[Intel-gfx] [PATCH] drm/i915: Fix broken mst get_hw_state.

[Ander Conselvan De Oliveira]

On Thu, 2015-08-27 at 13:13 +0200, Maarten Lankhorst wrote:
> connector->encoder is initialized as NULL. Fix this by setting it in
> during pre enable. MST connectors are not read out during initial hw
> readout, and have no fixed encoder mappings. So it's harmless to
> return false when the connector has never been assigned to an encoder.
>    
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 738178a0ac96..e3922d973db0 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6283,7 +6283,7 @@ static void intel_connector_check_state(struct intel_connector *connector)
>  		      connector->base.name);
>  
>  	if (connector->get_hw_state(connector)) {
> -		struct drm_encoder *encoder = &connector->encoder->base;
> +		struct intel_encoder *encoder = connector->encoder;
>  		struct drm_connector_state *conn_state = connector->base.state;
>  
>  		I915_STATE_WARN(!crtc,
> @@ -6295,13 +6295,13 @@ static void intel_connector_check_state(struct intel_connector *connector)
>  		I915_STATE_WARN(!crtc->state->active,
>  		      "connector is active, but attached crtc isn't\n");
>  
> -		if (!encoder)
> +		if (!encoder || encoder->type == INTEL_OUTPUT_DP_MST)
>  			return;
>  
> -		I915_STATE_WARN(conn_state->best_encoder != encoder,
> +		I915_STATE_WARN(conn_state->best_encoder != &encoder->base,
>  			"atomic encoder doesn't match attached encoder\n");
>  
> -		I915_STATE_WARN(conn_state->crtc != encoder->crtc,
> +		I915_STATE_WARN(conn_state->crtc != encoder->base.crtc,
>  			"attached encoder crtc differs from connector crtc\n");
>  	} else {
>  		I915_STATE_WARN(crtc && crtc->state->active,
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index ebf205462631..d606721b1788 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -159,6 +159,11 @@ static void intel_mst_pre_enable_dp(struct intel_encoder *encoder)
>  		return;
>  	}
>  
> +	/* MST encoders are bound to a crtc, not to a connector,
> +	 * force the mapping here for get_hw_state.
> +	 */
> +	found->encoder = encoder;
> +
>  	DRM_DEBUG_KMS("%d\n", intel_dp->active_mst_links);
>  	intel_mst->port = found->port;
>  
> @@ -392,7 +397,7 @@ static const struct drm_encoder_funcs intel_dp_mst_enc_funcs = {
>  
>  static bool intel_dp_mst_get_hw_state(struct intel_connector *connector)
>  {
> -	if (connector->encoder) {
> +	if (connector->encoder && connector->base.state->crtc) {

Is this here to cover the case where we disable this connector and assign the encoder to a different
connector? I guess this should work since if we disable the connector than crtc will be null, and
we'll assign a proper encoder when re-enabling. But now I'm wondering if it would make sense to set
connector->encoder back to NULL in post_disable.

Ander

>  		enum pipe pipe;
>  		if (!connector->encoder->get_hw_state(connector->encoder, &pipe))
>  			return false;
> 
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