[Bug 81647] [hsw bisected] flickering blurry screen, prefer fast over wide dp link param

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81647

--- Comment #6 from Adam Jirasek <libm3l at gmail.com> ---
(In reply to comment #5)
> (In reply to comment #4)
> > (In reply to comment #3)
> > > Note this is a case where the earlier regression triumphs, and so this bug
> > > must persist until the root cause is known (i.e. we can fix this without
> > > breaking working machines).
> > 
> > Is there anything I can do to help?
> 
> I presume this is the laptop panel. Please try this patch:
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index d7fc2c0e9ba8..f4248d7f64f9 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -889,23 +889,13 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  			bpp = dev_priv->vbt.edp_bpp;
>  		}
>  
> -		if (IS_BROADWELL(dev)) {
> -			/* Yes, it's an ugly hack. */
> -			min_lane_count = max_lane_count;
> -			DRM_DEBUG_KMS("forcing lane count to max (%u) on BDW\n",
> -				      min_lane_count);
> -		} else if (dev_priv->vbt.edp_lanes) {
> -			min_lane_count = min(dev_priv->vbt.edp_lanes,
> -					     max_lane_count);
> -			DRM_DEBUG_KMS("using min %u lanes per VBT\n",
> -				      min_lane_count);
> -		}
> -
> -		if (dev_priv->vbt.edp_rate) {
> -			min_clock = min(dev_priv->vbt.edp_rate >> 3, max_clock);
> -			DRM_DEBUG_KMS("using min %02x link bw per VBT\n",
> -				      bws[min_clock]);
> -		}
> +		/*
> +		 * Use the maximum clock and number of lanes the eDP panel
> +		 * advertizes being capable of. Typically these values
> +		 * correspond to the native resolution of the panel.
> +		 */
> +		min_lane_count = max_lane_count;
> +		min_clock = max_clock;
>  	}
>  
>  	for (; bpp >= 6*3; bpp -= 2*3) {


Yes, this is a laptop. 
Your patch is working, I used the drm-intel-nightly (2014y-09m-03d-15h-44m-26s 
 SHA1 ID: 4144c90b76dfe6eaa2205ac947090786b5091cff) for testing

Thanks

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