Commit 0ff223d9 authored by Kory Maincent (TI.com)'s avatar Kory Maincent (TI.com) Committed by Luca Ceresoli
Browse files

drm/tilcdc: Convert legacy panel binding via DT overlay at boot time 



To maintain backward compatibility while removing the deprecated
tilcdc_panel driver, add a tilcdc_panel_legacy subdriver that converts
the legacy "ti,tilcdc,panel" devicetree binding to the standard
panel-dpi binding at early boot.

The conversion uses an embedded device tree overlay that is applied and
modified during subsys_initcall. The process:

- Apply embedded overlay to create a tilcdc-panel-dpi node with
  port/endpoint connections to the LCDC
- Copy all properties from the legacy panel node to the new
  tilcdc-panel-dpi node
- Copy display-timings from the legacy panel
- Convert legacy panel-info properties (invert-pxl-clk, sync-edge) to
  standard display timing properties (pixelclk-active, syncclk-active)
- Disable the legacy panel by removing its compatible property to
  prevent the deprecated driver from binding

The result is a standard tilcdc-panel-dpi node with proper endpoints and
timing properties, allowing the DRM panel infrastructure to work with
legacy devicetrees without modification.

Other legacy panel-info properties are not migrated as they consistently
use default values across all mainline devicetrees and can be hardcoded
in the tilcdc driver.

This feature is optional via CONFIG_DRM_TILCDC_PANEL_LEGACY and should
only be enabled for systems with legacy devicetrees containing
"ti,tilcdc,panel" nodes.

Suggested-by: default avatarTomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://lore.kernel.org/all/1d9a9269-bfda-4d43-938b-2df6b82b9369@ideasonboard.com/


Reviewed-by: default avatarLuca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: default avatarHerve Codina <herve.codina@bootlin.com>
Signed-off-by: default avatarKory Maincent (TI.com) <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20260123-feature_tilcdc-v5-5-5a44d2aa3f6f@bootlin.com


Signed-off-by: default avatarLuca Ceresoli <luca.ceresoli@bootlin.com>
parent ca062af4

drivers/gpu/drm/tilcdc/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -14,3 +14,19 @@ config DRM_TILCDC 
	  controller, for example AM33xx in beagle-bone, DA8xx, or

	  OMAP-L1xx.  This driver replaces the FB_DA8XX fbdev driver.



config DRM_TILCDC_PANEL_LEGACY

	bool "Support device tree blobs using TI LCDC Panel binding"

	default y

	depends on DRM_TILCDC

	depends on OF

	depends on BACKLIGHT_CLASS_DEVICE

	depends on PM

	select OF_OVERLAY

	select DRM_PANEL_SIMPLE

	help

	  Modifies the live device tree at early boot to convert the legacy

	  "ti,tilcdc,panel" devicetree node to the standard panel-dpi node.

	  This allows to maintain backward compatibility for boards which

	  were using the deprecated tilcdc_panel driver.

	  If you find "ti,tilcdc,panel"-string from your DTB, you probably

	  need this. Otherwise you do not.

drivers/gpu/drm/tilcdc/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -11,3 +11,5 @@ tilcdc-y := \ 
	tilcdc_drv.o



obj-$(CONFIG_DRM_TILCDC)	+= tilcdc.o

obj-$(CONFIG_DRM_TILCDC_PANEL_LEGACY)	+= tilcdc_panel_legacy.o \

					   tilcdc_panel_legacy.dtbo.o

drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c

0 → 100644
+185 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Copyright (C) 2025 Bootlin

 * Author: Kory Maincent <kory.maincent@bootlin.com>

 *

 * To support the legacy "ti,tilcdc,panel" binding, the devicetree has to

 * be transformed to the new panel-dpi binding with the endpoint associated.

 */



#include <linux/kernel.h>

#include <linux/of.h>

#include <linux/of_fdt.h>

#include <linux/slab.h>



/* Embedded dtbo symbols created by cmd_wrap_S_dtb in scripts/Makefile.lib */

extern char __dtbo_tilcdc_panel_legacy_begin[];

extern char __dtbo_tilcdc_panel_legacy_end[];



static int __init

tilcdc_panel_update_prop(struct of_changeset *ocs, struct device_node *node,

			 char *name, void *val, int length)

{

	struct property *prop;



	prop = kzalloc(sizeof(*prop), GFP_KERNEL);

	if (!prop)

		return -ENOMEM;



	prop->name = kstrdup(name, GFP_KERNEL);

	prop->length = length;

	prop->value = kmemdup(val, length, GFP_KERNEL);

	if (!prop->name || !prop->value) {

		kfree(prop->name);

		kfree(prop->value);

		kfree(prop);

		return -ENOMEM;

	}



	return of_changeset_update_property(ocs, node, prop);

}



static int __init tilcdc_panel_copy_props(struct device_node *old_panel,

					  struct device_node *new_panel)

{

	struct device_node *old_timing __free(device_node) = NULL;

	struct device_node *new_timing __free(device_node) = NULL;

	struct device_node *panel_info __free(device_node) = NULL;

	struct device_node *child __free(device_node) = NULL;

	u32 invert_pxl_clk = 0, sync_edge = 0;

	struct of_changeset ocs;

	struct property *prop;

	int ret;



	child = of_get_child_by_name(old_panel, "display-timings");

	if (!child)

		return -EINVAL;



	/* The default display timing is the one specified as native-mode.

