[Intel-gfx] [PATCH v6 3/3] drm/i915: DP channel EQ check for use of DP link training optimization

[Ville Syrjälä]

On Tue, Jan 05, 2016 at 03:50:02PM +0200, Mika Kahola wrote:
> Don't use DP link training optimization if channel EQ is not ok. It has
> been reported that in case of failure in channel EQ check the link training
> optimization can be enabled and therefore may not be able to reuse the
> previously computed drive current and pre-emphasis levels.
> 
> v2: Added MST case (Ville)
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91393
> Signed-off-by: Mika Kahola <mika.kahola at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 3137187..c995dbd 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4254,6 +4254,7 @@ go_again:
>  			if (intel_dp->active_mst_links &&
>  			    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
>  				DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
> +				intel_dp->train_set_valid = false;
>  				intel_dp_start_link_train(intel_dp);
>  				intel_dp_stop_link_train(intel_dp);
>  			}
> @@ -4354,6 +4355,7 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
>  		(!drm_dp_channel_eq_ok(link_status, intel_dp->lane_count))) {
>  		DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
>  			      intel_encoder->base.name);
> +		intel_dp->train_set_valid = false;
>  		intel_dp_start_link_train(intel_dp);
>  		intel_dp_stop_link_train(intel_dp);
>  	}
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC