[PATCH 1/3] arm: mediatek: add RITY devicetree preparation

RITY images select a base devicetree and an ordered list of overlays
through the storage, storage_dev, dtb_path, boot_dtb, fdtfile and list_dtbo
environment variables. The selected tree must be assembled before EFI
boot and published through the standard fdt_addr variable.

Add a MediaTek preparation service which consumes that established
interface. For block devices, locate the source partition by the existing
MediaTek GPT type GUID. Also support the RITY NOR layout through MTD, UBI
and UBIFS when those subsystems are enabled.

Load the base tree and apply the overlays in list order.
Non-authenticated builds consume raw DTB and DTBO files. With MTK_FDT_AUTH
enabled, treat each same-named file as a single-image FIT, verify its
flat-devicetree payload and extract it before using the common assembly
path.

Publish the result through fdt_addr only after the whole tree has been
prepared successfully. Clear fdt_addr on failure and remove fdtfile from
the EFI fallback search so a preparation failure cannot silently fall back
to a different tree.

Run the service at EVT_POST_PREBOOT for EFI-capable boot targets, while
leaving embedded legacy boot unchanged. Provide a separately selectable
mtk_fdt_prepare command so an interactive user can rebuild the tree after
changing a selector. It accepts either no arguments, using the environment,
or explicit interface, device and directory arguments.

Signed-off-by: Carlo Caione <[email protected]>
---
 arch/arm/mach-mediatek/Kconfig           |  35 +++
 arch/arm/mach-mediatek/Makefile          |   2 +
 arch/arm/mach-mediatek/cmd_fdt_prepare.c |  31 ++
 arch/arm/mach-mediatek/fdt_prepare.c     | 502 +++++++++++++++++++++++++++++++
 arch/arm/mach-mediatek/fdt_prepare.h     |  10 +
 5 files changed, 580 insertions(+)

diff --git a/arch/arm/mach-mediatek/Kconfig b/arch/arm/mach-mediatek/Kconfig
index 5e6c50ca64d..75fa88a1510 100644
--- a/arch/arm/mach-mediatek/Kconfig
+++ b/arch/arm/mach-mediatek/Kconfig
@@ -215,4 +215,39 @@ config MTK_TZ_MOVABLE
 	select OF_SYSTEM_SETUP
 	bool
 
+config MTK_FDT_PREPARE
+	bool "Prepare a MediaTek RITY devicetree"
+	select EVENT
+	select PARTITION_TYPE_GUID
+	depends on OF_LIBFDT_OVERLAY
+	help
+	  Load the base devicetree and the overlays selected by list_dtbo,
+	  assemble them before autoboot and publish the resulting tree through
+	  the standard fdt_addr environment variable.
+
+	  The source and selection are described by the RITY environment
+	  variables storage, storage_dev, dtb_path, boot_dtb, fdtfile and
+	  list_dtbo. Both block filesystems and, when enabled, UBI/UBIFS
+	  storage are supported.
+
+config CMD_MTK_FDT_PREPARE
+	bool "Enable the 'mtk_fdt_prepare' command"
+	depends on MTK_FDT_PREPARE
+	help
+	  Provide the mtk_fdt_prepare command so the assembled devicetree can
+	  be rebuilt after changing a selector at the U-Boot prompt. With no
+	  arguments the command uses storage, storage_dev and dtb_path from the
+	  environment. It also accepts the interface, device and path arguments
+	  explicitly.
+
+config MTK_FDT_AUTH
+	bool "Authenticate MediaTek RITY devicetrees"
+	depends on MTK_FDT_PREPARE && FIT_SIGNATURE
+	select RSA
+	select RSA_VERIFY
+	help
+	  Treat every loose-named DTB and DTBO as a signed single-image FIT,
+	  authenticate its default flat-devicetree image and extract the
+	  verified payload before assembling the final tree.
+
 endif
diff --git a/arch/arm/mach-mediatek/Makefile b/arch/arm/mach-mediatek/Makefile
index 35f748a70d6..e11fddd27bc 100644
--- a/arch/arm/mach-mediatek/Makefile
+++ b/arch/arm/mach-mediatek/Makefile
@@ -3,6 +3,8 @@
 obj-$(CONFIG_ARM64) += armv8-mem-map.o
 obj-y	+= cpu.o
 obj-$(CONFIG_MTK_TZ_MOVABLE)	+= tzcfg.o
+obj-$(CONFIG_MTK_FDT_PREPARE)	+= fdt_prepare.o
+obj-$(CONFIG_CMD_MTK_FDT_PREPARE)	+= cmd_fdt_prepare.o
 obj-$(CONFIG_XPL_BUILD)	+= spl.o
 
