2407301_en-US

[#1]

Dynamic ARM frequency switching work in U-Boot for i.MX8MP

I'm using i.MX8MP custom board with a part that supports 1.6GHz and 1.8GHz speed grades. By default, U-Boot boots the ARM core at 1200MHz regardless of the chip's actual speed grade.

Questions:

1. How does U-Boot detect and apply the correct ARM frequency based on the SoC's fused speed grade? Is there dynamic switching at the U-Boot stage, or is this left entirely to Linux?
2. What's the correct or recommended way to make U-Boot, boot at 1.6GHz or 1.8GHz instead of the default 1200MHz?
3. Do I also need to adjust VDD_ARM voltage in PMIC when changing the frequency, and if so, how should that be sequenced?

Any guidance or reference examples would be appreciated. Thanks.

Re: Dynamic ARM frequency switching work in U-Boot for i.MX8MP

Hi @Nvcee,
Thank you for contacting NXP Support!

1) All voltage and frequency initializations are performed in the soc.c file within U-Boot:

https://github.com/nxp-imx/uboot-imx/blob/lf_v2026.04/arch/arm/mach-imx/imx8m/soc.c

2) The dynamic voltage and frequency scaling driver operates only under Linux.

3)You can hardcode the clock and voltage initializations in soc.c. However, you must ensure that the selected part number is correct, as using settings intended for a different device variant could cause the system to hang or behave unexpectedly.

Best regards,
Chavira