kernel build 5.10.52 issue?

[liuyongzhiatyahoo]

Hi, Kevin,

I am cross-compiling from Ubuntu 20.04 (X86_64) for RPI4, using the compiler at "~/rpi-kernel/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-"

$ make bcm2711_defconfig # PASS
$ make menuconfig # PASS, linux/arm 5.10.52 kernel configuration, preemptible kernel (RT), High Resolution Timer, CONFIG_HZ 1000Hz, CPU performance governor.

skylake@skylake:~/Documents/rpi-kernel/linux$ make -j4 zImage
SYNC include/config/auto.conf.cmd
CC scripts/mod/empty.o
CC scripts/mod/devicetable-offsets.s
cc1: error: -Werror=date-time: no option -Wdate-time
cc1: error: -Werror=date-time: no option -Wdate-time
make[1]: *** [scripts/Makefile.build:280: scripts/mod/empty.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: *** [scripts/Makefile.build:117: scripts/mod/devicetable-offsets.s] Error 1
make: *** [Makefile:1213: prepare0] Error 2

Do you have any tips, thanks a lot.

Regards,
Yongzhi

[liuyongzhiatyahoo]

Have checked minimum requirement to compile the kernel, I found the following tools missing at 20.04.pcmiautils, grub, mcelog, libcrypto, quota-tools, PPP, nfs-utils. Do they matter? thanks.

[kdoren]

@liuyongzhiatyahoo ​I build 64-bit kernel on 32-bit RPi, which also requires CROSS_COMPILE, so should be similar to building on Ubuntu x86_64. I can't speak to your specific problem, but for 64-bit kernel build, here are a few thoughts:

1, to build 64-bit RT 5.10 arm64 kernel, you need to disable KVM, and make Image (not zImage)
2. This tutorial on cross-compiling 64-bit kernel is helpful and should apply to Ubuntu x86_64 also: https://www.tal.org/tutorials/raspberry-pi3-build-64-bit-kernel
3. I believe dependencies for kernel building are minimal (see above tutorial link). My notes also show "sudo apt-get install flex bison libncurses-dev libssl-dev"

Here is how I build 64-bit kernel:

export ARCH=arm64
export KERNEL=kernel8
export CROSS_COMPILE=/opt/aarch64/bin/aarch64-linux-gnu-
make clean
make bcm2711_defconfig
make menuconfig
# disable KVM
# enable PREEMPT_RT
# cpufreq governor - performance
# Timer Freq - 1000 Hz
make -j4 Image modules dtbs

I sometimes run 64-bit PREEMPT_RT kernel on 32-bit system. I'm still uncertain whether this makes performance better or worse than 32-bit kernel. Cyclictest suggests better, but real-world testing suggests worse.

[kdoren]

@liuyongzhiatyahoo FYI I posted a release of r5.10.59-rt51 that include 64-bit deb packages. Also I posted some build info in a response to an issue raised here: #14