Merge ~vanvugt/ubuntu/+source/initramfs-tools:smaller-earlier-framebuffer into ~ubuntu-core-dev/ubuntu/+source/initramfs-tools:ubuntu/devel

[Daniel van Vugt]

Make framebuffer dependencies much smaller in preparation for enabling FRAMEBUFFER=y (LP: #1970069, LP: #1869655).

[Daniel van Vugt (vanvugt)]

Should FRAMEBUFFER=y be moved to plymouth? As in /etc/initramfs-tools/conf.d/plymouth.conf ?

[Benjamin Drung (bdrung)]

FRAMEBUFFER=y makes more sense in plymouth (similar to /usr/share/initramfs-tools/conf-hooks.d/cryptsetup from cryptsetup-initramfs).

[Benjamin Drung (bdrung)]

I wanted to test this change in a QEMU instance (virtio video), but the boot screen degraded to text only. Which bits are needed (kernel, plymouth, etc) to make it work?

[Daniel van Vugt (vanvugt)]

Assuming you're describing a small number of kernel error-level messages then adding loglevel=3 (after quiet) to the command line should suffice. That change is coming in noble proposed kernel 6.8.0-19.19 and is what I've been testing with. Although I haven't tried QEMU, only real machines so far.

[Daniel van Vugt (vanvugt)]

Dropped the FRAMEBUFFER=y, it will be reintroduced later in plymouth. But please do test with FRAMEBUFFER=y.

[Daniel van Vugt (vanvugt)]

Actually it looks like virtio-gpu got dropped by this change. I could reintroduce it but surely one of the other simpler drivers should work in QEMU (with quiet loglevel=3)?

[Benjamin Drung (bdrung)]

I tested with linux 6.8.0-19.19 with following modifications:
1) loglevel=3 added to /etc/default/grub
2) "copy_modules_dir kernel/drivers/gpu/drm $MODULES_EXCLUDE" removed from /usr/share/initramfs-tools/hooks/plymouth
3) FRAMEBUFFER=y set in /etc/initramfs-tools/initramfs.conf

```
$ lsinitramfs /boot/initrd.img-6.8.0-19-generic | grep 'gpu.*ko'
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/drm_dma_helper.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/drm_mipi_dbi.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/drm_ttm_helper.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/drm_vram_helper.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/bochs.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/cirrus.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/gm12u320.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/hx8357d.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/ili9163.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/ili9225.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/ili9341.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/ili9486.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/mi0283qt.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/panel-mipi-dbi.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/repaper.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/st7586.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/tiny/st7735r.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/ttm/ttm.ko.zst
usr/lib/modules/6.8.0-19-generic/kernel/drivers/gpu/drm/vboxvideo/vboxvideo.ko.zst
```

The result in QEMU with virtio-gpu is inconsistent and confusing. The sreen is black for 2-3 seconds before plymouth appears. In most cases I only see plymouth in text mode. If I add the virtio-gpu kernel module, I see the plymouth graphical mode. On reboot sometimes the screen gets no graphic (turned off) for several seconds.

[Daniel van Vugt (vanvugt)]

> The sreen is black for 2-3 seconds before plymouth appears.

That's a separate plymouth bug I'll work on later. I see the same on i915. You might be able to work around it by adding 'plymouth.use-simpledrm' to the command line.

> If I add the virtio-gpu kernel module, I see the plymouth graphical mode.

If virtio support is a priority then I will add virtio-gpu to the list of modules.

> On reboot sometimes the screen gets no graphic (turned off) for several seconds.

Sounds like one or two Plymouth "features":

 * Plymouth won't display anything if it thinks the animation will be short lived.
 * Plymouth displays a black screen while waiting for a "better" DRM driver to be loaded.

I will look at those later.

[Daniel van Vugt (vanvugt)]

Keep in mind flicker-free boot is a long term project with many fixes required. Do not expect everything to just work immediately.

https://bugs.launchpad.net/ubuntu/+bugs?field.tag=flickerfreeboot

[Daniel van Vugt (vanvugt)]

I've added 'virtio-gpu' so hope we're getting close to done here.

The fact that the results are "inconsistent and confusing" is a product of Plymouth's design and that the above list of bugs still needs more work. Don't expect everything to be fixed at once.

The benchmark for flicker-free boot right now is Fedora, which last I checked also booted in text mode in a VM. Our benchmark for this merge request, I think, is that nothing looks worse than it did with the old manual_add_modules line.

[Benjamin Drung (bdrung)]

One last question before merging: The current initramfs in QEMU is working without any DRM drivers and therefore is smaller than with these framebuffer drivers. Why is Plymouth working without DRM drivers?

[Daniel van Vugt (vanvugt)]

Plymouth supports both fbdev and DRM. But it prefers (non-simple) DRM and will wait 8 seconds for DRM to start up before settling for fbdev or SimpleDRM.

[Daniel van Vugt (vanvugt)]

And yes this change does increase the initrd size on some machines at first, but after FRAMEBUFFER=y is introduced in plymouth it keeps the initrd size much lower than it would otherwise be.

[Benjamin Drung (bdrung)]

Thanks. Merged. I'll release this change to noble once 0.142ubuntu22 migrated.

review: Approve

diff --git a/hooks/framebuffer b/hooks/framebuffer
index 7820fd6..c559efd 100755
--- a/hooks/framebuffer
+++ b/hooks/framebuffer
@@ -19,8 +19,8 @@ esac
 
 . /usr/share/initramfs-tools/hook-functions
 
-manual_add_modules "=drivers/char/agp" "=drivers/gpu" "=ubuntu/i915" \
-	fbcon vesafb vga16fb vboxvideo
+manual_add_modules "=drivers/gpu/drm/tiny" \
+	fbcon vesafb vga16fb vboxvideo simplefb efifb virtio-gpu
 
 # if there is a privacy screen then its driver must be loaded before the
 # kms driver will bind, otherwise its probe() will return -EPROBE_DEFER