When we use UART4 on IMX8MM form Linux User Space, device will be kernel panic.

[charleshuang]

Hi NXP Team

In Yocto 4.0 5.15.52.  Device is iMX8MM.

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/How-to-use-UART4-on-iMX8M-from-Linux-Use...

Our customer and My team follow the nxp solution to try use the UART4 on iMX8MM form Linux user space.

But device will be kernel panic.

https://github.com/ADVANTECH-Corp/meta-advantech2/commit/7acd89522542ba2bacdf94121361b140d9ee3793

https://github.com/ADVANTECH-Corp/meta-advantech2/commit/1ff67f71a5eb40fe35e902ce52ec59e8b504413a

About the UART4.

Yocto 3.0 is Pass, but Yocto 4.0_5.15.52 is kernel panic.

Do you have any advice?

 

[Chirag]

Hello,

I am also running into exact same problem. I am on kernel 6.1.22 [imx8mm]. I have build custom imx-boot with updated changes of uart4 in imx-atf firmware as described here
https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/How-to-use-UART4-on-iMX8M-from-Linux-Use...
Although its still not working and having a kernel panic error.
the kernel works fine though when uart4 is disabled in dtb. Its defined as:

&uart4 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_uart4>;
/delete-property/ dmas;
/delete-property/ dmas-names;
fsl,dte-mode;
status = "okay";
};

pinctrl_uart4: uart4grp {
fsl,pins = <
MX8MM_IOMUXC_UART4_RXD_UART4_DCE_RX 0x140
MX8MM_IOMUXC_UART4_TXD_UART4_DCE_TX 0x140
>;
};

Anything I am missing or any advice on this ?

[AldoG]

Hello,

I see that the changes made to ATF looks correct, even I would say that the changes made by @Chavira are mean to latest releases so if used in old releases some tunning may be needed.

I do not see the device tree changes, are those in place?

Best regards,
Aldo.

[charleshuang · Accepted solution]

Hi @AldoG 

We find the solution and can use the UART4 from Linux User Space

Thanks for your help.

[Chirag]

Hello, @charleshuang

Can you provide any information regarding this ? I am having an exact same issue. I have updated imx-atf changes though.

Thank You.