[Intel-gfx] Trouble with dell latitude E6420

[Takashi Iwai]

At Mon, 2 Jul 2012 10:54:43 +0200,
Georg Grabler wrote:
> 
> I've had this problem with the e6420 on 1600x900. Applying your work
> around fixed it for me. Though, kernel 3.5-rc4 fixes the problem "for
> real" (it even fixes the default resolutions set when X comes up,
> which did not work properly before).

OK.  So far, my assumption looks correct.

> I'm not aware of what this could cause to other resolutions than
> 1600x900, that's why i did not recommend Chakra to apply the patch.

Well, the only question is the native resolution of the panel.

If it ever happens with a panel lower than 1600x900 resolution, it
means that the fix should be applied to all panels.  If it happens
only with such higher ones, it's likely an issue with HD+ panel
dual-channel mode, and the workaround should be applied in a limited
manner.


thanks,

Takashi

> 
> Kind regards,
> Georg
> 
> On Mon, Jul 2, 2012 at 10:18 AM, Takashi Iwai <tiwai at suse.de> wrote:
> > 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
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>