Re: [PATCH] drm/i915/edp: use lane count and link rate from DPCD for eDP

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Sep 09, 2014 at 11:25:13AM +0300, Jani Nikula wrote:
> eDP panels are generally designed to support only a single clock and
> lane configuration.
> 
> commit 56071a207602a451f0c46d3dcc8379b59ef576e2
> Author: Jani Nikula <jani.nikula@intel.com>
> Date:   Tue May 6 14:56:52 2014 +0300
> 
>     drm/i915: use lane count and link rate from VBT as minimums for eDP
> 
> should have started using the optimal link parameters for eDP
> panels. Turns out a certain other OS uses DPCD instead of VBT, which
> means trusting VBT on this may not be so reliable after all. Follow
> suit.

Oh well, let's dare the edp lords a bit and merge this to dinq.

/me closes the hatch of the bunker and hunxches down
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81647
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79386

Please add the Tested-by: lines gathered from bugzilla next time around.
I've fixed that.

> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Thanks, Daniel

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index ab7cd0a75bd5..72bf533596c8 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1068,23 +1068,15 @@ 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. The panels are generally
> +		 * designed to support only a single clock and lane
> +		 * configuration, and 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) {
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch