====== Gentoo Installation on AML-S905X-CC (Le Potato) ======

=== Requirements ===

  * 2x microSD cards
  * USB microSD card adapter
  * Le Potato board
  * usb to tty cable so you can see whats going on over UART

=== Steps ===

  - flash raspian image from Libre Computer to both microSD cards [[https://distro.libre.computer/ci/raspbian/11/2022-09-22-raspbian-bullseye-arm64-lite%2Baml-s905x-cc.img.xz|Download]]
  - insert one of the microSD cards you flashed into the Le Potato and boot (follow initial setup as required)
  - insert the second microSD into usb adapter and insert adapter into usb slot on Le Potato, this is where you will make changes and install Gentoo
  - delete root partion (second partition)
  - create a swap partition if desired
  - create a new root partition
  - mkfs.btrfs on the new root partition
  - mount new partition at /mnt/gentoo (mkdir if needed)
  - mount the existing EFI partition  on /mnt/gentoo/boot/efi (mkdir first)
  - cp -rp the firmware, kernel modules, kernel headers and the rest of /boot from the raspian microSD you are booted on to the one on the adapter to the same path
  - use lsmod and put list of modules into /etc/modules-load.d/raspian-modules.conf
  - at this point you can mostly follow the normal gentoo amd64 handbook for setup (use end0 for ethernet device)
  - make sure you adjust /etc/inittab if you want to use the uart interface<code>
# Architecture specific features
f0:12345:respawn:/sbin/agetty 115200 ttyAML0 vt100
</code>
  - when you get to bootloader installation/configuration emerge grub with efi-64 (add following to /etc/portage/make.conf)<code>
GRUB_PLATFORMS="efi-64"
</code>
  - grub-mkconfig -o /boot/grub/grub.cfg
  - grub-mkstandalone -O arm64-efi -o /boot/efi/EFI/BOOT/BOOTAA64.EFI "boot/grub/grub.cfg=/boot/grub/grub.cfg"

=== Custom Kernel ===

  * [[https://github.com/libre-computer-project/libretech-linux.git|Github Source]]
  * Branch: v6.0/libretech-master
  * Start with Config from /boot (from Raspbian image)
  * make menuconfig/make/make install/make modules_install
  * emerge dracut
  * dracut --kver="6.0.19-419654-g73f2949c2dd9"
  * grub-mkconfig -o /boot/grub/grub.cfg
  * grub-mkstandalone -O arm64-efi -o /boot/efi/EFI/BOOT/BOOTAA64.EFI "/boot/grub/grub.cfg=/boot/grub/grub.cfg"


=== Qemu chroot environment (For compiling packages on amd64 host with more memory/cpu)===

  * emerge --ask app-emulation/qemu
  * QEMU_USER_TARGETS="aarch64" QEMU_SOFTMMU_TARGETS="aarch64" USE="static-user static-libs" emerge --ask --buildpkg --oneshot qemu
  * cd /usr
  * mkdir potato
  * cd potato
  * wget https://bouncer.gentoo.org/fetch/root/all/releases/arm64/autobuilds/20230416T233158Z/stage3-arm64-openrc-20230416T233158Z.tar.xz
  * tar xvf stage3*tar.xz
  * cp -rp kernel firmware headers modules to the new chroot env
  * <code>ROOT=$PWD/ emerge --ask --usepkgonly --oneshot --nodeps qemu</code>
  * make file requires -pid-sandbox in features or qemu bug rears its ugly head
  * mkdir any mount points that dont' exist for the chroot script
  * setup your package.use etc

/etc/portage/package.make
<code>
# These settings were set by the catalyst build script that automatically
# built this stage.
# Please consult /usr/share/portage/config/make.conf.example for a more
# detailed example.
COMMON_FLAGS="-O2 -pipe -march=armv8-a+crypto+crc -mabi=lp64 -mtune=cortex-a53"
CFLAGS="${COMMON_FLAGS}"
CXXFLAGS="${COMMON_FLAGS}"
FCFLAGS="${COMMON_FLAGS}"
FFLAGS="${COMMON_FLAGS}"
# WARNING: Changing your CHOST is not something that should be done lightly.
# Please consult https://wiki.gentoo.org/wiki/Changing_the_CHOST_variable before changing.
CHOST="aarch64-unknown-linux-gnu"
MAKEOPTS="-j4"
FEATURES="-pid-sandbox buildpkg"
#FEATURES="-collision-protect sandbox buildpkg noman noinfo nodoc"
PKGDIR=/var/potato/binpkgs/
# NOTE: This stage was built with the bindist Use flag enabled

# This sets the language of build output to English.
# Please keep this setting intact when reporting bugs.
LC_MESSAGES=C
USE="-X gpm fbcon alsa -udev"
ACCEPT_LICENSE="-* @FREE @BINARY-REDISTRIBUTABLE"
GRUB_PLATFORMS="efi-64"
PORTDIR_OVERLAY="/var/db/repos/portage_overlay"
</code>

potato-chroot.sh
<code>
/etc/init.d/qemu-binfmt start

cd /usr/potato
mount -t proc none proc
mount -o bind /dev dev
mount -o bind /var/db/repos/gentoo var/db/repos/gentoo
mount -o bind /sys sys
cp /etc/resolv.conf etc/resolv.conf
echo ':aarch64:M::\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7:\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-aarch64:' > /proc/sys/fs/binfmt_misc/register

chroot . /bin/bash --login

umount sys
umount var/db/repos/gentoo
umount dev
umount proc
</code>

=== Configuring binary package repo over ssh ===

  * get public key from root user on potato
  * add potato root public key to authorized_keys file of a user with read access on the compile host
  * add feature and pkg host to /etc/portage/make.conf

<code>
PORTAGE_BINHOST="ssh://user@pkghost/usr/potato/var/potato/binpkgs"
FEATURES="getbinpkg"
</code>

=== Adding RTC ===

  * wire your RTC to the GPIO same as a raspberry pi{{:rtc.jpeg?400|}}
  * install deps<code>emerge --ask dtc libgpiod</code>
  * clone libretech-wiring-tool<code>
git clone https://github.com/libre-computer-project/libretech-wiring-tool.git
</code>
  * compile and install the overlays and commands<code>
make
make install
</code>
  * create an init script to add the overlays: 
      * <code> vim /etc/init.d/rtc</code>
      * <code>
#!/sbin/openrc-run
# Copyright 2023 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2

name="i2c rtc overlays"
description="make rtc "

depend() {
    before hwclock
}

start() {
    /opt/librecomputer/libretech-wiring-tool/ldto enable i2c-ao
    /opt/librecomputer/libretech-wiring-tool/ldto enable i2c-ao-ds3231
}
</code>
  * set make script executable and add too boot runlevel<code>
chmod 755 rtc
rc-update add rtc boot
</code>
  * reboot and check dmesg, if it worked you'll see a log like so<code>
[   11.809520] rtc-ds1307 1-0068: registered as rtc0
[   11.810886] rtc-ds1307 1-0068: setting system clock to 2023-05-04T11:58:05 UTC (1683201485)
</code>
  * you can also check with i2cdetect denoting the UU in 0x68 location<code>
mobilemouse ~ # i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- 57 -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
</code>

=== GPIO Reference ===

{{:potatogpio.png?800|}}