i.MX8M-Plus U-Boot RDC settings

[vix]

In the "i.MX 8M Plus Applications Processor Reference Manual, Rev. 1, 06/2021" I read the chapter "3.2 Resource Domain Controller (RDC)" and I see the reset value for the several RDC_PDAPxxx registers.

On my evaluation board, if I halt the boot inside U-Boot, I see that 3 RDC_PDAPxxx registers have values different from the reset/default value:

• RDC_PDAP8 which is SAI3 has a value of 0x00000003
• RDC_PDAP29 which is RDC has a value of 0x0000000B
• RDC_PDAP105 which is UART2 has a value of 0x00000003

Can someone explain where in the U-Boot sources (https://github.com/nxp-imx/uboot-imx) I can see the section responsible for these settings.

And, moreover, why they're necessary.

In my usage scenario I would like using UART2 from Cortex-M (domain 1), but it doesn't seem possible without patching the default U-Boot from NXP.

But I prefer not to going on with these, because I see it as a difficult job, with possible heavy consequences in case of mistakes.

[Sanket_Parekh · Accepted solution]

Hi @vix ,

I hope you are doing well.

RDC PDAP registers are configured in ATF.

Please refer to imx_rdc_cfg in  imx-atf/plat/imx/imx8m/imx8mp/imx8mp_bl31_setup.c 

One can add the below line in imx_rdc_cfg in imx8mp_bl31_setup.c to use UART2 in the m7 core.

RDC_PDAPn(RDC_PDAP_UART2, D1R | D1W),

Please make sure to add the below node in the dts file.

uart2{

         status = "disabled";

}

Please make a note that uart2 is used for debug console in default BSP.

One needs to make changes to use another uart as A53 debug console.

Thanks & Regards,

Sanket Parekh