[Intel-gfx] Trouble with dell latitude E6420

[Takashi Iwai]

At Thu, 28 Jun 2012 14:23:04 -0400,
Giacomo Comes wrote:
> 
> On Thu, Jun 28, 2012 at 07:52:18AM +0200, Takashi Iwai wrote:
> > At Tue, 26 Jun 2012 15:08:32 -0400,
> > Giacomo Comes wrote:
> > > 
> > > I have a dell latitude E6420 with Sandybridge Mobile (GT2).
> > > Since I got it (about one year ago), it has been a nightmare to run linux on it.
> > > At the beginning I installed openSUSE 11.4 (kernel 2.6.37.6) and the laptop
> > > would freeze almost immediately. After that I waited for newer kernels in order to
> > > see if things would improve. They did improve indeed and finally with kernel 3.0
> > > I was able to run linux (openSUSE 11.4) without laptop freeze or screen issue.
> > > Unfortunately, the only kernel that works with my laptop is 3.0. Newer kernel
> > > (3.1, 3.2, 3.3 and 3.4) do not work.
> > > This is what happen if I run kernel 2.6.39, 3.1, 3.2, 3.3 and 3.4:
> > > The laptop boot and does the boot process fine. At the end of the boot process X
> > > starts and here the problem appears (about 50% of the times):
> > > the screen goes black on the left side (about 2/3 of the whole screen) with white
> > > stripes to the right side (the remaining 1/3).
> > > The laptop is not dead: I can remotely login or I can perform a clean shutdown
> > > if I press the power button, but the screen is totally dead.
> > > Another strange issue is that after a bad boot (with the black screen) at the
> > > next reboot the screen will start to flicker. The flickering will last some time
> > > and it will become less intense as the time goes until it will disappear completely.
> > > The funny thing is that the intensity of flicker depends on how long I keep the
> > > black screen. If, after the boot process, the black screen appears and I reboot
> > > the laptop immediately, then the flicked is moderate and it disappear after
> > > 1 or 2 minutes. If I keep the black screen for 1 minute or more, then after the
> > > reboot the flicker is very intense and it takes much more to fade.
> > 
> > This reminds me of a similar bug I've seen on HP laptops with HD+
> > (1600x900) monitors.  Could you check whether the patch below helps?
> > 
> > Note that it just avoids entering to the wrong mode.  If your laptop
> > already starts flickering, at first recover from the flickering state,
> > apply the patch, and reboot/test.
> > 
> > 
> > Takashi
> > 
> > ---
> > diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
> > index 08eb04c..3f61bba 100644
> > --- a/drivers/gpu/drm/i915/intel_lvds.c
> > +++ b/drivers/gpu/drm/i915/intel_lvds.c
> > @@ -413,7 +413,7 @@ static void intel_lvds_prepare(struct drm_encoder *encoder)
> >  	 * the panel fitter. However at all other times we can just reset
> >  	 * the registers regardless.
> >  	 */
> > -	if (!HAS_PCH_SPLIT(encoder->dev) && intel_lvds->pfit_dirty)
> > +	/*if (!HAS_PCH_SPLIT(encoder->dev) && intel_lvds->pfit_dirty)*/
> >  		intel_lvds_disable(intel_lvds);
> >  }
> >  
> 
> This patch seems to fix the problem. I will regularly run a kernel with 
> this patch and report if I see any other issue.

Which native resolution does your machine have?
If it's 1600x900 or such, we may consider to apply the workaround
generically for such resolutions.  AFAIK, all the HP machines affected
by this symptom have 1600x900 panels (but different panel vendors).


thanks,

Takashi