Flicker Free Boot

Flicker free boot is a Linux feature that seeks to eliminate display flickers that occur during system boot. It was created by Hans de Goede and is available in Fedora since version 30 and can be implemented in on Gentoo systems.

Warning
This is not an easy task to accomplish and might break the system. It is recommended to make a backup of all files in the /boot partition before attempting this tutorial. No support for boot failures will be provided by Gentoo (forums, bugs, email, IRC) when using software outside of the repository. Follow this tutorial at your own risk!

Testing

Community members are encouraged to share success or failure results in the following table. This way we can get a more accurate view of which systems obtain success.

Device Model	CPU (Code Name)	Notes
Dell Inspiron 15 5567	Intel Core i7-7500U (Kaby Lake)	The boot process is completely fluent, using kernel patches from [1] or kernel version below 5.7.
Dell PowerEdge T20	Intel Xeon E3-1225v3 (Haswell)	The boot process is around 80% fluent. It flickers once for 2 - 3 sec. Unfortunately it's the same when booting from a Microsoft Windows 10 based USB key, so it appears to be the way it was implemented.
Lenovo ThinkPad P52	Intel Core i7-8750H (Coffee Lake)	The boot process is completely fluent
Lenovo Thinkbook 14s Yoga	11th Gen Intel(R) Core(TM) i5-1135G7 (Tiger-Lake)	Works great with the systemd-boot option; tested with =sys-kernel/gentoo-kernel-bin-5.12.8.

Requirements

Hardware / Software

A working UEFI setup, preferably with a Intel Skylake (6th Generation) or more recent Intel processor.
Older (3rd to 5th Generation Core iXXXX series processors may work, but are not guaranteed. Test to find out.
The Intel integrated (i915) series graphics adapters must be used. Other graphics cards (AMD, NVIDIA, etc.) are not (yet) supported by flicker free boot.
The specified system must boot up in native UEFI mode. CSM mode needs to be disabled.
The specified system must use a manually compiled kernel. Testing with a genkernel created kernel has not been completed.
When using older Ivy Bridge / Haswell / Broadwell based systems, it is recommended to use least sys-kernel/gentoo-sources version 4.20.17 or higher due to a bug that actually causes the screen to go to stand-by mode and turn back on.
Kernel version 5.7.0 or higher does not honor the i915.fastboot kernel parameter [2]. Use the patches located on that bug report or use a version below 5.7.0.
This guide assumes the kernel has been configured correctly with the appropriate options for framebuffer support and such.
This guide assumes /dev/sda1 has been configured as the ESP (/boot/efi) partition. If it is not, then adjust the commands for the paths accordingly.

Knowledge

A working Gentoo setup, preferably configured with EFI stub.
Intermediate to advanced knowledge about the Linux boot process.

Summary

This tutorial assumes a working Gentoo setup is in place. This setup boots in (U)EFI mode using GRUB with CSM mode disabled and is using an Intel processor with it's own integrated graphics card.

Installing the required software

In order to be able to successfully get everything working, the following software configuration will be needed.

Setting the correct USE flags for plymouth

In order to set the correct use flags for plymouth, you'll need to take the following steps:

Run the command:

root #nano -w /etc/portage/package.use/plymouth

Add the following line to the file:

FILE /etc/portage/package.use/plymouth

sys-boot/plymouth libkms pango

1. NOTE: libkms is the minimal requirement for the splash screen to show up. pango is required for interactivity (e.g.: This is necessary to have the ability to enter a LUKS password on a nice graphical screen). The gtk and gdm USE flags should be added respectively when using GDM as the Display manager or LightDM with GTK.
2. NOTE: Do NOT enable the static-libs USE flag. This USE flags will plymouth and may causes the package not to compile or display themes.
Press CTRL+o, and press Enter and press CTRL+x in order to save the file.
Now install sys-boot/plymouth:

root #emerge --ask --verbose sys-boot/plymouth

1. Be sure to verify that the correct USE flags have been set.

Using dracut

This has been tested to work by using the amd64 version of dracut. Using the latest available version of dracut from Portage is recommended.

Install the package:

root #emerge --ask sys-kernel/dracut

Then create the initramfs image via:

root #dractut --hostonly

More information is available on the Dracut page.

Setting up EFI stub

Usage of EFI stub can be found at EFI stub and Efibootmgr. Make the i915.fastboot=1 kernel parameter is included, and include the path to the initranmfs generated by dracut, like so:

root #

efibootmgr -c -d /dev/sda -p 1 -L "Gentoo" -l '\vmlinuz-5.4.97-gentoo' -u '... i915.fastboot=1 initrd=\initramfs-5.4.97-gentoo.img ...'

Finally, reboot and hope it works.

Alternative: setting up systemd-boot (systemd users only)

Alternatively systemd-boot can be configured for a flicker free boot. This seems to be an attractive option for users, who want to use a bootloader some configuration options (e.g. for dual-booting with Windows or another operating system).

Follow the steps from the systemd/systemd-boot article to set up systemd-boot.

Next, configure the bootloader entry to look something like the following:

FILE /boot/efi/loader/entries/gentoo.confDefault settings

title Gentoo Linux
linux /EFI/Linux/vmlinuz
initrd /EFI/Linux/initrd.img
options [...] i915.fastboot=1 quiet splash

External References