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linux-imx branch which support CAN-FD on imx8qm

Question asked by Andreas Rehn on Dec 9, 2019
Latest reply on Dec 20, 2019 by gusarambula



we like to use the CAN-FD and if we start the socket without fd on flag, the socket can is working fine.

The setup is a ecu, vector can-case and the imx8qm with bitrate 250k and datarate 500k. we use candump to verify the connection. 


but when we try to start the socket can with "fd on" flag the socket comes up but only a few frames was received and the vector can case says that there are receiving errors on the bus.

a grep over journalctl says: "PRESDIV not the same, may risk transfer errors"

After disconnecting the imx8qm the communication between the ecu and the can case works as expected.


after a while of flexcan driver diffing i found 2 separate workstreams form nxp / freescale side on this driver.


for linux-imx - imx_4.9.88_2.0.0_ga  the code base is different to linux-imx - imx_4.14.98_2.0.0_ga 

so in the last commit of 4.9.88 for the driver MLK-16879-3 can: flexcan: add notes for avaliable fd mode rate combinations there are some notes to hardware limitations.


is this correct and or what do you prefer to use? is the driver in 4.14.98_2.0.0_ga ready to use for CAN-FD with different bit and data rates other then the mentioned in 4.9.88_2.0.0_ga? e.g. bitrate 250k and datarate 500k?


thank you