 obj-$(CONFIG_TARGET_MT7622) += mt7622/
diff --git a/arch/arm/mach-mediatek/cmd_fdt_prepare.c b/arch/arm/mach-mediatek/cmd_fdt_prepare.c
new file mode 100644
index 00000000000..91d56f747ef
--- /dev/null
+++ b/arch/arm/mach-mediatek/cmd_fdt_prepare.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2026 Carlo Caione <[email protected]>
+ */
+
+#include <command.h>
+
+#include "fdt_prepare.h"
+
+static int do_mtk_fdt_prepare(struct cmd_tbl *cmdtp, int flag, int argc,
+			      char *const argv[])
+{
+	int ret;
+
+	if (argc == 1)
+		ret = mtk_fdt_prepare();
+	else if (argc == 4)
+		ret = mtk_fdt_prepare_from(argv[1], argv[2], argv[3]);
+	else
+		return CMD_RET_USAGE;
+
+	return ret ? CMD_RET_FAILURE : CMD_RET_SUCCESS;
+}
+
+#define MTK_FDT_PREPARE_USAGE \
+	"[<interface> <dev> <probe_base>]\n" \
+	"    - use the environment when no source arguments are given"
+
+U_BOOT_CMD(mtk_fdt_prepare, 4, 1, do_mtk_fdt_prepare,
+	   "load and assemble the MediaTek RITY devicetree",
+	   MTK_FDT_PREPARE_USAGE);
diff --git a/arch/arm/mach-mediatek/fdt_prepare.c b/arch/arm/mach-mediatek/fdt_prepare.c
new file mode 100644
index 00000000000..ff5e1e02820
--- /dev/null
+++ b/arch/arm/mach-mediatek/fdt_prepare.c
@@ -0,0 +1,502 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2026 Carlo Caione <[email protected]>
+ */
+
+#include <blk.h>
+#include <env.h>
+#include <event.h>
+#include <fdt_support.h>
+#include <fs.h>
+#include <image.h>
+#include <log.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <part.h>
+#include <vsprintf.h>
+#include <linux/errno.h>
+#include <linux/libfdt.h>
+#include <linux/string.h>
+
+#include "fdt_prepare.h"
+
+#if CONFIG_IS_ENABLED(MTD) && CONFIG_IS_ENABLED(CMD_UBI) && \
+	CONFIG_IS_ENABLED(CMD_UBIFS)
+#include <mtd.h>
+#include <ubi_uboot.h>
+#include <ubifs_uboot.h>
+#define MTK_FDT_HAS_UBI 1
+#else
+#define MTK_FDT_HAS_UBI 0
+#endif
+
+#define MTK_FW_PART_GUID	"384e979b-eb76-435a-a3a6-1a071dbad91d"
+#define MTK_FDT_PATH_MAX	512
+
+enum mtk_fdt_source_type {
+	MTK_FDT_SOURCE_BLOCK,
+	MTK_FDT_SOURCE_UBI,
+};
+
+struct mtk_fdt_source {
+	enum mtk_fdt_source_type type;
+	struct blk_desc *desc;
+	int part;
+};
+
+static int mtk_fdt_make_path(char *path, size_t size, const char *dir,
+			     const char *name)
+{
+	int len;
+
+	if (!dir || !*dir || !name || !*name)
+		return -EINVAL;
+
+	len = snprintf(path, size, "%s%s%s", dir,
+		       dir[strlen(dir) - 1] == '/' ? "" : "/", name);
+	if (len < 0 || (size_t)len >= size)
+		return -ENOSPC;
+
+	return 0;
+}
+
+static int mtk_fdt_block_read(struct mtk_fdt_source *source,
+			      const char *path, ulong addr, loff_t *sizep)
+{
+	int ret;
+
+	ret = fs_set_blk_dev_with_part(source->desc, source->part);
+	if (ret)
+		return ret;
+
+	return fs_read(path, addr, 0, 0, sizep);
+}
+
+static int mtk_fdt_block_exists(struct blk_desc *desc, int part,
+				const char *path)
+{
+	int ret;
+
+	ret = fs_set_blk_dev_with_part(desc, part);
+	if (ret)
+		return ret;
+
+	return fs_exists(path) ? 0 : -ENOENT;
+}
+
+static int mtk_fdt_select_block(struct mtk_fdt_source *source,
+				const char *path, const char *ifname,
+				const char *devnum)
+{
+	const char *boot_dtb = env_get("boot_dtb");
+	const char *type_guid = env_get("fw_fdt_part_type_uuid");
+	struct disk_partition info;
+	struct blk_desc *desc;
