Re: [linux-sunxi] [PATCH 3/6] drm/sun4i: dsi: Add bridge support

[Paul Kocialkowski]

Hi,

On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
> Some display panels would come up with a non-DSI output which
> can have an option to connect DSI interface by means of bridge
> convertor.
> 
> This DSI to non-DSI bridge convertor would require a bridge
> driver that would communicate the DSI controller for bridge
> functionalities.
> 
> So, add support for bridge functionalities in Allwinner DSI
> controller.

See a few comments below.

> Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
>  2 files changed, 49 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 0960b96b62cc..64d74313b842 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel))
>  		drm_panel_prepare(dsi->panel);
>  
> +	if (!IS_ERR(dsi->bridge))
> +		drm_bridge_pre_enable(dsi->bridge);
> +
>  	/*
>  	 * FIXME: This should be moved after the switch to HS mode.
>  	 *
> @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel))
>  		drm_panel_enable(dsi->panel);
>  
> +	if (!IS_ERR(dsi->bridge))
> +		drm_bridge_enable(dsi->bridge);
> +
>  	sun6i_dsi_start(dsi, DSI_START_HSC);
>  
>  	udelay(1000);
> @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel)) {
>  		drm_panel_disable(dsi->panel);
>  		drm_panel_unprepare(dsi->panel);
> +	} else if (!IS_ERR(dsi->bridge)) {
> +		drm_bridge_disable(dsi->bridge);
> +		drm_bridge_post_disable(dsi->bridge);
>  	}
>  
>  	phy_power_off(dsi->dphy);
> @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
>  	struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
>  
>  	dsi->device = device;
> -	dsi->panel = of_drm_find_panel(device->dev.of_node);
> -	if (IS_ERR(dsi->panel))
> -		return PTR_ERR(dsi->panel);
>  
> -	dev_info(host->dev, "Attached device %s\n", device->name);
> +	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> +	if (!dsi->bridge) {

You are using IS_ERR to check that the bridge is alive in the changes
above, but switch to checking that it's non-NULL at this point.

Are both guaranteed to be interchangeable?

> +		dsi->panel = of_drm_find_panel(device->dev.of_node);
> +		if (IS_ERR(dsi->panel))
> +			return PTR_ERR(dsi->panel);
> +	}

You should probably use drm_of_find_panel_or_bridge instead of
duplicating the logic here.

> +	dev_info(host->dev, "Attached %s %s\n",
> +		 dsi->bridge ? "bridge" : "panel", device->name);
>  
>  	return 0;
>  }
> @@ -1055,8 +1069,10 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
>  	struct sun4i_tcon *tcon0 = sun4i_get_tcon0(drm);
>  	int ret;
>  
> -	if (!dsi->panel)
> +	if (!(dsi->panel || dsi->bridge)) {
> +		dev_info(drm->dev, "No panel or bridge found... DSI output disabled\n");
>  		return -EPROBE_DEFER;
> +	}
>  
>  	dsi->drv = drv;
>  
> @@ -1078,19 +1094,29 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
>  	}
>  	dsi->encoder.possible_crtcs = BIT(0);
>  
> -	drm_connector_helper_add(&dsi->connector,
> -				 &sun6i_dsi_connector_helper_funcs);
> -	ret = drm_connector_init(drm, &dsi->connector,
> -				 &sun6i_dsi_connector_funcs,
> -				 DRM_MODE_CONNECTOR_DSI);
> -	if (ret) {
> -		dev_err(dsi->dev,
> -			"Couldn't initialise the DSI connector\n");
> -		goto err_cleanup_connector;
> +	if (dsi->panel) {
> +		drm_connector_helper_add(&dsi->connector,
> +					 &sun6i_dsi_connector_helper_funcs);
> +		ret = drm_connector_init(drm, &dsi->connector,
> +					 &sun6i_dsi_connector_funcs,
> +					 DRM_MODE_CONNECTOR_DSI);
> +		if (ret) {
> +			dev_err(dsi->dev,
> +				"Couldn't initialise the DSI connector\n");
> +			goto err_cleanup_connector;
> +		}
> +
> +		drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> +		drm_panel_attach(dsi->panel, &dsi->connector);
>  	}
>  
> -	drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> -	drm_panel_attach(dsi->panel, &dsi->connector);
> +	if (dsi->bridge) {
> +		ret = drm_bridge_attach(&dsi->encoder, dsi->bridge, NULL);
> +		if (ret) {
> +			dev_err(dsi->dev, "Couldn't attach the DSI bridge\n");
> +			goto err_cleanup_connector;
> +		}
> +	}
>  
>  	return 0;
>  
> @@ -1104,7 +1130,12 @@ static void sun6i_dsi_unbind(struct device *dev, struct device *master,
>  {
>  	struct sun6i_dsi *dsi = dev_get_drvdata(dev);
>  
> -	drm_panel_detach(dsi->panel);
> +	if (dsi->panel)
> +		drm_panel_detach(dsi->panel);
> +
> +	if (dsi->bridge)
> +		drm_bridge_detach(dsi->bridge);

As I mentionned in the first patch, this is quite suspicious since the
DRM core should be in charge of detaching the bridge, not the driver.

Cheers,

Paul

> +
>  }
>  
>  static const struct component_ops sun6i_dsi_ops = {
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> index 5c4983212f89..76874ff8e3ef 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> @@ -36,6 +36,7 @@ struct sun6i_dsi {
>  	struct sun4i_tcon	*tcon;
>  	struct mipi_dsi_device	*device;
>  	struct drm_panel	*panel;
> +	struct drm_bridge	*bridge;
>  	const struct sun6i_dsi_variant	*variant;
>  };
>  
> -- 
> 2.18.0.321.gffc6fa0e3
> 
-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com