linux-kernel - Re: [PATCH 5/5] drm/bridge: simple-bridge: Add next panel support

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Message-ID: <20250304-interesting-solemn-potoo-fd4c6e@houat>
Date: Tue, 4 Mar 2025 11:41:44 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Liu Ying <victor.liu@....com>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch
Subject: Re: [PATCH 5/5] drm/bridge: simple-bridge: Add next panel support

On Tue, Mar 04, 2025 at 06:15:30PM +0800, Liu Ying wrote:
> The next bridge connected to a simple bridge could be a panel, e.g.,
> a DPI panel connected to a DPI color encoder. Add the next panel support,
> instead of supporting non-panel next bridge only.
> 
> Signed-off-by: Liu Ying <victor.liu@....com>
> ---
>  drivers/gpu/drm/bridge/Kconfig         |  1 +
>  drivers/gpu/drm/bridge/simple-bridge.c | 32 ++++++++++++++++----------
>  2 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index d20f1646dac2..92187dbdd32b 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -310,6 +310,7 @@ config DRM_SIMPLE_BRIDGE
>  	tristate "Simple DRM bridge support"
>  	depends on OF
>  	select DRM_KMS_HELPER
> +	select DRM_PANEL_BRIDGE
>  	help
>  	  Support for non-programmable DRM bridges, such as ADI ADV7123, TI
>  	  THS8134 and THS8135 or passive resistor ladder DACs.
> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
> index c0445bd20e07..4c585e5583ca 100644
> --- a/drivers/gpu/drm/bridge/simple-bridge.c
> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
> @@ -19,6 +19,7 @@
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_edid.h>
>  #include <drm/drm_of.h>
> +#include <drm/drm_panel.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
>  
> @@ -35,6 +36,7 @@ struct simple_bridge {
>  	const struct simple_bridge_info *info;
>  
>  	struct drm_bridge	*next_bridge;
> +	struct drm_panel	*next_panel;
>  	struct regulator	*vdd;
>  	struct gpio_desc	*enable;
>  
> @@ -114,6 +116,10 @@ static int simple_bridge_attach(struct drm_bridge *bridge,
>  	struct simple_bridge *sbridge = drm_bridge_to_simple_bridge(bridge);
>  	int ret;
>  
> +	if (sbridge->next_panel)
> +		return drm_bridge_attach(bridge->encoder, sbridge->next_bridge,
> +					 bridge, flags);
> +
>  	ret = drm_bridge_attach(bridge->encoder, sbridge->next_bridge, bridge,
>  				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>  	if (ret < 0)
> @@ -247,7 +253,6 @@ static int simple_bridge_get_dpi_color_coding(struct simple_bridge *sbridge,
>  static int simple_bridge_probe(struct platform_device *pdev)
>  {
>  	struct simple_bridge *sbridge;
> -	struct device_node *remote;
>  	int ret;
>  
>  	sbridge = devm_kzalloc(&pdev->dev, sizeof(*sbridge), GFP_KERNEL);
> @@ -257,17 +262,20 @@ static int simple_bridge_probe(struct platform_device *pdev)
>  	sbridge->info = of_device_get_match_data(&pdev->dev);
>  
>  	/* Get the next bridge in the pipeline. */
> -	remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
> -	if (!remote)
> -		return -EINVAL;
> -
> -	sbridge->next_bridge = of_drm_find_bridge(remote);
> -	of_node_put(remote);
> -
> -	if (!sbridge->next_bridge) {
> -		dev_dbg(&pdev->dev, "Next bridge not found, deferring probe\n");
> -		return -EPROBE_DEFER;
> -	}
> +	ret = drm_of_find_panel_or_bridge(pdev->dev.of_node, 1, -1,
> +					  &sbridge->next_panel,
> +					  &sbridge->next_bridge);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret,
> +				     "Next panel or bridge not found\n");
> +
> +	if (sbridge->next_panel)
> +		sbridge->next_bridge = devm_drm_panel_bridge_add(&pdev->dev,
> +								 sbridge->next_panel);
> +
> +	if (IS_ERR(sbridge->next_bridge))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->next_bridge),
> +				     "Next bridge not found\n");

This makes sense in general, but I think a better approach would be to
use devm/drmm_of_get_bridge here.

Maxime

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