Re: [PATCH v4 10/11] drm/atomic-helper: Re-order bridge chain pre-enable and post-disable

[Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>]

On 22/06/2024 14:09, Aradhya Bhatia wrote:
> Move the bridge pre_enable call before crtc enable, and the bridge
> post_disable call after the crtc disable.
>
> The sequence of enable after this patch will look like:
>
> 	bridge[n]_pre_enable
> 	...
> 	bridge[1]_pre_enable
>
> 	crtc_enable
> 	encoder_enable
>
> 	bridge[1]_enable
> 	...
> 	bridge[n]__enable
>
> and vice-versa for the bridge chain disable sequence.
>
> The definition of bridge pre_enable hook says that,
> "The display pipe (i.e. clocks and timing signals) feeding this bridge
> will not yet be running when this callback is called".
>
> Since CRTC is also a source feeding the bridge, it should not be enabled
> before the bridges in the pipeline are pre_enabled. Fix that by
> re-ordering the sequence of bridge pre_enable and bridge post_disable.
>
> Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx>
> ---
>   drivers/gpu/drm/drm_atomic_helper.c | 165 ++++++++++++++++++----------
>   include/drm/drm_atomic_helper.h     |   7 ++
>   2 files changed, 114 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fb97b51b38f1..e8ad08634f58 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -74,6 +74,7 @@
>    * also shares the &struct drm_plane_helper_funcs function table with the plane
>    * helpers.
>    */
> +

Extra change.

