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Re: Bug#588208: grub-efi-ia32: breaks video of Mac Mini Core 2 Duo

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: Bug#588208: grub-efi-ia32: breaks video of Mac Mini Core 2 Duo
Date: Tue, 06 Jul 2010 22:52:25 +0200
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100620 Icedove/3.0.5

On 07/06/2010 10:54 AM, Colin Watson wrote:
> On Tue, Jul 06, 2010 at 08:37:51AM +0200, Tino Keitel wrote:
>> Package: grub-efi-ia32
>> Version: 1.98+20100705-1
>> Severity: critical
>> Justification: breaks unrelated software
> For what it's worth, I'm likely to downgrade this for a while, until a
> current version gets into testing; the version in testing has some
> serious problems on all architectures right now that badly need to be
> fixed.
>> after installing and using the current grub-efi-ia32, I got a grub menu
>> once, which filled the whole screen in the native display resolution
>> (1680x1050), instead of the 640x480 screen I used to get with older grub
>> versions. Then I booted Linux.
>> After a reboot, I don't get any video signal unless I boot a Linux kernel. I
>> get no video signal in the EFI firmware, in the menu when I hold the cmd (or
>> left alt) key during boot, in the grub menu, and in OS X.  So the computer
>> is now damaged and unusable until a Linux kernel is loaded.  I have no idea
>> what exactly caused this, but I'm using this Mac for more than a year now,
>> and used another Mac mini Core Duo a few years before this, and never got
>> such behaviour.  The only thing I did was to install and use grub-efi-ia32
>> 1.98+20100705-1.  I used grub-efi-ia32 1.98 before.
> Can anyone on grub-devel comment on this?  It seems remarkable that we
> could be breaking video for future boots, and I wouldn't know where to
> start looking.
It's possible that some video registers are preserved accross soft
reboots. Buggy firmware may be unable to restore these registers to
working state. Try disconnecting power completely. There are 3 possible
reasons for registers to be messed up:
1) Bug in Firmware GOP or UGA implementation
2) GRUB accidently writing registers in UGA implementation (detection of
fb parameters is tricky)
3) Linux messes up the registers because started in another mode (try
> (Full configuration details at

Vladimir 'φ-coder/phcoder' Serbinenko

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