linux-kernel - Re: [Regression: 2.6.25-rc5: Blank Screen: Intel 945]

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Message-Id: <200803141029.38124.jbarnes@virtuousgeek.org>
Date:	Fri, 14 Mar 2008 10:29:38 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Justin Madru <jdm64@...ab.com>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [Regression: 2.6.25-rc5: Blank Screen: Intel 945]

On Thursday, March 13, 2008 9:22 pm Justin Madru wrote:
> Jesse Barnes wrote:
> > Well, the blank screen is probably due to a pipe programming timing
> > problem. IGD devices have been getting less & less sensitive to it over
> > time (830s would hang if you looked at them the wrong way) but it's still
> > not that hard to mis-program them.
> >
> > Can you narrow down the problem at all?  Did it occur just after a kernel
> > upgrade?  Or did you also upgrade your X driver?  There haven't been any
> > real changes in intelfb since Oct. when Krzysztof added interlaced mode
> > support, so it's weird that you're just seeing problems now...
>
> Not that I can think of. Other than a custom kernel I use standard
> Ubuntu 7.10. I was testing out the kernel starting with 2.6.23-rc4 and
> I've tested each rc, recompiling when a new one came out (except for rc1
> and rc2, they didn't compile). So, when 2.6.25-rc3 came out I recompiled
> and came across this error.

It would be interesting if you could get register dumps at a couple of 
different points, using the intel_reg_dumper tool in 
git://git.freedesktop.org/git/xorg/driver/xf86-video-intel (in 
src/reg_dumper).  You'll probably have to modify your boot scripts though.  
It would be good to get them:
  - at startup time before the splash screen
  - sometime while the splash screen is running
  - after X starts and you see the blank screen

Since I think this is actually an X driver bug, can you file a bug at 
freedesktop.org and attach the register dumps there?

>
> I've removed all fb devices and the blank screen _almost_ never happens
> (also, I _don't_ have to disable the splash screen). There is one
> _big_exception_ the problem still happens when I'm at my University (and
> _very_ consistently). There, I have to disable the splash screen, and
> that ~mostly~ fixes the problem.

What's different between your Uni. environment and your home environment?

> I can't believe it could be related, but when I boot the computer at the
> Univ. I get a flood of kernel messages  related to the wireless all the
>
> time, but still connect:
>  > kernel: wlan0_rename: RX too short data frame payload
>
> _Could_ a wireless problem be related to a graphics's problem? I
> wouldn't think so? But, it would explain why I get the blank screen
> mostly when I get the wireless problem. But, then again it could be
> another problem altogether.

Well, it's possible that the wireless issue is affecting the pipe programming 
timing enough to expose the bug (stuff like this is usually a problem with 
either not waiting for a register program to take effect and/or programming 
the regs in the wrong order).

> > I think the only thing you'll lose is the boot splash screen.
>
> I did disable fb correctly right? Because I still have a boot splash
> screen.

Yeah, looks like it's off.  Ubuntu may be falling back to using the X vesa 
driver or something though...

Jesse
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