconsistent configuration,
    please check.

    | RTNETLINK answers: Connection timed out

    It is caused by calling of flexcan_chip_unfreeze() timeout.

    Originally the code is using usleep_range(10, 20) for unfreeze
    operation, but the patch (8badd65 can: flexcan: avoid calling
    usleep_range from interrupt context) changed it into udelay(10) which is
    only a half delay of before, there're also some other delay changes.

    After double to FLEXCAN_TIMEOUT_US to 100 can fix the issue.

    Meanwhile, Rasmus Villemoes reported that even with a timeout of 100,
    flexcan_probe() fails on the MPC8309, which requires a value of at least
    140 to work reliably. 250 works for everyone.

    Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
    Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
    Cc: linux-stable <stable@vger.kernel.org>
    Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/net/can/flexcan.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/net/can/flexcan.c
    +++ b/drivers/net/can/flexcan.c
    @@ -166,7 +166,7 @@
    #define FLEXCAN_MB_CNT_LENGTH(x) (((x) & 0xf) << 16)
    #define FLEXCAN_MB_CNT_TIMESTAMP(x) ((x) & 0xffff)

    -#define FLEXCAN_TIMEOUT_US (50)
    +#define FLEXCAN_TIMEOUT_US (250)

    /* FLEXCAN hardware feature flags
    *

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