Kernel with working cpufreq

#1

Hi, I’m planning to use Radxa ZERO 3E in my project. For validation I’ve installed Gentoo on it with the mainline kernel (tried 6.14.6 and 6.15.0-rc5) and U-Boot (v2025.04). Everything that I need is working: Ethernet, SD card, I2C, USB, hwmon, and performance is more than enough. Unfortunately, cpufreq doesn’t seem to work, and I can’t test max power draw and max temperature/throttling under maximum load.
I’ve also built a kernel using BSP (./bsp linux rk356x) and extracted files from it (linux-image-5.10.160-1-rk356x_5.10.160-1_arm64.deb) into the right places, plus copied the device tree (rk3566-radxa-zero3.dtb). But when I try to boot it, there is nothing on the serial console, and the green LED is constantly on, which I think means it froze.
Where can I find a kernel with a working cpufreq, or what am I doing wrong with the BSP kernel?

U-Boot command to run the BSP kernel:
env set bootargs root=/dev/mmcblk0p4 ipv6.disable=1 rw console=ttyS2,115200; load mmc 1:3 $fdt_addr_r rk3566-radxa-zero-3e-5.10.160.dtb ; load mmc 1:3 $kernel_addr_r vmlinuz-5.10.160-1-rk356x; booti $kernel_addr_r - $fdt_addr_r

EDIT:
I’ve made some digging in device tree, and I changed baud to 115200. It booted, but I’m getting rcu stalls. Unfortunately, I don’t have any converter that works with 1.5M baud rate.
[ 71.361654] rcu: 1-…: (18000 ticks this GP) idle=6fe/1/0x4000000000000002 softirq=18/18 fqs=5995
[ 251.095198] rcu: INFO: rcu_sched self-detected stall on CPU
[ 251.095256] rcu: 1-…: (70422 ticks this GP) idle=6fe/1/0x4000000000000002 softirq=18/18 fqs=23857
[ 429.858471] rcu: INFO: rcu_sched self-detected stall on CPU
[ 429.858528] rcu: 1-…: (121039 ticks this GP) idle=6fe/1/0x4000000000000002 softirq=18/18 fqs=41515

#2

I bought a new UART adapter and did some tests with building kernel on radxa-zero3_bookworm_kde_t2.output.img, results:
Current draw is about 0.7A, but for a moment it was about 0.9A during boot.
CPU temperature under load is about 83*C, and frequency is switching between 1.4 and 1.6GHz.

#3

how did you install gentoo on it? And you were able to get the overlays working on gentoo?

#4

Sorry for the late reply; this install was just a test to check if this board will be good for Docker Swarm. I was busy testing the Radxa Rock 5 ITX as a Docker manager and accidentally damaged it, and I’m slowly trying to repair it.

I prepared partitions on the SD card according to: https://opensource.rock-chips.com/wiki_Partitions, then unpacked stage3 into it and systemd-nspawn into it (using qemu_user_target). Then I build u-boot and kernel and put them into the right places.

I don’t have enough knowledge to mess with overlays – I just decompiled the working device tree, edited it and compiled it back.