[Intel-gfx] KMS breaks console

Eric Anholt eric at anholt.net
Tue Feb 3 21:27:52 CET 2009

On Tue, 2009-02-03 at 20:26 +0100, Lukas Hejtmanek wrote:
> On Tue, Feb 03, 2009 at 10:35:40AM -0800, Jesse Barnes wrote:
> > > does this mean that oldschool text console is no longer supported as long
> > > as KMS is stream? Too bad I think.
> > 
> > Once you go into a graphics mode, yes.  Why too bad?
> maybe because the text mode is more stable and seems to be much faster at
> lower CPU utilization?

Stable?  kill -9 your X Server right now -- does it go back to something
sane?  No.

Now start up an X Server again and exit -- does it ever recover?  Not

Even in normal circumstances we have a *terrible* time getting back to
text mode.  My laptop fails at switching back around 20% of the time.  A
lot of SDVO users still can't get back to text mode, because getting
those mode switches right is such a pain.  I think pre-915 users are in
an even worse position.  This has been the case for the history of linux
graphics -- I remember longstanding problems with it when I was working
on radeon, and when I was working on matrox before that, and when I was
working on 3dfx before that.

Switching from graphics to console will become stable when it doesn't
involve switching back to text mode.

Making the fb console actually fast enough -- that's just a matter of
doing the same thing that real graphical terminals do and limiting the
framerate of output.

Eric Anholt
eric at anholt.net                         eric.anholt at intel.com

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