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

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

[Colin Watson]

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.

(Full configuration details at
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=588208.)

-- 
Colin Watson                                       [cjwatson@ubuntu.com]

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

[Isaac Dupree]

On 07/06/10 04:54, Colin Watson wrote:
> 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.
>
> (Full configuration details at
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=588208.)

I'm tempted to ask (but you probably shouldn't try it!*), what if you 
clear the BIOS/EFI state (NVRAM) in case it's been corrupted somehow 
relevant --
hold Command-Option-P-R while booting
http://support.apple.com/kb/ht1533
*WARNING! If it doesn't fix the problem, then you obviously still won't 
be able to see... and, however it was configured such that GRUB would 
automatically be booted is likely to be broken now, leading to 
unhappiness :-(

(A safer way to investigate this thought would be to dump the contents 
of your NVRAM and upload it and compare it to what the default state 
looks like, if anyone knows how to do that?)

Does booting from a Linux LiveCD give you graphics?  (via grub or refit 
or holding 'c' when you boot) -- both as some sort of failsafe, and it 
*might* give us a bit of information. (disclaimer: I don't develop grub2 
so far, I just use it [on my Macbook, using grub2 BIOS based since I 
haven't gotten grub2 EFI to boot Linux very well yet], and read the 
mailing-list)

-Isaac

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

[Tino Keitel]

On Tue, Jul 06, 2010 at 15:04:25 -0400, Isaac Dupree wrote:

[...]

> I'm tempted to ask (but you probably shouldn't try it!*), what if
> you clear the BIOS/EFI state (NVRAM) in case it's been corrupted
> somehow relevant --
> hold Command-Option-P-R while booting
> http://support.apple.com/kb/ht1533

I have a PC keyboard, and tried windows-alt-p-r. According to Apple
documentation, I should hear 2 beeps, but I don't, so I'm not sure if I
did it right.

I also found a way to restore the video in OS X. After a suspend and
resume the video is OK, until the next reboot. So I tried "nvram -c" in
a terminal. I don't know if this does the same, but it didn't help.

Regards,
Tino

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

[Vladimir 'φ-coder/phcoder' Serbinenko]

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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
gfxpayload)
> (Full configuration details at
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=588208.)
>
>   


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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

[Tino Keitel]

Hi,

just FYI, I tried again the instructions to reset the PMU, SMC and run
nvram -c, changed video resolution settings in OS X, and at the end I
got working video back. *phew*

Thanks for your help and regards,
Tino

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

[Isaac Dupree]

On 07/06/10 16:52, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> 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.

And wait a few minutes to improve chances that capacitors and other 
persistent electrical effects discharge/randomize!  (At least, there's a 
similar effect with my laptop's built-in webcam)

-Isaac