Bug#565160: Linux console garbled after experimental grub-pc boot

[Jonathan Nieder]

Yves-Alexis Perez wrote:
> Le 20/01/2010 12:09, Jonathan Nieder a écrit :
>> Yves-Alexis Perez wrote:
>> 
>>> [    0.000000] Console: colour dummy device 80x25
>> 
>> So the VGA console was not initialized.
>
> Might it be related to the fact I use KMS?

Maybe.  If so, then our symptoms must come from different causes.
(I am not using KMS.)

That does seem possible.  Consider:

 - you are using 2.6.32-trunk -5, Intel graphics, seems to try to
   switch modes but the screen remains black until X starts.

[    0.397178] vesafb: framebuffer at 0xd0000000, mapped to 0xffffc90010980000, using 7552k, total 7552k
[    0.397182] vesafb: mode is 1600x1200x32, linelength=6400, pages=0
[    0.397185] vesafb: scrolling: redraw
[    0.397188] vesafb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[    0.499776] Console: switching to colour frame buffer device 200x75
[    0.602218] fb0: VESA VGA frame buffer device
[    1.304414] fb: conflicting fb hw usage inteldrmfb vs VESA VGA - removing generic driver
[    1.304567] fb1: inteldrmfb frame buffer device
[    1.304570] registered panic notifier
[    1.304592] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0
[   35.335041] [drm] DAC-6: set mode 1920x1200 21

 - I tried 2.6.33-rc4-00399-g24bc734 and recent linux-next, fairly
   old ATI graphics with no KMS support, framebuffer driver not loaded
   in kernel, boot menu remains on screen, no attempted mode switch
   shown in the kernel log.

   When I just tried 2.6.32-trunk -5, the console looked okay!  (But
   the boot does not finish because the root filesystem, which uses ext4,
   does not get mounted for some reason.  This happens regardless of the
   version of grub I use.)

 - Jussi gets a black screen with 2.6.32-trunk -5, which tries to use
   vesafb to draw the console; but gets a working console with 2.6.33-rc4
   using inteldrmfb.

All this seems to suggest there are three things going on:

 - grub leaves the GPU in a graphical mode

 - vesafb can’t use it or switch out of it

 - various KMS drivers _can_ switch out of it, though

 - without a framebuffer driver, Linux can’t switch out of it.

grub’s behavior here might not even be a bad thing (it would avoid
flicker, maybe), except that some Linux drivers can’t handle it.

But I am only grasping at straws here.

Jonathan