Missing ttymxc1 on iMX6ULL

[zmagday]

I built image file for imx6ull using yocto project.

Settings are:

MACHINE = imx6ull14x14evk
DISTRO = fsl-imx-wayland

Image name is "core-image-base".

After downloading the image core-image-base-imx6ull14x14evk-20231019085452.rootfs.wic.zst on the board, I cannot find the /dev/ttymxc1. I need this to use UART2 pins.

Is there any step I should do in building the image to make sure UART2 (ttymxc1) is enabled?

[Dhruvit · Accepted solution]

Hi @zmagday,

I hope you are doing well.

In i.mx6ul EVK uart2 is used by the bluetooth driver, hence ttymxc1 is not generated.

Please try removing below node from uart2 in /arch/arm/boot/dts/imx6ul-14x14-evk.dtsi.

bluetooth {
       compatible = "nxp,88w8987-bt";
};

Thanks & Regards,
Dhruvit Vasavada

[zmagday]

Hi @Dhruvit ,

I used the i.MX Yocto Project User's guide to build image.

Can I edit the dts file prior to building image using bitbake?

I cannot find this file on the build directory.

Do I need to use devtool to edit the device tree?

[Dhruvit]

Hi @zmagday,

I hope you are doing well.

dts file can be found at /build/tmp/work/<platfrom>-poky-linux/linux-imx/<git version>/git/arch/arm/boot/dts/

One can use devtool or devshell to edit this file.

Thanks & Regards,
Dhruvit Vasavada

[zmagday]

I edited the file and commented out the bluetooth for uart2.

But /dev/ttymxc1 is still not available.

I also tried using the devtool, I used the following procedure.

1. devtool modify linux-imx 

2. modify the device tree (<build dir>/workspace/workspace/sources/linux-imx/arch/arm/boot/dts/imx6ul-14x14-evk.dtsi)

3. devtool build-image core-image-base

After doing the steps mentioned, I got this prompt:

Skipping recipe linux-imx as it doesn't produce a package with the same name

I always do bitbake -c clean core-image-base before doing another build.

[Dhruvit]

Hi @zmagday,

I hope you are doing well.

It seems that your changes are not reflected in your final build.

Please refer to 2.4 Using devtool to Patch the Kernel to make changes in linux-imx.

I was able to generate ttymxc1 on i.MX6ULL EVK by removing bluetooth node.

Thanks & Regards,
Dhruvit Vasavada

[zmagday]

Hi @Dhruvit 

I am able to reflect the changes on my image by doing the following.

Without using devtool, I modified this dts file:
<build dir>/tmp/work-shared/imx6ull14x14evk/kernel-source/arch/arm/boot/dts/imx6ul-14x14-evk.dtsi

The I recompiled and deployed using bitbake:
>> bitbake -c compile -f linux-imx
>> bitbake -c deploy linux-imx

After the compile and deploy, I built the image using bitbake.

Thank you very much for your help.

[Dhruvit]

Hi @zmagday,

If this issue is resolved, Please mark this case as solved.

Thanks & Regards,
Dhruvit Vasavada