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ConiKost
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PostPosted: Sun Feb 07, 2016 6:38 pm    Post subject: No video out on UEFI boot Reply with quote

Hi!
I am currently trying to install gentoo on a UEFI PC (Core i7-6700k, Gigabyte Z170X, NVidia GTX 980Ti, 32GB RAM, mSATA SSD).
But I am totally unable to boot my kernel. Something does not work, because I am getting no video output from my video card.

I've build an UEFI-stub kernel, which is beeing loaded by my UEFI. But after selecting the UEFI entry and booting it, I am not getting any new video output. I am still seeing my UEFI boot screen.

The SSD is encrypted using LUKS. So I am using my own written initrd and kernel (no dracut/genkernel). But I am pretty sure, my kernel is booting.
Because, when I do remove my initrd, I can clearly see, after selecting my UEFI boot entry, 2-3 seconds later, my keyboard LEDs are flashing and 15 seconds later, the PC is rebooting (That's the timeout, which I set in my kernel, to reboot on kernel panic!).
This makes sense, as my initrd is missing and the kernel cannot mount the root device. But I dont have any output on my monitor..

So I guess, with enabled initrd, the systems also boots and is waiting, that I do enter my password.
What could I missing? I don't have a clue, that could be missing, that I have no video output at all. Setting "nomodeset" or compiling a kernel without CONFIG_FB (forcing to VGA text console) does also not help.

Kernelconfig: https://www.bl4ckb0x.de/files/config-4.4.1-gentoo

When I do boot GRUB instead my kernel, I am getting a GRUB output on my monitor. But after boot my kernel now, I see GRUB forever and have the same behaviour, as with my stub kernel, but seeing my grub.
Any ideas?
Thanks!
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chithanh
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PostPosted: Sun Feb 07, 2016 9:09 pm    Post subject: Reply with quote

Maybe nouveau does not support that card properly yet?

Try building nouveau as module and also enabling CONFIG_FB_SIMPLE.
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ConiKost
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PostPosted: Sun Feb 07, 2016 10:23 pm    Post subject: Reply with quote

chithanh wrote:
Maybe nouveau does not support that card properly yet?

Try building nouveau as module and also enabling CONFIG_FB_SIMPLE.


Hi!
Enabling CONFIG_FB_SIMPLE did work. It does not matter, if nouveau is compiled in or disabled entirely. With that, I am getting video output and can use gentoo. If seems, I was right and the kernel was booting itself fine and waiting for me, to enter a password ;) I will also give a try with nouveau to see the exact error messages.

Is framebuffer a must in UEFI? So, what's the purpose of CONFIG_FB_EFI? I've had this enabled. Shouldn't that provide a framebuffer for me?
I've also seen, that my older "SystemRescueCd" (Kernel 3.19 or 4.0-4.1, not exactly sure) is booting with efifb in dmesg.

If I disable entirely framebuffer (CONFIG_FB), shouldn't I get at least classic vga 80x25 text mode output, because this isn't working for me. That's pretty strange. Or does this work only with CMS / BIOS?

Thanks!
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chithanh
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PostPosted: Sun Feb 07, 2016 11:07 pm    Post subject: Reply with quote

UEFI will usually initialize the card in graphics mode and not in VGA text mode. I'm not even sure whether going to VGA text mode is possible unless you boot in BIOS mode..

The simplefb driver will detect that the graphics have been initialized (by UEFI, GRUB, etc.) and continue to use that framebuffer.
The efifb driver will try to re-initialize the graphics through UEFI GOP.
nouveau will detect and replace either simplefb or efifb and perform an initialization on its own.

In your case it could be that either efifb failed for some reason, or that handover to nouveau didn't work, or nouveau could not initialize the card. dmesg after trying to load the nouveau module might tell more.
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