>   static void
>   drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
>   				struct drm_plane_state *old_plane_state,
> @@ -1122,11 +1123,11 @@ crtc_needs_disable(struct drm_crtc_state *old_state,
>   }
>   
>   static void
> -disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
> +disable_encoder_brige_chain(struct drm_device *dev, struct drm_atomic_state *old_state,
> +			    enum bridge_chain_operation_type op_type)
>   {
>   	struct drm_connector *connector;
>   	struct drm_connector_state *old_conn_state, *new_conn_state;
> -	struct drm_crtc *crtc;
>   	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
>   	int i;
>   
> @@ -1163,32 +1164,55 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>   		if (WARN_ON(!encoder))
>   			continue;
>   
> -		funcs = encoder->helper_private;
> -
> -		drm_dbg_atomic(dev, "disabling [ENCODER:%d:%s]\n",
> -			       encoder->base.id, encoder->name);
> -
>   		/*
>   		 * Each encoder has at most one connector (since we always steal
>   		 * it away), so we won't call disable hooks twice.
>   		 */
>   		bridge = drm_bridge_chain_get_first_bridge(encoder);
> -		drm_atomic_bridge_chain_disable(bridge, old_state);
>   
> -		/* Right function depends upon target state. */
> -		if (funcs) {
> -			if (funcs->atomic_disable)
> -				funcs->atomic_disable(encoder, old_state);
> -			else if (new_conn_state->crtc && funcs->prepare)
> -				funcs->prepare(encoder);
> -			else if (funcs->disable)
> -				funcs->disable(encoder);
> -			else if (funcs->dpms)
> -				funcs->dpms(encoder, DRM_MODE_DPMS_OFF);
> -		}
> +		switch (op_type) {
> +		case DRM_ENCODER_BRIDGE_DISABLE:
> +			funcs = encoder->helper_private;
> +
> +			drm_dbg_atomic(dev, "disabling [ENCODER:%d:%s]\n",
> +				       encoder->base.id, encoder->name);
> +
> +			drm_atomic_bridge_chain_disable(bridge, old_state);
> +
> +			/* Right function depends upon target state. */
> +			if (funcs) {
> +				if (funcs->atomic_disable)
> +					funcs->atomic_disable(encoder, old_state);
> +				else if (new_conn_state->crtc && funcs->prepare)
> +					funcs->prepare(encoder);
> +				else if (funcs->disable)
> +					funcs->disable(encoder);
> +				else if (funcs->dpms)
> +					funcs->dpms(encoder, DRM_MODE_DPMS_OFF);
> +			}
> +
> +			break;
> +
> +		case DRM_BRIDGE_POST_DISABLE:
> +			drm_atomic_bridge_chain_post_disable(bridge, old_state);
>   
> -		drm_atomic_bridge_chain_post_disable(bridge, old_state);
> +			break;
> +
> +		default:
> +			drm_err(dev, "Unrecognized Encoder/Bridge Operation (%d).\n", op_type);
> +			break;
> +		}
>   	}
> +}
> +
> +static void
> +disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
> +	int i;
> +
> +	disable_encoder_brige_chain(dev, old_state, DRM_ENCODER_BRIDGE_DISABLE);
>   
>   	for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
>   		const struct drm_crtc_helper_funcs *funcs;
> @@ -1234,6 +1258,8 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>   		if (ret == 0)
>   			drm_crtc_vblank_put(crtc);
>   	}
> +
> +	disable_encoder_brige_chain(dev, old_state, DRM_BRIDGE_POST_DISABLE);
>   }
>   
>   /**
> @@ -1445,6 +1471,64 @@ static void drm_atomic_helper_commit_writebacks(struct drm_device *dev,
>   	}
>   }
>   
> +static void
> +enable_encoder_brige_chain(struct drm_device *dev, struct drm_atomic_state *old_state,
> +			   enum bridge_chain_operation_type op_type)
> +{
> +	struct drm_connector *connector;
> +	struct drm_connector_state *new_conn_state;
> +	int i;
> +
> +	for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
> +		const struct drm_encoder_helper_funcs *funcs;
> +		struct drm_encoder *encoder;
> +		struct drm_bridge *bridge;
> +
> +		if (!new_conn_state->best_encoder)
> +			continue;
> +
> +		if (!new_conn_state->crtc->state->active ||
> +		    !drm_atomic_crtc_needs_modeset(new_conn_state->crtc->state))
> +			continue;
> +
> +		encoder = new_conn_state->best_encoder;
> +
> +		/*
> +		 * Each encoder has at most one connector (since we always steal
> +		 * it away), so we won't call enable hooks twice.
> +		 */
> +		bridge = drm_bridge_chain_get_first_bridge(encoder);
> +
> +		switch (op_type) {
> +		case DRM_BRIDGE_PRE_ENABLE:
> +			drm_atomic_bridge_chain_pre_enable(bridge, old_state);
> +			break;
> +
> +		case DRM_ENCODER_BRIDGE_ENABLE:
> +			funcs = encoder->helper_private;
> +
> +			drm_dbg_atomic(dev, "enabling [ENCODER:%d:%s]\n",
> +				       encoder->base.id, encoder->name);
> +
> +			if (funcs) {
> +				if (funcs->atomic_enable)
> +					funcs->atomic_enable(encoder, old_state);
> +				else if (funcs->enable)
> +					funcs->enable(encoder);
> +				else if (funcs->commit)
> +					funcs->commit(encoder);
> +			}
> +
> +			drm_atomic_bridge_chain_enable(bridge, old_state);
> +			break;
> +
> +		default:
> +			drm_err(dev, "Unrecognized Encoder/Bridge Operation (%d).\n", op_type);
> +			break;
> +		}
> +	}
> +}
> +
>   /**
>    * drm_atomic_helper_commit_modeset_enables - modeset commit to enable outputs
>    * @dev: DRM device
> @@ -1465,10 +1549,10 @@ void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
>   	struct drm_crtc *crtc;
>   	struct drm_crtc_state *old_crtc_state;
>   	struct drm_crtc_state *new_crtc_state;
> -	struct drm_connector *connector;
> -	struct drm_connector_state *new_conn_state;
>   	int i;
>   
> +	enable_encoder_brige_chain(dev, old_state, DRM_BRIDGE_PRE_ENABLE);
> +
>   	for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
>   		const struct drm_crtc_helper_funcs *funcs;
>   
> @@ -1491,42 +1575,7 @@ void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
>   		}
>   	}
>   
> -	for_each_new_connector_in_state(old_state, connector, new_conn_state, i) {
> -		const struct drm_encoder_helper_funcs *funcs;
> -		struct drm_encoder *encoder;
> -		struct drm_bridge *bridge;
> -
> -		if (!new_conn_state->best_encoder)
> -			continue;
> -
> -		if (!new_conn_state->crtc->state->active ||
> -		    !drm_atomic_crtc_needs_modeset(new_conn_state->crtc->state))
> -			continue;
> -
> -		encoder = new_conn_state->best_encoder;
> -		funcs = encoder->helper_private;
> -
> -		drm_dbg_atomic(dev, "enabling [ENCODER:%d:%s]\n",
> -			       encoder->base.id, encoder->name);
> -
> -		/*
> -		 * Each encoder has at most one connector (since we always steal
> -		 * it away), so we won't call enable hooks twice.
> -		 */
> -		bridge = drm_bridge_chain_get_first_bridge(encoder);
> -		drm_atomic_bridge_chain_pre_enable(bridge, old_state);
> -
> -		if (funcs) {
> -			if (funcs->atomic_enable)
> -				funcs->atomic_enable(encoder, old_state);
> -			else if (funcs->enable)
> -				funcs->enable(encoder);
> -			else if (funcs->commit)
> -				funcs->commit(encoder);
> -		}
> -
> -		drm_atomic_bridge_chain_enable(bridge, old_state);
> -	}
> +	enable_encoder_brige_chain(dev, old_state, DRM_ENCODER_BRIDGE_ENABLE);
>   
>   	drm_atomic_helper_commit_writebacks(dev, old_state);
>   }
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index 9aa0a05aa072..b45a175a9f8a 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -43,6 +43,13 @@
>    */
>   #define DRM_PLANE_NO_SCALING (1<<16)
>   
> +enum bridge_chain_operation_type {
> +	DRM_BRIDGE_PRE_ENABLE,
> +	DRM_BRIDGE_POST_DISABLE,
> +	DRM_ENCODER_BRIDGE_ENABLE,
> +	DRM_ENCODER_BRIDGE_DISABLE,
> +};

Why are the last two "DRM_ENCODER"?

I don't like the enum... Having "enum bridge_chain_operation_type" as a 
parameter to a function looks like one can pass any of the enum's 
values, which is not the case.

How about an enum with just two values:

DRM_BRIDGE_PRE_ENABLE_POST_DISABLE
DRM_BRIDGE_ENABLE_DISABLE

 Tomi