Strange thing with framebuffer

[Lukasz Wiechec <lwiechec2@space.pl>]

Hi,

since I added `ywrap' parameter in my lilo.conf's  'video=vesa:ywrap', I
have notice strange behaviour: every now and then my screen get shifted
downwards by two lines (which makes bottom lines unreadable, as they are
"off the screen" then). After awhile those two lines dissapear and
everything comes back to normal. That happens quite regularly, so I
expect some cycle. 

The kernel documentation says this:

<snip>
  You can pass options to vesafb using "video=vesa:option" on
  the kernel command line.  Multiple options should be separated
  by comma, like this: "video=vesa:ypan,invers"

  Accepted options:

  invers	no comment...

  ypan	enable display panning using the VESA protected mode 
	interface.  The visible screen is just a window of the
	video memory, console scrolling is done by changing the
	start of the window.
	pro:	* scrolling (fullscreen) is fast, because there is
		  no need to copy around data.
		* You'll get scrollback (the Shift-PgUp thing),
		  the video memory can be used as scrollback buffer
	kontra: * scrolling only parts of the screen causes some
		  ugly flicker effects (boot logo flickers for
		  example).

  ywrap	Same as ypan, but assumes your gfx board can wrap-around 
	the video memory (i.e. starts reading from top if it
	reaches the end of video memory).  Faster than ypan.
<snip>

...has it anything to do with video memory and mtrr settings? To speed
things up, I'm using following command to set mtrr's (this is copied
from X settings; `mtrr' parameter passed to framebuffer driver was
setting my card as 4MB and it is 8MB):

#
# set MTRR registers
# now, this is supposed to speed thing up - while in console (X sets this by itself)
#
echo "base=0x40000000 size=0x800000 type=write-combining" >| /proc/mtrr



I wouldn't like to resign from `ywrap' options: it's fast and I'm
working in "text mode" (sic! as this is fb after all :-) a lot.

Big thanks in advance,



-- 
Lukasz