[Intel-gfx] Trouble with dell latitude E6420

[Giacomo Comes]

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.

Giacomo