Add documentation for arm/aarch64

[flexibeast]

Cf. @Johnnynator's comment on /r/voidlinux here.

[ericonr]

From IRC, agrisis was having trouble with the udevd service not working, as well as issues in dhcpcd and others. I believe they removed that line to get it to work.

      agrisis │ omg I figured it out
      agrisis │ kernel command line: console=/dev/ttyS0
      agrisis │ that messes up runit I guess
      agrisis │ https://old.reddit.com/r/voidlinux/comments/dwcste/aarch64_on_rock64_hanging_on_boot/

[Fluffkin]

Couple of ideas for things to add:

The current default /boot/cmdline.txt setting for elevator is "noop". Changing that to "deadline" may improve apparent performance.

In /boot/config.txt if you set gpu_mem to anything less than 32 (MB), you will get alarming looking VCHI related errors in your boot log. They are apparently harmless, but do mean you are using a cut down version of the firmware.

If you've plugged in an LCD monitor to your HDMI on the Pi, you may get weird overscan / resolution options. You'll need to set hdmi_group to 2 in /boot/config.sys and lookup the correct values for hdmi_mode / your monitor here from the DMT group: https://www.raspberrypi.org/documentation/configuration/config-txt/video.md

Installing the package "fake-hwclock" is very useful for maintaining a roughly correct system time between reboots.

[amak79]

Another idea for RPi.

The default CPU governor for the RPi kernel is powersave. This can make the system sluggish under certain loads as it will force the lowest frequency. A better default is ondemand which can be set for all cores with:

echo ondemand > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor

I put the above in /etc/rc.local

[flexibeast]

@ericonr: Is there anything from this discussion that still needs to be added to the "ARM Devices" section?

[ericonr]

Most of it, I think. But I don't know how many of them are Void specific, and I don't know exactly how they all work.

I'd also like to leave this issue open to track the addition of the other ARM boards.