Re: [PATCH] drm/mediatek: fix crtc index computation

[CK Hu <ck.hu@mediatek.com>]

Hi, Fabien:

On Mon, 2022-05-30 at 16:24 +0200, Fabien Parent wrote:
> The code always assume that the main path is enabled, which is not
> always the case. When the main path is not enabled, the CRTC index
> of the ext path is incorrect which makes the secondary path
> not usable. Fix the CRTC index calculation.
> 
> Signed-off-by: Fabien Parent <fparent@baylibre.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 46 +++++++++++++++--
> ----
>  1 file changed, 34 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> index 5d7504a72b11..6f2abfc608fb 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> @@ -430,25 +430,47 @@ int mtk_ddp_comp_get_id(struct device_node
> *node,
>  	return -EINVAL;
>  }
>  
> +static bool mtk_drm_comp_is_enabled(struct drm_device *drm,
> +				    const enum mtk_ddp_comp_id *path,
> +				    unsigned int path_len)
> +{
> +	struct mtk_drm_private *priv = drm->dev_private;
> +
> +	return path && path_len && !!priv->comp_node[path[path_len -
> 1]];

Why just check priv->comp_node[path[path_len - 1]]?
In mtk_drm_crtc_create(), crtc would not be created if any comp node in
the path is null.

Regards,
CK

> +}
> +
>  unsigned int mtk_drm_find_possible_crtc_by_comp(struct drm_device
> *drm,
>  						struct device *dev)
>  {
>  	struct mtk_drm_private *private = drm->dev_private;
> -	unsigned int ret = 0;
> +	unsigned int index = 0;
>  
> -	if (mtk_drm_find_comp_in_ddp(dev, private->data->main_path,
> private->data->main_len,
> +	if (mtk_drm_find_comp_in_ddp(dev, private->data->main_path,
> +				     private->data->main_len,
>  				     private->ddp_comp))
> -		ret = BIT(0);
> -	else if (mtk_drm_find_comp_in_ddp(dev, private->data->ext_path,
> -					  private->data->ext_len,
> private->ddp_comp))
> -		ret = BIT(1);
> -	else if (mtk_drm_find_comp_in_ddp(dev, private->data-
> >third_path,
> -					  private->data->third_len,
> private->ddp_comp))
> -		ret = BIT(2);
> -	else
> -		DRM_INFO("Failed to find comp in ddp table\n");
> +		return BIT(index);
> +
> +	if (mtk_drm_comp_is_enabled(drm, private->data->main_path,
> +				    private->data->main_len))
> +		index++;
>  
> -	return ret;
> +	if (mtk_drm_find_comp_in_ddp(dev, private->data->ext_path,
> +				     private->data->ext_len,
> +				     private->ddp_comp))
> +		return BIT(index);
> +
> +	if (mtk_drm_comp_is_enabled(drm, private->data->ext_path,
> +				    private->data->ext_len))
> +		index++;
> +
> +	if (mtk_drm_find_comp_in_ddp(dev, private->data->third_path,
> +					  private->data->third_len,
> +					  private->ddp_comp))
> +		return BIT(index);
> +
> +	DRM_INFO("Failed to find comp in ddp table\n");
> +
> +	return 0;
>  }
>  
>  int mtk_ddp_comp_init(struct device_node *node, struct mtk_ddp_comp
> *comp,