imx6 UART issue on 5.4.24 kernel

[zc_tee]

Hi all,

I am porting my I.MX6 platform kernel from 4.9.11 to 5.4.24, and face some weird issue on the UART port

after i port the code and my device tree, I manage to boot up my machine. Then I tried to read some data from another subcpu which is connected to ttymxc2. 

In console, I tried to cat /dev/ttymxc2, but it returns me with some text that seems like system related information as below:

I tried to do a stty then cat, it returns me with another type of information, which seems to be like cat /proc/filesystems plus something else as below:

I cannot understand why is this happening. It seems like the ttymxc device is mixed up with /proc/ information. Can anybody advise? 

One thing is that the system is working fine in kernel 4.9.11. Only change is changing the kernel from 4.9.11 to 5.4.24.

By the way, i am using same bootloader 2017.03 for both the 4.9.11 and 5.4.24 kernel. I suppose 5.4.24 kernel can work well with 2017.03 uboot?

Thank you.

Regards,

Tee

[igorpadykov]

Hi Tee

you are right, reason may be in uboot, recommended to use

uboot version (v2020.04) as listed in Release Notes of each BSP described on

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

https://source.codeaurora.org/external/imx/uboot-imx/tree/?h=imx_v2020.04_5.4.24_2.1.0

Best regards
igor

[zc_tee]

Hi Igor,

After doing some searching online, i tried to disable the serial port dma in device tree

Then my machine's UART port works.

I think i will disable the UART dma for now and test further. Do you forsee any issue disabling the UART's dma?

Regards,

Tee

[igorpadykov · Accepted solution]

Hi Tee

usually dma is disabled for console port.

Best regards
igor

[zc_tee]

Hi Igor

Thank you. I will proceed with disabling UART dma.