Re: [PATCH 8/9] drm: rcar-du: Skip encoder allocation for LVDS1 in dual-link mode

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Hi Laurent,

On 04/12/2020 22:01, Laurent Pinchart wrote:
> The rcar-du driver skips registration of the encoder for the LVDS1
> output when LVDS is used in dual-link mode, as the LVDS0 and LVDS1 links
> are bundled and handled through the LVDS0 output. It however still
> allocates the encoder and immediately destroys it, which is pointless.
> Skip allocation of the encoder altogether in that case.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

I love it when re-ordering code simplifies all the error conditions.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

> ---
>  drivers/gpu/drm/rcar-du/rcar_du_encoder.c | 51 ++++++++++-------------
>  1 file changed, 22 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_encoder.c b/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> index e4f35a88d00f..49c0b27e2f5a 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> @@ -65,17 +65,6 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
>  	struct drm_bridge *bridge;
>  	int ret;
>  
> -	renc = kzalloc(sizeof(*renc), GFP_KERNEL);
> -	if (renc == NULL)
> -		return -ENOMEM;
> -
> -	rcdu->encoders[output] = renc;
> -	renc->output = output;
> -	encoder = rcar_encoder_to_drm_encoder(renc);
> -
> -	dev_dbg(rcdu->dev, "initializing encoder %pOF for output %u\n",
> -		enc_node, output);
> -
>  	/*
>  	 * Locate the DRM bridge from the DT node. For the DPAD outputs, if the
>  	 * DT node has a single port, assume that it describes a panel and
> @@ -86,23 +75,17 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
>  	    rcar_du_encoder_count_ports(enc_node) == 1) {
>  		struct drm_panel *panel = of_drm_find_panel(enc_node);
>  
> -		if (IS_ERR(panel)) {
> -			ret = PTR_ERR(panel);
> -			goto error;
> -		}
> +		if (IS_ERR(panel))
> +			return PTR_ERR(panel);
>  
>  		bridge = devm_drm_panel_bridge_add_typed(rcdu->dev, panel,
>  							 DRM_MODE_CONNECTOR_DPI);
> -		if (IS_ERR(bridge)) {
> -			ret = PTR_ERR(bridge);
> -			goto error;
> -		}
> +		if (IS_ERR(bridge))
> +			return PTR_ERR(bridge);
>  	} else {
>  		bridge = of_drm_find_bridge(enc_node);
> -		if (!bridge) {
> -			ret = -EPROBE_DEFER;
> -			goto error;
> -		}
> +		if (!bridge)
> +			return -EPROBE_DEFER;
>  
>  		if (output == RCAR_DU_OUTPUT_LVDS0 ||
>  		    output == RCAR_DU_OUTPUT_LVDS1)
> @@ -110,16 +93,26 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
>  	}
>  
>  	/*
> -	 * On Gen3 skip the LVDS1 output if the LVDS1 encoder is used as a
> -	 * companion for LVDS0 in dual-link mode.
> +	 * Create and initialize the encoder. On Gen3 skip the LVDS1 output if
> +	 * the LVDS1 encoder is used as a companion for LVDS0 in dual-link
> +	 * mode.
>  	 */
>  	if (rcdu->info->gen >= 3 && output == RCAR_DU_OUTPUT_LVDS1) {
> -		if (rcar_lvds_dual_link(bridge)) {
> -			ret = -ENOLINK;
> -			goto error;
> -		}
> +		if (rcar_lvds_dual_link(bridge))
> +			return -ENOLINK;
>  	}
>  
> +	renc = kzalloc(sizeof(*renc), GFP_KERNEL);
> +	if (renc == NULL)
> +		return -ENOMEM;
> +
> +	rcdu->encoders[output] = renc;
> +	renc->output = output;
> +	encoder = rcar_encoder_to_drm_encoder(renc);
> +
> +	dev_dbg(rcdu->dev, "initializing encoder %pOF for output %u\n",
> +		enc_node, output);
> +
>  	ret = drm_encoder_init(&rcdu->ddev, encoder, &rcar_du_encoder_funcs,
>  			       DRM_MODE_ENCODER_NONE, NULL);
>  	if (ret < 0)
> 

-- 
Regards
--
Kieran
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