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Modern kernel GPU driver knows enough about the GPU to switch video modes (and usually also enough to detect connected monitors) and setup some kind of linear f

by dfox 9y ago

Modern kernel GPU driver knows enough about the GPU to switch video modes (and usually also enough to detect connected monitors) and setup some kind of linear framebuffer mode. The first font used for FB-emulated console is statically linked into relevant module and usually gets replaced with more complete font by initramfs code. IIRC on my desktop the switch to graphical mode happens about 300ms after loading the kernel. Funnily enough grub2 before that also runs in 4k graphics mode, which given the 8x16px font is somewhat absurd (and the screen redraw is slow enough that you can see that it for some reason happens from bottom to top) Edit: this is with amdgpu, but both intel, nouveau and ATI rage XL on server motherboards (which is somehow suboptimal :)) behave similarly on debian. Maybe with nvidia driver you still get native text mode on consoles (for a long time nvidia driver was known to interfere with operation of linux framebuffer infrastructure, but I don't known how this works today).

shmerl 9y ago
> IIRC on my desktop the switch to graphical mode happens about 300ms after loading the kernel. Funnily enough grub2 before that also runs in 4k graphics mode, which given the 8x16px font is somewhat absurd (and the screen redraw is slow enough that you can see that it for some reason happens from bottom to top) Yeah, I noticed that. GRUB font looks similar to the one that's rendered after the kernel GPU driver takes over. I also noticed during boot (when systemd messages are showing up) a transition with amdgpu (RX 480, Polaris) where it displays a color mess for a split moment, and redraws the screen in new font after that. Never saw that with Intel. I haven't used Nvidia in a while, but their blob doesn't support proper framebuffer if I remember correctly, so it causes an ugly resolution during boot.
- dfox 9y ago
  On Bonaire (no idea what the card is as I bought it on the basis of being supported by amdgpu and having right combination of outputs and nothing else) I don't get mess for split second, but after the switch to graphical mode first two lines are partialy replaced by randomly colored special characters.
  - shmerl 9y ago
    That mess started appearing at some point with kernel 4.14.x. It's also isolated to upper area and doesn't take the whole screen, but it's more than two lines.
    - jlgaddis 9y ago
      I've seen this as well and noticed that it was only after moving to 4.14.
jlgaddis 9y ago
This happens on my desktop/workstation as well (w/ NVIDIA cards) but only when using UEFI. It doesn't occur when using legacy/BIOS mode. I've got two ThinkPads sitting here as well and it doesn't happen on them. One has Optimus (Intel+NVIDIA), the other just has built-in Intel graphics; both are using legacy/BIOS mode. I haven't tested it using UEFI.

by dfox 9y ago

shmerl 9y ago

> IIRC on my desktop the switch to graphical mode happens about 300ms after loading the kernel. Funnily enough grub2 before that also runs in 4k graphics mode, which given the 8x16px font is somewhat absurd (and the screen redraw is slow enough that you can see that it for some reason happens from bottom to top) Yeah, I noticed that. GRUB font looks similar to the one that's rendered after the kernel GPU driver takes over. I also noticed during boot (when systemd messages are showing up) a transition with amdgpu (RX 480, Polaris) where it displays a color mess for a split moment, and redraws the screen in new font after that. Never saw that with Intel. I haven't used Nvidia in a while, but their blob doesn't support proper framebuffer if I remember correctly, so it causes an ugly resolution during boot.

dfox 9y ago
On Bonaire (no idea what the card is as I bought it on the basis of being supported by amdgpu and having right combination of outputs and nothing else) I don't get mess for split second, but after the switch to graphical mode first two lines are partialy replaced by randomly colored special characters.
- shmerl 9y ago
  That mess started appearing at some point with kernel 4.14.x. It's also isolated to upper area and doesn't take the whole screen, but it's more than two lines.
  - jlgaddis 9y ago
    I've seen this as well and noticed that it was only after moving to 4.14.

jlgaddis 9y ago

This happens on my desktop/workstation as well (w/ NVIDIA cards) but only when using UEFI. It doesn't occur when using legacy/BIOS mode. I've got two ThinkPads sitting here as well and it doesn't happen on them. One has Optimus (Intel+NVIDIA), the other just has built-in Intel graphics; both are using legacy/BIOS mode. I haven't tested it using UEFI.