[Bug 59431] [snb efi gmux] imac 12,1 blank screen upon booting

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=59431

--- Comment #37 from William <kc at cobradevil.org> ---
(In reply to comment #36)
> William: Regarding the issue with efifb not working without the patch I
> supplied, it seems the information efifb requires normally either comes from
> the bootloader, or else the kernel can discover the information itself if
> booted using the EFI stub or EFI handover protocol. The failure to work on
> your system without the quirk could be due to either a bug in the EFI
> firmware or a problem with how the kernel is being booted.
> 
> Do you have working graphics in your bootloader? If so the problem is
> probably with how the kernel is booted. Are you using the standard Ubuntu
> boot setup (i.e. grub2), and are you modifying it in any way?

I have no graphics setup or at least not that i am aware off.
I get a ncurses based menu where i can choose the different kernels i have
installed.

Right now i cannot seem to get a console even with or without the
gfxpayload=keep option on the 32bit kernel. When starting the same usb stick on
a macbook air it works with both the 32bit kernel and the 64bit kernel.

We don't use the default ubuntu grub install because we setup a small efiboot
environment  using grub-mkimage.
grub-mkimage -O x86_64-efi -o bootx64.efi  search_fs_uuid fat ext2 normal boot
configfile linux

We then install this onto a small fat partition 8 MB.
I will attach the efiboot with the grub options.

I think the main problem is that we are starting a 32bit kernel from a 64bit
firmware. I had earlier issues with that even on the standard macbook air see
also: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1082059

But this has been addressed.

I think something else is going wrong with setting up efifb with a 32bit kernel
booted from 64 bit firmware and that that is the reason i don't get a console.
>From the dmesg log i see connector 4 is vga-1 on 64bit kernel and vga-2 on the
32bit kernel, not sure if that could mean anything.

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