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Date:   Tue, 21 Nov 2023 15:44:13 +0100
From:   Michael Walle <mwalle@kernel.org>
To:     =?UTF-8?Q?N=C3=ADcolas_F_=2E_R_=2E_A_=2E_Prado?= 
        <nfraprado@collabora.com>, Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
Cc:     "Nancy . Lin" <nancy.lin@mediatek.com>,
        Frank Wunderlich <frank-w@public-files.de>,
        Jitao Shi <jitao.shi@mediatek.com>,
        Stu Hsieh <stu.hsieh@mediatek.com>,
        dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        "Jason-JH.Lin" <jason-jh.lin@mediatek.com>
Subject: Re: [PATCH v4 2/2] drm/mediatek: dpi/dsi: fix possible_crtcs
 calculation
In-Reply-To: <20230905084922.3908121-2-mwalle@kernel.org>
References: <20230905084922.3908121-1-mwalle@kernel.org>
 <20230905084922.3908121-2-mwalle@kernel.org>
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Precedence: bulk

Hi,

> mtk_drm_find_possible_crtc_by_comp() assumed that the main path will
> always have the CRTC with id 0, the ext id 1 and the third id 2. This
> is only true if the paths are all available. But paths are optional 
> (see
> also comment in mtk_drm_kms_init()), e.g. the main path might not be
> enabled or available at all. Then the CRTC IDs will shift one up, e.g.
> ext will be 0 and the third path will be 1.
> 
> To fix that, dynamically calculate the IDs by the presence of the 
> paths.
> 
> While at it, make the return code a signed one and return -ENOENT if no
> path is found and handle the error in the callers.
> 
> Fixes: 5aa8e7647676 ("drm/mediatek: dpi/dsi: Change the getting 
> possible_crtc way")
> Suggested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> Signed-off-by: Michael Walle <mwalle@kernel.org>
> Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>

Is there anything wrong with these two patches? They are now lingering
around for more than two months.

Unfortunately, patch 2/2 won't apply anymore because of commit
01389b324c97 ("drm/mediatek: Add connector dynamic selection
capability). And I'm a bit puzzled for what the crtc_id is used
there because I guess it will have the same problem this patch
fixes.

