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Date:   Mon,  8 Jul 2019 17:12:20 +0200
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Joakim Zhang <>,
        Dong Aisheng <>,
        Marc Kleine-Budde <>
Subject: [PATCH 4.9 027/102] can: flexcan: fix timeout when set small bitrate

From: Joakim Zhang <>

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 =

| root@...6ul7d:~# 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 <>
Reviewed-by: Dong Aisheng <>
Cc: linux-stable <>
Signed-off-by: Marc Kleine-Budde <>
Signed-off-by: Greg Kroah-Hartman <>

 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
@@ -171,7 +171,7 @@
 #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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