Using UART2 from Linux on i.MX8M-EVK board

[BernardDAUTREVA]

On the i.MX8M-EVK board there are two UARTs available through the USB micro socket, which is fine.

One is used as a Linux console and the other is connected to the Cortex-M4 core.

In my case I would not use the Cortex-M4 but would like to have access to the UART2 from Linux. I presume I will have to modify the DTS, adding a node for uart2, but I wonder what pin multiplexing definitions to use (probably I will have to add them too).

Moreover, I presume that the UART2 was dedicated to the Cortex-M4 and I don't know how (and especially where) to reprogram the RDC (Resource Domain Controler) to arrange for the UART2 to be accessible from the Cortex-A53). Or is the UART2 declared as a shared peripheral at boot time?

Thanks for any pointer to relevant BSP documentation or to any hints on how to do that.

Bernard

[igorpadykov]

Hi Bernard

RDC is not used at boot time and it has default settings.

To have access to the UART2 from Linux one can use below dts (set status = "okay" for UART2)

linux/arch/arm64/boot/dts/freescale/fsl-imx8mq-evk-root.dts

fsl-imx8mq-evk-root.dts\freescale\dts\boot\arm64\arch - linux-imx - i.MX Linux kernel 

For using UART2 with M4 below dts file is used ( UART2 is dedicated to the Cortex-M4)

linux/arch/arm64/boot/dts/freescale/fsl-imx8mq-evk-m4.dts

fsl-imx8mq-evk-m4.dts\freescale\dts\boot\arm64\arch - linux-imx - i.MX Linux kernel 

Best regards
igor
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