-michael

> ---
> v4:
>  - return -ENOENT if mtk_drm_find_possible_crtc_by_comp() doesn't find
>    any path
> v3:
>  - use data instead of priv_n->data
>  - fixed typos
>  - collected Rb and Tb tags
> v2:
>  - iterate over all_drm_private[] to get any vdosys
>  - new check if a path is available
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c          |  5 +-
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 75 ++++++++++++++++-----
>  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h |  3 +-
>  drivers/gpu/drm/mediatek/mtk_dsi.c          |  5 +-
>  4 files changed, 68 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c 
> b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index 2f931e4e2b60..f9250f7ee706 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -796,7 +796,10 @@ static int mtk_dpi_bind(struct device *dev, struct 
> device *master, void *data)
>  		return ret;
>  	}
> 
> -	dpi->encoder.possible_crtcs = 
> mtk_drm_find_possible_crtc_by_comp(drm_dev, dpi->dev);
> +	ret = mtk_drm_find_possible_crtc_by_comp(drm_dev, dpi->dev);
> +	if (ret < 0)
> +		goto err_cleanup;
> +	dpi->encoder.possible_crtcs = ret;
> 
>  	ret = drm_bridge_attach(&dpi->encoder, &dpi->bridge, NULL,
>  				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c 
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> index 771f4e173353..83ae75ecd858 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> @@ -507,6 +507,27 @@ static bool mtk_drm_find_comp_in_ddp(struct device 
> *dev,
>  	return false;
>  }
> 
> +static bool mtk_ddp_path_available(const unsigned int *path,
> +				   unsigned int path_len,
> +				   struct device_node **comp_node)
> +{
> +	unsigned int i;
> +
> +	if (!path)
> +		return false;
> +
> +	for (i = 0U; i < path_len; i++) {
> +		/* OVL_ADAPTOR doesn't have a device node */
> +		if (path[i] == DDP_COMPONENT_DRM_OVL_ADAPTOR)
> +			continue;
> +
> +		if (!comp_node[path[i]])
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
>  int mtk_ddp_comp_get_id(struct device_node *node,
>  			enum mtk_ddp_comp_type comp_type)
>  {
> @@ -522,25 +543,47 @@ int mtk_ddp_comp_get_id(struct device_node *node,
>  	return -EINVAL;
>  }
> 
> -unsigned int mtk_drm_find_possible_crtc_by_comp(struct drm_device 
> *drm,
> -						struct device *dev)
> +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;
> -
> -	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");
> +	const struct mtk_mmsys_driver_data *data;
> +	struct mtk_drm_private *priv_n;
> +	int i = 0, j;
> +
> +	for (j = 0; j < private->data->mmsys_dev_num; j++) {
> +		priv_n = private->all_drm_private[j];
> +		data = priv_n->data;
> +
> +		if (mtk_ddp_path_available(data->main_path, data->main_len,
> +					   priv_n->comp_node)) {
> +			if (mtk_drm_find_comp_in_ddp(dev, data->main_path,
> +						     data->main_len,
> +						     priv_n->ddp_comp))
> +				return BIT(i);
> +			i++;
> +		}
> +
> +		if (mtk_ddp_path_available(data->ext_path, data->ext_len,
> +					   priv_n->comp_node)) {
> +			if (mtk_drm_find_comp_in_ddp(dev, data->ext_path,
> +						     data->ext_len,
> +						     priv_n->ddp_comp))
> +				return BIT(i);
> +			i++;
> +		}
> +
> +		if (mtk_ddp_path_available(data->third_path, data->third_len,
> +					   priv_n->comp_node)) {
> +			if (mtk_drm_find_comp_in_ddp(dev, data->third_path,
> +						     data->third_len,
> +						     priv_n->ddp_comp))
> +				return BIT(i);
> +			i++;
> +		}
> +	}
> 
> -	return ret;
> +	DRM_INFO("Failed to find comp in ddp table\n");
> +	return -ENOENT;
>  }
> 
>  int mtk_ddp_comp_init(struct device_node *node, struct mtk_ddp_comp 
> *comp,
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h 
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> index febcaeef16a1..6a95df72de0a 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> @@ -277,8 +277,7 @@ static inline bool mtk_ddp_comp_disconnect(struct 
> mtk_ddp_comp *comp, struct dev
> 
>  int mtk_ddp_comp_get_id(struct device_node *node,
>  			enum mtk_ddp_comp_type comp_type);
> -unsigned int mtk_drm_find_possible_crtc_by_comp(struct drm_device 
> *drm,
> -						struct device *dev);
> +int mtk_drm_find_possible_crtc_by_comp(struct drm_device *drm, struct 
> device *dev);
>  int mtk_ddp_comp_init(struct device_node *comp_node, struct 
> mtk_ddp_comp *comp,
>  		      unsigned int comp_id);
>  enum mtk_ddp_comp_type mtk_ddp_comp_get_type(unsigned int comp_id);
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c 
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index d8bfc2cce54d..d67e5c61a9b9 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -843,7 +843,10 @@ static int mtk_dsi_encoder_init(struct drm_device 
> *drm, struct mtk_dsi *dsi)
>  		return ret;
>  	}
> 
> -	dsi->encoder.possible_crtcs = mtk_drm_find_possible_crtc_by_comp(drm, 
> dsi->host.dev);
> +	ret = mtk_drm_find_possible_crtc_by_comp(drm, dsi->host.dev);
> +	if (ret < 0)
> +		goto err_cleanup_encoder;
> +	dsi->encoder.possible_crtcs = ret;
> 
>  	ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
>  				DRM_BRIDGE_ATTACH_NO_CONNECTOR);