Re: [PATCH 2/3] drm/msm/dsi: move next bridge acquisition to dsi_bind

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

On 3/9/2024 7:09 AM, Dmitry Baryshkov wrote:
> Currently the MSM DSI driver looks for the next bridge during
> msm_dsi_modeset_init(). If the bridge is not registered at that point,
> this might result in -EPROBE_DEFER, which can be problematic that late
> during the device probe process. Move next bridge acquisition to the
> dsi_bind state so that probe deferral is returned as early as possible.

But msm_dsi_modeset)init() is also called during msm_drm_bind() only.

What issue are you suggesting will be fixed by moving this from 
msm_drm_bind() to dsi_bind()?

> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> ---
>   drivers/gpu/drm/msm/dsi/dsi.c         | 16 ++++++++++++++++
>   drivers/gpu/drm/msm/dsi/dsi.h         |  2 ++
>   drivers/gpu/drm/msm/dsi/dsi_manager.c |  8 +-------
>   3 files changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
> index 37c4c07005fe..38f10f7a10d3 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi.c
> @@ -120,6 +120,22 @@ static int dsi_bind(struct device *dev, struct device *master, void *data)
>   	struct msm_drm_private *priv = dev_get_drvdata(master);
>   	struct msm_dsi *msm_dsi = dev_get_drvdata(dev);
>   
> +	/*
> +	 * Next bridge doesn't exist for the secondary DSI host in a bonded
> +	 * pair.
> +	 */
> +	if (!msm_dsi_is_bonded_dsi(msm_dsi) ||
> +	    msm_dsi_is_master_dsi(msm_dsi)) {
> +		struct drm_bridge *ext_bridge;
> +
> +		ext_bridge = devm_drm_of_get_bridge(&msm_dsi->pdev->dev,
> +						    msm_dsi->pdev->dev.of_node, 1, 0);
> +		if (IS_ERR(ext_bridge))
> +			return PTR_ERR(ext_bridge);
> +
> +		msm_dsi->next_bridge = ext_bridge;
> +	}
> +
>   	priv->dsi[msm_dsi->id] = msm_dsi;
>   
>   	return 0;
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
> index 2ad9a842c678..0adef65be1de 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.h
> +++ b/drivers/gpu/drm/msm/dsi/dsi.h
> @@ -38,6 +38,8 @@ struct msm_dsi {
>   	struct mipi_dsi_host *host;
>   	struct msm_dsi_phy *phy;
>   
> +	struct drm_bridge *next_bridge;
> +
>   	struct device *phy_dev;
>   	bool phy_enabled;
>   
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index a7c7f85b73e4..b7c52b14c790 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -464,18 +464,12 @@ int msm_dsi_manager_ext_bridge_init(u8 id, struct drm_bridge *int_bridge)
>   	struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
>   	struct drm_device *dev = msm_dsi->dev;
>   	struct drm_encoder *encoder;
> -	struct drm_bridge *ext_bridge;
>   	struct drm_connector *connector;
>   	int ret;
>   
> -	ext_bridge = devm_drm_of_get_bridge(&msm_dsi->pdev->dev,
> -					    msm_dsi->pdev->dev.of_node, 1, 0);
> -	if (IS_ERR(ext_bridge))
> -		return PTR_ERR(ext_bridge);
> -
>   	encoder = int_bridge->encoder;
>   
> -	ret = drm_bridge_attach(encoder, ext_bridge, int_bridge,
> +	ret = drm_bridge_attach(encoder, msm_dsi->next_bridge, int_bridge,
>   			DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>   	if (ret)
>   		return ret;