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: Tomi Valkeinen <[email protected]> Link: https://lore.kernel.org/all/[email protected]/ Signed-off-by: Kory Maincent (TI.com) <[email protected]> --- Using the approach of applying an overlay and then modifying the live device tree is the solution I found that requires no modification of the OF core. Dealing entirely with changesets would bring additional requirements such as phandle resolution management, which is internal to the OF framework. I intend to avoid OF core change to support this legacy binding. Change in v4: - Use tab instead of space. Change in v3: - Use __free() macro instead of manual house cleaning. - Enable CONFIG_DRM_TILCDC_PANEL_LEGACY config by default. - Improve config description. - Rename "panel-dpi" to "tilcdc-panel-dpi" to avoid any future conflict. - Use OF changeset instead of modifying the live devicetree step by step. - Add kfree to avoid memory leak. Change in v2: - New patch. --- drivers/gpu/drm/tilcdc/Kconfig | 16 ++ drivers/gpu/drm/tilcdc/Makefile | 2 + drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c | 185 ++++++++++++++++++++++++ drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.dtso | 29 ++++ 4 files changed, 232 insertions(+) diff --git a/drivers/gpu/drm/tilcdc/Kconfig b/drivers/gpu/drm/tilcdc/Kconfig index 24f9a245ba593..a36e809f984cd 100644 --- a/drivers/gpu/drm/tilcdc/Kconfig +++ b/drivers/gpu/drm/tilcdc/Kconfig @@ -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. diff --git a/drivers/gpu/drm/tilcdc/Makefile b/drivers/gpu/drm/tilcdc/Makefile index f5190477de721..6d6a08b5adf40 100644 --- a/drivers/gpu/drm/tilcdc/Makefile +++ b/drivers/gpu/drm/tilcdc/Makefile @@ -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 diff --git a/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c b/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c new file mode 100644 index 0000000000000..37a69b3cf04b2 --- /dev/null +++ b/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.c @@ -0,0 +1,185 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2025 Bootlin + * Author: Kory Maincent <[email protected]> + * + * 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); diff --git a/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.dtso b/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.dtso new file mode 100644 index 0000000000000..ae71d10f5ec13 --- /dev/null +++ b/drivers/gpu/drm/tilcdc/tilcdc_panel_legacy.dtso @@ -0,0 +1,29 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * DTS overlay for converting ti,tilcdc,panel binding to new binding. + * + * Copyright (C) 2025 Bootlin + * Author: Kory Maincent <[email protected]> + */ + +/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>; + }; + }; +}; -- 2.43.0
