Announcing flickerfree boot for Fedora 29

[hansdegoede]

A big project I've been working on recently for Fedora Workstation is what we call flickerfree boot. The idea here is that the firmware lights up the display in its native mode and no further modesets are done after that. Likewise there are also no unnecessary jarring graphical transitions.

Basically the machine boots up in UEFI mode, shows its vendor logo and then the screen keeps showing the vendor logo all the way to a smooth fade into the gdm screen. Here is a video of my main workstation booting this way.

Part of this effort is the hidden grub menu change for Fedora 29. I'm happy to announce that most of the other flickerfree changes have also landed for Fedora 29:

1. There have been changes to shim and grub to not mess with the EFI framebuffer, leaving the vendor logo intact, when they don't have anything to display (so when grub is hidden)


2. There have been changes to the kernel to properly inherit the EFI framebuffer when using Intel integrated graphics, and to delay switching the display to the framebuffer-console until the first kernel message is printed. Together with changes to make "quiet" really quiet (except for oopses/panics) this means that the kernel now also leaves the EFI framebuffer with the logo intact if quiet is used.


3. There have been changes to plymouth to allow pressing ESC as soon as plymouth loads to get detailed boot messages.

With all these changes in place it is possible to get a fully flickerfree boot today, as the video of my workstation shows. This video is made with a stock Fedora 29 with 2 small kernel commandline tweaks:

1. Add "i915.fastboot=1" to the kernel commandline, this removes the first and last modeset during the boot when using the i915 driver.


2. Add "plymouth.splash-delay=20" to the kernel commandline. Normally plymouth waits 5 seconds before showing the charging Fedora logo so that on systems which boot in less then 5 seconds the system simply immediately transitions to gdm. On systems which take slightly longer to boot this makes the charging Fedora logo show up, which IMHO makes the boot less fluid. This option increases the time plymouth waits with showing the splash to 20 seconds.

So if you have a machine with Intel integrated graphics and booting in UEFI mode, you can give flickerfree boot support a spin with Fedora 29 by just adding these 2 commandline options. Note this requires the new grub hidden menu feature to be enabled, see the FAQ on this.

The need for these 2 commandline options shows that the work on this is not yet entirely complete, here is my current TODO list for finishing this feature:

1. Work with the upstream i915 driver devs to make i915.fastboot the default. If you try i915.fastboot=1 and it causes problems for you please let me know.


2. Write a new plymouth theme based on the spinner theme which used the vendor logo as background and draws the spinner beneath it. Since this keeps the logo and black background as is and just draws the spinner on top this avoids the current visually jarring transition from logo screen to plymouth, allowing us to set plymouth.splash-delay to 0. This also has the advantage that the spinner will provide visual feedback that something is actually happening as soon as plymouth loads.


3. Look into making this work with AMD and NVIDIA graphics.

Please give the new flickerfree support a spin and let me know if you have any issues with it.