https://bugzilla.kernel.org/show_bug.cgi?id=153401

--- Comment #39 from Luca Viggiani <lviggi...@gmail.com> ---
(In reply to Zhang Rui from comment #36)
> commit aeddda06c1a704bb97c8a7bfe7a472120193bd56
> Author: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Date:   Tue Jul 12 15:00:37 2016 +0300
> 
>     drm/i915: Ignore panel type from OpRegion on SKL
>     
>     Dell XPS 13 9350 apparently doesn't like it when we use the panel type
>     from OpRegion. The OpRegion panel type (0) tells us to use use low
>     vswing for eDP, whereas the VBT panel type (2) tells us to use normal
>     vswing. The problem is that low vswing results in some display flickers.
>     Since no one seems to know how this stuff is supposed to be handled,
>     let's just ignore the OpRegion panel type on SKL for now.
>     
>     v2: Print the panel type correctly in the debug output
>     
>     Reported-by: James Bottomley <james.bottom...@hansenpartnership.com>
>     Cc: James Bottomley <james.bottom...@hansenpartnership.com>
>     Cc: drm-intel-fi...@lists.freedesktop.org
>     References:
> https://lists.freedesktop.org/archives/intel-gfx/2016-June/098826.html
>     Fixes: a05628195a0d ("drm/i915: Get panel_type from OpRegion panel
> details")
>     Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
>     Link:
> http://patchwork.freedesktop.org/patch/msgid/1468324837-29237-1-git-send-
> email-ville.syrj...@linux.intel.com
>     Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>
>     Tested-by: James Bottomley <james.bottom...@hansenpartnership.com>
>     Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
>     (cherry picked from commit bb10d4ec3be4b069bfb61c60ca4f708f58f440f1)
>     [danvet: Fix up cherry-pick conflict with an s/dev_priv/dev/.]
>     Signed-off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> 
> diff --git a/drivers/gpu/drm/i915/intel_opregion.c
> b/drivers/gpu/drm/i915/intel_opregion.c
> index 99e2603..16e209d 100644
> --- a/drivers/gpu/drm/i915/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/intel_opregion.c
> @@ -1038,5 +1038,16 @@ intel_opregion_get_panel_type(struct drm_device *dev)
>                 return -ENODEV;
>         }
>  
> +       /*
> +        * FIXME On Dell XPS 13 9350 the OpRegion panel type (0) gives us
> +        * low vswing for eDP, whereas the VBT panel type (2) gives us normal
> +        * vswing instead. Low vswing results in some display flickers, so
> +        * let's simply ignore the OpRegion panel type on SKL for now.
> +        */
> +       if (IS_SKYLAKE(dev)) {
> +               DRM_DEBUG_KMS("Ignoring OpRegion panel type (%d)\n", ret -
> 1);
> +               return -ENODEV;
> +       }
> +
>         return ret - 1;
>  }
> 
> This seems to be something related, please check if your code contains this
> commit, if yes, please check if the problem still exists with the commit
> reverted, if no, please apply this and see if the problem still exists.

The patch is there. I've commented it out and I'm currently rebuilding kernel
package.
Once it finish I'll test it and let you know

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