+	ulong selected = 0;
+	int part, ret;
+
+	if (!ifname || !devnum)
+		return -EINVAL;
+	if (!type_guid || !*type_guid)
+		type_guid = MTK_FW_PART_GUID;
+
+	if (boot_dtb && *boot_dtb &&
+	    strict_strtoul(boot_dtb, 10, &selected)) {
+		printf("Invalid boot_dtb partition number: %s\n", boot_dtb);
+		return -EINVAL;
+	}
+
+	ret = blk_get_device_by_str(ifname, devnum, &desc);
+	if (ret < 0)
+		return ret;
+
+	for (part = 1; part <= MAX_SEARCH_PARTITIONS; part++) {
+		ret = part_get_info(desc, part, &info);
+		if (ret)
+			continue;
+		if (strcasecmp(info.type_guid, type_guid))
+			continue;
+		if (selected && selected != part)
+			continue;
+
+		printf("Probing %s %s:%d for RITY devicetree...\n",
+		       ifname, devnum, part);
+		ret = mtk_fdt_block_exists(desc, part, path);
+		if (ret)
+			continue;
+
+		source->type = MTK_FDT_SOURCE_BLOCK;
+		source->desc = desc;
+		source->part = part;
+		return 0;
+	}
+
+	return -ENOENT;
+}
+
+#if MTK_FDT_HAS_UBI
+static int mtk_fdt_ubi_read(const char *path, ulong addr, loff_t *sizep)
+{
+	int ret;
+
+	ret = ubifs_load(path, addr, 0);
+	if (!ret)
+		*sizep = env_get_hex("filesize", 0);
+
+	return ret;
+}
+
+static int mtk_fdt_try_ubi_source(struct mtk_fdt_source *source,
+				  const struct mtd_info *mtd,
+				  const char *devnum, const char *path)
+{
+	char volume[UBI_VOL_NAME_MAX + 16];
+	int ret;
+
+	ret = ubi_part(mtd->name, NULL);
+	if (ret)
+		return ret;
+
+	ret = snprintf(volume, sizeof(volume), "ubi%s:%s", devnum, mtd->name);
+	if (ret < 0 || (size_t)ret >= sizeof(volume))
+		return -ENOSPC;
+
+	ret = cmd_ubifs_mount(volume);
+	if (ret)
+		return ret;
+	if (!ubifs_exists(path))
+		return -ENOENT;
+
+	source->type = MTK_FDT_SOURCE_UBI;
+	return 0;
+}
+
+static int mtk_fdt_select_ubi(struct mtk_fdt_source *source,
+			      const char *path, const char *devnum)
+{
+	const char *boot_dtb = env_get("boot_dtb");
+	const char *match = env_get("fw_fdt_mtd_name");
+	struct mtd_info *mtd;
+	ulong selected = 0;
+	int ret;
+
+	if (!devnum)
+		return -EINVAL;
+	if (!match || !*match)
+		match = "firmware";
+
+	if (boot_dtb && *boot_dtb &&
+	    strict_strtoul(boot_dtb, 10, &selected)) {
+		printf("Invalid boot_dtb MTD index: %s\n", boot_dtb);
+		return -EINVAL;
+	}
+
+	ret = mtd_probe_devices();
+	if (ret)
+		return ret;
+
+	mtd_for_each_device(mtd) {
+		if (!mtd_is_partition(mtd) || !mtd->name)
+			continue;
+		if (!strstr(mtd->name, match))
+			continue;
+		if (selected && selected != mtd->index)
+			continue;
+
+		printf("Probing UBI source %s for RITY devicetree...\n",
+		       mtd->name);
+		ret = mtk_fdt_try_ubi_source(source, mtd, devnum, path);
+		if (!ret)
+			return 0;
+	}
+
+	return -ENOENT;
+}
+#else
+static int mtk_fdt_select_ubi(struct mtk_fdt_source *source,
+			      const char *path, const char *devnum)
+{
+	printf("MediaTek RITY devicetree UBI support is not enabled\n");
+	return -ENOSYS;
+}
+#endif
+
+static int mtk_fdt_select_source(struct mtk_fdt_source *source,
+				 const char *path, const char *storage,
+				 const char *storage_dev)
+{
+	if (!storage || !storage_dev)
+		return -EINVAL;
+	if (!strcmp(storage, "ubi"))
+		return mtk_fdt_select_ubi(source, path, storage_dev);
+
+	return mtk_fdt_select_block(source, path, storage, storage_dev);
+}
+
