Re: [PATCH v2.1 3/6] drm/atomic: Always call steal_encoder, v2.

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Mar 01, 2016 at 02:52:05PM +0100, Maarten Lankhorst wrote:
> There's no need to have a separate function to get the crtc
> which is stolen, this can already be found when actually
> stealing the encoder.
> 
> drm_for_each_connector already checks for connection_mutex, so
> use that macro now.
> 
> Changes since v1:
> - Do not check for NULL crtc in connector_state,
>   this may happen when a crtc is disabled and its encoder stolen.
> - Because of this, use connector->state->crtc instead of conn_state->crtc.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Also I think we should have a testcase of some sorts for this. Probably
simplest to write unit tests for the atomic helper library.
-Daniel

> ---
> Oops, this patch had a WARN_ON(!conn_state->crtc); in v1,
> this broke DP MST which had a legitimate reason to do so.
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 3d1f97a832fc..72ca85b32260 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -106,25 +106,6 @@ check_pending_encoder_assignment(struct drm_atomic_state *state,
>  	return true;
>  }
>  
> -static struct drm_crtc *
> -get_current_crtc_for_encoder(struct drm_device *dev,
> -			     struct drm_encoder *encoder)
> -{
> -	struct drm_mode_config *config = &dev->mode_config;
> -	struct drm_connector *connector;
> -
> -	WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
> -
> -	drm_for_each_connector(connector, dev) {
> -		if (connector->state->best_encoder != encoder)
> -			continue;
> -
> -		return connector->state->crtc;
> -	}
> -
> -	return NULL;
> -}
> -
>  static void
>  set_best_encoder(struct drm_atomic_state *state,
>  		 struct drm_connector_state *conn_state,
> @@ -168,38 +149,18 @@ set_best_encoder(struct drm_atomic_state *state,
>  
>  static int
>  steal_encoder(struct drm_atomic_state *state,
> -	      struct drm_encoder *encoder,
> -	      struct drm_crtc *encoder_crtc)
> +	      struct drm_encoder *encoder)
>  {
> -	struct drm_mode_config *config = &state->dev->mode_config;
>  	struct drm_crtc_state *crtc_state;
>  	struct drm_connector *connector;
>  	struct drm_connector_state *connector_state;
>  
> -	/*
> -	 * We can only steal an encoder coming from a connector, which means we
> -	 * must already hold the connection_mutex.
> -	 */
> -	WARN_ON(!drm_modeset_is_locked(&config->connection_mutex));
> -
> -	DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] in use on [CRTC:%d:%s], stealing it\n",
> -			 encoder->base.id, encoder->name,
> -			 encoder_crtc->base.id, encoder_crtc->name);
> +	drm_for_each_connector(connector, state->dev) {
> +		struct drm_crtc *encoder_crtc;
>  
> -	crtc_state = drm_atomic_get_crtc_state(state, encoder_crtc);
> -	if (IS_ERR(crtc_state))
> -		return PTR_ERR(crtc_state);
> -
> -	crtc_state->connectors_changed = true;
> -
> -	list_for_each_entry(connector, &config->connector_list, head) {
>  		if (connector->state->best_encoder != encoder)
>  			continue;
>  
> -		DRM_DEBUG_ATOMIC("Stealing encoder from [CONNECTOR:%d:%s]\n",
> -				 connector->base.id,
> -				 connector->name);
> -
>  		connector_state = drm_atomic_get_connector_state(state,
>  								 connector);
>  		if (IS_ERR(connector_state))
> @@ -208,7 +169,18 @@ steal_encoder(struct drm_atomic_state *state,
>  		if (connector_state->best_encoder != encoder)
>  			continue;
>  
> +		encoder_crtc = connector->state->crtc;
> +
> +		DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] in use on [CRTC:%d:%s], stealing it\n",
> +				 encoder->base.id, encoder->name,
> +				 encoder_crtc->base.id, encoder_crtc->name);
> +
>  		set_best_encoder(state, connector_state, NULL);
> +
> +		crtc_state = drm_atomic_get_existing_crtc_state(state, encoder_crtc);
> +		crtc_state->connectors_changed = true;
> +
> +		return 0;
>  	}
>  
>  	return 0;
> @@ -221,7 +193,6 @@ update_connector_routing(struct drm_atomic_state *state,
>  {
>  	const struct drm_connector_helper_funcs *funcs;
>  	struct drm_encoder *new_encoder;
> -	struct drm_crtc *encoder_crtc;
>  	struct drm_crtc_state *crtc_state;
>  	int idx, ret;
>  
> @@ -299,17 +270,12 @@ update_connector_routing(struct drm_atomic_state *state,
>  		return -EINVAL;
>  	}
>  
> -	encoder_crtc = get_current_crtc_for_encoder(state->dev,
> -						    new_encoder);
> -
> -	if (encoder_crtc) {
> -		ret = steal_encoder(state, new_encoder, encoder_crtc);
> -		if (ret) {
> -			DRM_DEBUG_ATOMIC("Encoder stealing failed for [CONNECTOR:%d:%s]\n",
> -					 connector->base.id,
> -					 connector->name);
> -			return ret;
> -		}
> +	ret = steal_encoder(state, new_encoder);
> +	if (ret) {
> +		DRM_DEBUG_ATOMIC("Encoder stealing failed for [CONNECTOR:%d:%s]\n",
> +				 connector->base.id,
> +				 connector->name);
> +		return ret;
>  	}
>  
>  	if (WARN_ON(!connector_state->crtc))
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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