can: flexcan: fix timeout when set small bitrate

commit 247e535 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 <[email protected]>
Reviewed-by: Dong Aisheng <[email protected]>
Cc: linux-stable <[email protected]>
Signed-off-by: Marc Kleine-Budde <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Joakim Zhang

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
  *