MX53 FlexCAN bitrate setting

[frankchenmh]

Hi, I got a problem on MX53 CAN bitrate setting. It seems the bitrate can not be set. I tried "canconfig" but got following result:

# canconfig can0 bitrate 125000

RTNETLINK answers: Operation not supported

failed to set bitrate of can0 to 125000

When I ran "cat /sys/devices/platform/FlexCAN.0/bitrate", it said the bitrate is 282240. But this number looks like not a "standard" number.

When I connect two MX53 boards and run candump on one of the board, run cansend on another board, the test succeeded. But this works only between two MX53 boards.

I tried to set bitrate by "echo 125000 > /sys/devices/platform/FlexCAN.0/bitrate". I watched the waveform by an oscilloscope and found the bitrate did not change.

Is there any way for changing the bitrate of MX53 CAN?

The BSP I used is MX53 Android R10.3. The board is custom board based on MX53-SMD.

Thanks.

[lategoodbye]

Hello Frank,

i don't know much about Android, but under Linux changing the CAN bitrate requires the package iproute2. The necessary call is:

ip link set can0 type can bitrate 125000

For Linux + CAN specific questions their is also a mailing list with an archive:

http://vger.kernel.org/vger-lists.html#linux-can

[frankchenmh]

Hi Stefan,

Thanks for reply.

I tried the "ip" command but got error messages:

root@freescale ~$ ip link set can0 type can bitrate 125000

ip: either "dev" is duplicate, or "type" is garbage

By Google it is because the "ip" command is an applet of busybox and it doesn't work.

Then I downloaded and cross-compiled the iproute2 package and got the following message:

root@freescale ~$ /ip link set can0 type can bitrate 125000

RTNETLINK answers: Operation not supported

So the error is similar to canconfig. I guess there may be something wrong in kernel/driver configuration.

Does FSL or FSL customer have successful experience in setting MX53 CAN bitrate?

The above tests were performed on Linux.

[shanegrif]

Did you manage to resolve this problem? I'm seeing something very similar.

[frankchenmh]

Hi Shane,

Yes, I have resolved the problem. We can use the CAN sysfs attribute to change the bitrate, for example:

"echo 125000 > /sys/devices/platform/FlexCAN.0/bitrate"

However, the clock setting for MX53 CAN is incorrect in MX53 Android release R10.3. To fix this problem, please refer to the following link:

https://community.freescale.com/message/358164#358164

[santhoshkarthik]

Dear Frank,

   I have the same problem in setting bitrate in CAN using FlexCAN driver.  I did same thing as you said

root@mx28evk ~$ ip link set can0 type can bitrate 125000
RTNETLINK answers: Operation not supported
root@mx28evk ~$ ip link set can0 type can bitrate 125000
RTNETLINK answers: Operation not supported
root@mx28evk ~$ echo 125000 > /sys/devices/platform/FlexCAN.0/bitrate
root@mx28evk ~$ cat /sys/devices/platform/FlexCAN.0/bitrate
500000
root@mx28evk ~$

   but bitrate is not getting changed even after writing into CAN sysfs attribute. Please help me to resolve this issue and let me know what are the things I have to change in kernel menuconfig.

 Note : I am working on imx28 EVK board with Linux 2.6.35.

[shanegrif]

Frank,

Thanks for reply. I think I'm seeing something different. I already made the changes to fix the parent clock issue, although in our case, we're using the IPG clock (running at 66MHz). When I made this change, the baud rate measured on the scope matched the current setting.

I get an error msg when I use the sysfs method to set the baud rate:

The bitrate 125000 can't supported with clock rate of 66666666.

When I tried canconfig, I got the same error msg that you originally saw. Did you ever get canconfig to work for you?

We're using Android R10.2 for iMX53 ARD.

Regards,

Shane.

[frankchenmh]

Hi Shane,

No, canconfig didn't work for me. I use sysfs method to changed the bitrate.

I didn't see the error like what you got when use sysfs to changed the bitrate. Perhaps it is because the BSP versions we used are different. The BSP I worked on is MX53 SMD Android R10.3.

[shanegrif]

Frank,

Just reporting back for completeness, in case anyone else runs into this problem.

I changed my code to use the LP_APM clock as the parent clock for the CAN modules, and I can now set the baud rate using the sysfs method. Looks like this is the default clock in the BSP, so using the IPG clock was a bad idea.

Thanks for your help,

Shane.