i.MX8MQ changing ENET_REF_CLK_ROOT source from 25M_REF_CLK to PLL and enabling spread spectrum mode

[harshitshah]

Hi,

We are facing some EMI-related issues on our board. We wanted to change the following to check the reduction in EMI.

1) Change the ENET_REF_CLK_ROOT source from 25M_REF_CLK to PLL1 (We found by reading the CCM_TARGET_ROOT83)

2) Enable the spread spectrum mode and set it to center and 0.25.

Please provide us with how to modify the same in the Linux kernel.

Regards.

[harshitshah]

Thanks Igor. I will check with those links.

Can you comment on how to enable spread spectrum mode in linux kernel as well? 

Regards.

[igorpadykov]

Hi Harshit

for changing clock source in device tree one can look at below examples

https://community.nxp.com/t5/i-MX-Processors/Where-pll4-bypass-src-is-set-to-choose-osc-24MHz-or-CLK...

https://community.nxp.com/t5/i-MX-Processors/i-MX7D-24MHz-clock-output-to-CCM-CLK1-P-pin/m-p/650813

Unfortunately I am not aware of spread spectrum mode examples, so may be recommended to proceed with

help of  https://contact.nxp.com/new-prof-svcs-sw-tech  for developing them.

Best regards
igor