+static int mtk_fdt_source_read(struct mtk_fdt_source *source,
+			       const char *path, ulong addr, loff_t *sizep)
+{
+	if (source->type == MTK_FDT_SOURCE_BLOCK)
+		return mtk_fdt_block_read(source, path, addr, sizep);
+
+#if MTK_FDT_HAS_UBI
+	return mtk_fdt_ubi_read(path, addr, sizep);
+#else
+	return -ENOSYS;
+#endif
+}
+
+#if CONFIG_IS_ENABLED(MTK_FDT_AUTH)
+static int mtk_fdt_extract_verified(ulong fit_addr, loff_t fit_size,
+				    ulong dest_addr, size_t *sizep)
+{
+	const void *fit_data;
+	const char *uname;
+	void *dest, *fit;
+	size_t fit_len;
+	int images, node, ret;
+
+	fit = map_sysmem(fit_addr, fit_size);
+	ret = fit_check_format(fit, fit_size);
+	if (ret)
+		goto out;
+
+	images = fdt_path_offset(fit, FIT_IMAGES_PATH);
+	if (images < 0) {
+		ret = images;
+		goto out;
+	}
+
+	uname = fdt_getprop(fit, images, FIT_DEFAULT_PROP, NULL);
+	if (!uname) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	node = fit_image_get_node(fit, uname);
+	if (node < 0) {
+		ret = node;
+		goto out;
+	}
+	if (!fit_image_check_type(fit, node, IH_TYPE_FLATDT)) {
+		ret = -ENOEXEC;
+		goto out;
+	}
+	if (!fit_image_verify(fit, node)) {
+		ret = -EACCES;
+		goto out;
+	}
+
+	ret = fit_image_get_data(fit, node, &fit_data, &fit_len);
+	if (ret)
+		goto out;
+
+	dest = map_sysmem(dest_addr, fit_len);
+	memmove(dest, fit_data, fit_len);
+	unmap_sysmem(dest);
+	*sizep = fit_len;
+out:
+	unmap_sysmem(fit);
+	return ret;
+}
+#endif
+
+static int mtk_fdt_load(struct mtk_fdt_source *source, const char *path,
+			ulong dest_addr, size_t *sizep)
+{
+	loff_t size;
+	ulong load_addr = dest_addr;
+	int ret;
+
+#if CONFIG_IS_ENABLED(MTK_FDT_AUTH)
+	load_addr = env_get_hex("fw_fdt_wrapper_addr_r", 0);
+	if (!load_addr) {
+		printf("fw_fdt_wrapper_addr_r is not set\n");
+		return -EINVAL;
+	}
+#endif
+
+	printf("Loading RITY devicetree '%s'\n", path);
+	ret = mtk_fdt_source_read(source, path, load_addr, &size);
+	if (ret)
+		return ret;
+	if (!size)
+		return -EINVAL;
+
+#if CONFIG_IS_ENABLED(MTK_FDT_AUTH)
+	ret = mtk_fdt_extract_verified(load_addr, size, dest_addr, sizep);
+	if (ret) {
+		printf("Authentication failed for '%s' (%d)\n", path, ret);
+		return -EKEYREJECTED;
+	}
+
+	return 0;
+#else
+	*sizep = size;
+	return 0;
+#endif
+}
+
+static int mtk_fdt_apply_overlays(struct mtk_fdt_source *source,
+				  void *working_fdt, const char *dtb_path)
+{
+	const char *list = env_get("list_dtbo");
+	ulong overlay_addr = env_get_hex("fdtoverlay_addr_r", 0);
+	char path[MTK_FDT_PATH_MAX];
+	char *copy, *overlay, *next;
+	size_t size;
+	void *blob;
+	int ret = 0;
+
+	if (!list || !*list)
+		return 0;
+	if (!overlay_addr)
+		return -EINVAL;
+
+	copy = strdup(list);
+	if (!copy)
+		return -ENOMEM;
+	next = copy;
+
+	while ((overlay = strsep(&next, " "))) {
+		if (!*overlay)
+			continue;
+
+		ret = mtk_fdt_make_path(path, sizeof(path), dtb_path, overlay);
+		if (ret)
+			break;
+		ret = mtk_fdt_load(source, path, overlay_addr, &size);
+		if (ret)
+			break;
+
+		blob = map_sysmem(overlay_addr, size);
+		ret = fdt_check_header(blob);
+		if (!ret)
+			ret = fdt_overlay_apply_verbose(working_fdt, blob);
+		unmap_sysmem(blob);
+		if (ret)
+			break;
+	}
+
+	free(copy);
+	return ret;
+}
+
+int mtk_fdt_prepare_from(const char *storage, const char *storage_dev,
+			 const char *dtb_path)
+{
