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J784S4XEVM: MCAN4 disabled in SDK 10.01

Minh Nguyen
Prodigy 100 points
Part Number: J784S4XEVM

Tool/software:

Hi Ti experts,

I want to enable MCAN3,4 and 5 which are disabed by default in SDK 10.01. I noticed that MCAN4 controls a common standby signal shared with MCAN 3 and MCAN 5 in k3-j784s4-evm-ethfw.dtso. After enabling MCAN4 in te ETHFW DTBO, all MCAN3,4 and 5 are working as expected. But I am worrying about the following comments

"Disable the following to avoid overloading exp2" in the ETHFW DTBO as shown below

/*
 * Disable the following to avoid overloading exp2.
 * Otherwise it will result in PHY read/write errors.
 */
&main_mcan4 {
	status = "disabled";
};

&transceiver3 {
	status = "disabled";
};

&mux1 {
	status = "disabled";
};

Here are my question regarding the above comments


1. Why does enabling MCAN4 cause overloading EXP2?

2. Can you explain why it happens when enabling MCAN4?

3. I do no use ETHFW by disabling it when compiling vision_apps firmware. Will the EXP2 be overloading with MCAN4 enabled and ETHFW disabled?

Thanks,

Minh

  • 0
    TI__Guru 50823 points

    Hi Minh,

    Let me double check with the team on that comment, as I do not have the context. 

    However, to give a guess... if ETHFW is disabled, then I have doubts there will be issues with MCAN4. From schematics, MCAN4 is almost a direct connection from SoC to MCAN transceiver (although there is a mux in between). There is routing to an optional GESI expansion daughter card for ethernet, but if this is not used, then it can be ignored. Also, default devicetree file for EVM enables main MCAN4 interface, so it should be functional.

    Regards,

    Takuma

  • 0 in reply to Takuma Fujiwara
    Prodigy 100 points

    Hi Takuma,

    It is true that default device tree enables MCAN4. However, prebuilt SDK 10.01 image enables ETHFW DTBO in uEnv.txt which is disabled MCAN4.

    # Setting the right U-Boot environment variables
dorprocboot=1
name_overlays=ti/k3-j784s4-evm-ethfw.dtbo ti/k3-j784s4-vision-apps.dtbo

    As a result MCAN3 and MCAN5 are also disabled due to shared standby signal from MCAN4 node  does not pull to logic low.

    I am still waiting for answer about EXP2 overloading when enabling MCAN4.

  • 0 in reply to Minh Nguyen
    TI__Guru 50823 points

    Hi Minh,

    Could I get 1~2 business days? Currently checking with the commit author on this.

    Regards,

    Takuma 

  • 0 in reply to Takuma Fujiwara
    Prodigy 100 points

    Sure. Let me know when you get answer from the commit author.

  • 0 in reply to Minh Nguyen
    TI__Guru 50823 points

    Hi Minh,

    For your case, the comment for exp2 being overloaded can be ignored. 

    The issue occurs when EthFw is enabled. This is because the i2c bus leading to the expansion is shared between MCAN4 and EthFw, and having both enabled will cause problems if they concurrently attempt to access the i2c bus. MCAN is enabled in Linux on the A72 core while EthFw runs on a different core running RTOS. Therefore, we cannot prevent concurrent accesses from software and hence MCAN4 is disabled in the EthFw overlay.

    Therefore, MCAN4 will remain functional for the use-case where EthFw is unused.

    Regards,

    Takuma

  • 0 in reply to Takuma Fujiwara
    Prodigy 100 points

    Thanks Takuma for the clarification.

    Minh