	 * If no native-mode is specified then the first node is assumed

	 * to be the native mode.

	 */

	old_timing = of_parse_phandle(child, "native-mode", 0);

	if (!old_timing) {

		old_timing = of_get_next_child(child, NULL);

		if (!old_timing)

			return -EINVAL;

	}



	panel_info = of_get_child_by_name(old_panel, "panel-info");

	if (!panel_info)

		return -EINVAL;



	of_changeset_init(&ocs);



	/* Copy all panel properties to the new panel node */

	for_each_property_of_node(old_panel, prop) {

		if (!strncmp(prop->name, "compatible", sizeof("compatible")))

			continue;



		ret = tilcdc_panel_update_prop(&ocs, new_panel, prop->name,

					       prop->value, prop->length);

		if (ret)

			goto destroy_ocs;

	}



	new_timing = of_changeset_create_node(&ocs, new_panel, "panel-timing");

	if (!new_timing) {

		ret = -ENODEV;

		goto destroy_ocs;

	}



	/* Copy all panel timing properties to the new panel node */

	for_each_property_of_node(old_timing, prop) {

		ret = tilcdc_panel_update_prop(&ocs, new_timing, prop->name,

					       prop->value, prop->length);

		if (ret)

			goto destroy_ocs;

	}



	/* Looked only for these two parameter as all the other are always

	 * set to default and not related to common DRM properties.

	 */

	of_property_read_u32(panel_info, "invert-pxl-clk", &invert_pxl_clk);

	of_property_read_u32(panel_info, "sync-edge", &sync_edge);



	if (!invert_pxl_clk) {

		ret = tilcdc_panel_update_prop(&ocs, new_timing, "pixelclk-active",

					       &(u32){cpu_to_be32(1)}, sizeof(u32));

		if (ret)

			goto destroy_ocs;

	}



	if (!sync_edge) {

		ret = tilcdc_panel_update_prop(&ocs, new_timing, "syncclk-active",

					       &(u32){cpu_to_be32(1)}, sizeof(u32));

		if (ret)

			goto destroy_ocs;

	}



	/* Remove compatible property to avoid any driver compatible match */

	of_changeset_remove_property(&ocs, old_panel,

				     of_find_property(old_panel, "compatible", NULL));



	of_changeset_apply(&ocs);

	return 0;



destroy_ocs:

	of_changeset_destroy(&ocs);

	return ret;

}



static const struct of_device_id tilcdc_panel_of_match[] __initconst = {

	{ .compatible = "ti,tilcdc,panel", },

	{},

};



static const struct of_device_id tilcdc_of_match[] __initconst = {

	{ .compatible = "ti,am33xx-tilcdc", },

	{ .compatible = "ti,da850-tilcdc", },

	{},

};



static int __init tilcdc_panel_legacy_init(void)

{

	struct device_node *new_panel __free(device_node) = NULL;

	struct device_node *panel __free(device_node) = NULL;

	struct device_node *lcdc __free(device_node) = NULL;

	void *dtbo_start;

	u32 dtbo_size;

	int ovcs_id;

	int ret;



	lcdc = of_find_matching_node(NULL, tilcdc_of_match);

	panel = of_find_matching_node(NULL, tilcdc_panel_of_match);



	if (!of_device_is_available(panel) ||

	    !of_device_is_available(lcdc))

		return 0;



	dtbo_start = __dtbo_tilcdc_panel_legacy_begin;

	dtbo_size = __dtbo_tilcdc_panel_legacy_end -

		    __dtbo_tilcdc_panel_legacy_begin;



	ret = of_overlay_fdt_apply(dtbo_start, dtbo_size, &ovcs_id, NULL);

	if (ret)

		return ret;



	new_panel = of_find_node_by_name(NULL, "tilcdc-panel-dpi");

	if (!new_panel) {

		ret = -ENODEV;

		goto overlay_remove;

	}



	ret = tilcdc_panel_copy_props(panel, new_panel);

	if (ret)

		goto overlay_remove;



	return 0;



overlay_remove:

	of_overlay_remove(&ovcs_id);

	return ret;

}



subsys_initcall(tilcdc_panel_legacy_init);

drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.dtso

0 → 100644
+29 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0+

/*

 * DTS overlay for converting ti,tilcdc,panel binding to new binding.

 *

 * Copyright (C) 2025 Bootlin

 * Author: Kory Maincent <kory.maincent@bootlin.com>

 */



/dts-v1/;

/plugin/;



&{/} {

	tilcdc-panel-dpi {

		compatible = "panel-dpi";

		port {

			panel_in: endpoint@0 {

				remote-endpoint = <&lcd_0>;

			};

		};

	};

};



&lcdc {

	port {

		lcd_0: endpoint@0 {

			remote-endpoint = <&panel_in>;

		};

	};

};