+	const char *fdtfile = env_get("fdtfile");
+	struct mtk_fdt_source source = {};
+	ulong fdt_addr = env_get_hex("fdt_addr_r", 0);
+	ulong fdt_resize = env_get_hex("fdt_resize", 0);
+	char path[MTK_FDT_PATH_MAX];
+	void *working_fdt;
+	size_t size;
+	int ret;
+
+	/*
+	 * Never leave a previous or fallback tree published after an error.
+	 * Publish zero rather than deleting fdt_addr: efi_install_fdt() falls
+	 * back to fdtcontroladdr when fdt_addr is absent, while a zero value
+	 * shadows that fallback and is rejected, so a failed preparation
+	 * cannot boot an OS with the U-Boot control devicetree.
+	 */
+	env_set_hex("fdt_addr", 0);
+	env_set_hex("fw_fdt_size", 0);
+
+	if (fdtfile && *fdtfile) {
+		ret = env_set("fw_fdtfile", fdtfile);
+		if (ret)
+			return ret;
+	}
+	env_set("fdtfile", NULL);
+	fdtfile = env_get("fw_fdtfile");
+
+	if (!fdt_addr || !dtb_path || !fdtfile || !*fdtfile)
+		return -EINVAL;
+
+	ret = mtk_fdt_make_path(path, sizeof(path), dtb_path, fdtfile);
+	if (ret)
+		return ret;
+	ret = mtk_fdt_select_source(&source, path, storage, storage_dev);
+	if (ret) {
+		printf("No RITY devicetree source contains '%s'\n", path);
+		return ret;
+	}
+
+	ret = mtk_fdt_load(&source, path, fdt_addr, &size);
+	if (ret)
+		return ret;
+
+	working_fdt = map_sysmem(fdt_addr, size);
+	ret = fdt_check_header(working_fdt);
+	if (ret)
+		goto out;
+
+	ret = fdt_shrink_to_minimum(working_fdt, fdt_resize);
+	if (ret < 0)
+		goto out;
+
+	ret = mtk_fdt_apply_overlays(&source, working_fdt, dtb_path);
+	if (ret)
+		goto out;
+
+	size = fdt_totalsize(working_fdt);
+	ret = env_set_hex("fw_fdt_size", size);
+	if (!ret)
+		ret = env_set_hex("fdt_addr", fdt_addr);
+	if (!ret)
+		printf("Prepared RITY devicetree at 0x%lx (%zu bytes)\n",
+		       fdt_addr, size);
+out:
+	unmap_sysmem(working_fdt);
+	return ret;
+}
+
+int mtk_fdt_prepare(void)
+{
+	return mtk_fdt_prepare_from(env_get("storage"), env_get("storage_dev"),
+				    env_get("dtb_path"));
+}
+
+static bool mtk_fdt_has_efi_target(void)
+{
+	const char *targets = env_get("boot_targets");
+	char *copy, *next, *target;
+	bool has_efi = false;
+
+	/* With no explicit policy, bootstd may still discover an EFI bootflow. */
+	if (!targets || !*targets)
+		return true;
+
+	copy = strdup(targets);
+	if (!copy)
+		return true;
+	next = copy;
+	while ((target = strsep(&next, " "))) {
+		if (*target && strcmp(target, "embedded")) {
+			has_efi = true;
+			break;
+		}
+	}
+	free(copy);
+
+	return has_efi;
+}
+
+static int mtk_fdt_post_preboot(void)
+{
+	int ret;
+
+	if (!mtk_fdt_has_efi_target())
+		return 0;
+
+	ret = mtk_fdt_prepare();
+	if (ret)
+		printf("RITY devicetree preparation failed (%d)\n", ret);
+
+	/* Keep the prompt and legacy boot path available; EFI fails via fdt_addr=0. */
+	return 0;
+}
+
+EVENT_SPY_SIMPLE(EVT_POST_PREBOOT, mtk_fdt_post_preboot);
diff --git a/arch/arm/mach-mediatek/fdt_prepare.h b/arch/arm/mach-mediatek/fdt_prepare.h
new file mode 100644
index 00000000000..5c140e3e335
--- /dev/null
+++ b/arch/arm/mach-mediatek/fdt_prepare.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef __MTK_FDT_PREPARE_H
+#define __MTK_FDT_PREPARE_H
+
+int mtk_fdt_prepare(void);
+int mtk_fdt_prepare_from(const char *storage, const char *storage_dev,
+			 const char *dtb_path);
+
+#endif

-- 
2.55.0