board: ti: common: Introduce a common fdt ops library

Introduce a common fdt operations library for basic device tree
operations that are common between various boards.

The first library to introduce here is the capability to set up
fdtfile as a standard variable as part of board identification rather
than depend on scripted ifdeffery.

Reviewed-by: Jonathan Humphreys <j-humphreys@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Nishanth Menon <nm@ti.com>

board/ti/common/Kconfig

@@ -49,3 +49,15 @@ config TI_COMMON_CMD_OPTIONS
 	imply CMD_SPI
 	imply CMD_TIME
 	imply CMD_USB if USB
+
+config TI_FDT_FOLDER_PATH
+	string "Location of Folder path where dtb is present"
+	default "ti/davinci" if ARCH_DAVINCI
+	default "ti/keystone" if ARCH_KEYSTONE
+	default "ti/omap" if ARCH_OMAP2PLUS
+	default "ti" if ARCH_K3
+	depends on ARCH_DAVINCI || ARCH_KEYSTONE || ARCH_OMAP2PLUS || ARCH_K3
+	help
+	   Folder path for kernel device tree default.
+	   This is used along with fdtfile path to locate the kernel
+	   device tree blob.

board/ti/common/Makefile

@@ -3,3 +3,4 @@
 
 obj-${CONFIG_TI_I2C_BOARD_DETECT} += board_detect.o
 obj-${CONFIG_CMD_EXTENSION} += cape_detect.o
+obj-${CONFIG_OF_LIBFDT} += fdt_ops.o

board/ti/common/fdt_ops.c

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Library to support FDT file operations which are common
+ *
+ * Copyright (C) 2024 Texas Instruments Incorporated - https://www.ti.com/
+ */
+
+#include <env.h>
+#include <vsprintf.h>
+#include "fdt_ops.h"
+
+void ti_set_fdt_env(const char *board_name, struct ti_fdt_map *fdt_map)
+{
+	char *fdt_file_name = NULL;
+	char fdtfile[TI_FDT_FILE_MAX];
+
+	if (board_name) {
+		while (fdt_map) {
+			/* Check for NULL terminator in the list */
+			if (!fdt_map->board_name)
+				break;
+			if (!strncmp(fdt_map->board_name, board_name, TI_BOARD_NAME_MAX)) {
+				fdt_file_name = fdt_map->fdt_file_name;
+				break;
+			}
+			fdt_map++;
+		}
+	}
+
+	/* match not found OR null board_name */
+	if (!fdt_file_name) {
+		/*
+		 * Prioritize CONFIG_DEFAULT_FDT_FILE - if that is not defined,
+		 * or is empty, then use CONFIG_DEFAULT_DEVICE_TREE
+		 */
+#ifdef CONFIG_DEFAULT_FDT_FILE
+		if (strlen(CONFIG_DEFAULT_FDT_FILE)) {
+			snprintf(fdtfile, sizeof(fdtfile), "%s/%s",
+				 CONFIG_TI_FDT_FOLDER_PATH, CONFIG_DEFAULT_FDT_FILE);
+		} else
+#endif
+		{
+			snprintf(fdtfile, sizeof(fdtfile), "%s/%s.dtb",
+				 CONFIG_TI_FDT_FOLDER_PATH, CONFIG_DEFAULT_DEVICE_TREE);
+		}
+	} else {
+		snprintf(fdtfile, sizeof(fdtfile), "%s/%s", CONFIG_TI_FDT_FOLDER_PATH,
+			 fdt_file_name);
+	}
+
+	env_set("fdtfile", fdtfile);
+
+	/*
+	 * XXX: DEPRECATION WARNING: 2 u-boot versions (2024.10).
+	 *
+	 * Maintain compatibility with downstream scripts that may be using
+	 * name_fdt
+	 */
+	if (board_name)
+		env_set("name_fdt", fdtfile);
+	/* Also set the findfdt legacy script to warn users to stop using this */
+	env_set("findfdt",
+		"echo WARN: fdtfile already set. Stop using findfdt in script");
+}

board/ti/common/fdt_ops.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Library to support common device tree manipulation for TI EVMs
+ *
+ * Copyright (C) 2024 Texas Instruments Incorporated - https://www.ti.com
+ */
+
+#ifndef __FDT_OPS_H
+#define __FDT_OPS_H
+
+#define TI_BOARD_NAME_MAX 20
+#define TI_FDT_FILE_MAX 200
+
+/**
+ *  struct ti_fdt_map - mapping of device tree blob name to board name
+ *  @board_name: board_name up to TI_BOARD_NAME_MAX long
+ *  @fdt_file_name: device tree blob name as described by kernel
+ */
+struct ti_fdt_map {
+	const char *board_name;
+	char *fdt_file_name;
+};
+
+/**
+ * ti_set_fdt_env  - Find the correct device tree file name based on the
+ * board name and set 'fdtfile' env variable with correct folder
+ * structure appropriate to the architecture and Linux kernel's
+ * 'make install_dtbs' conventions. This function is invoked typically
+ * as part of board_late_init.
+ *
+ * fdt name is picked by:
+ * a) If a board name match is found, use the match
+ * b) If not, CONFIG_DEFAULT_FDT_FILE (Boot OS device tree) if that is defined
+ *    and not null
+ * c) If not, Use CONFIG_DEFAULT_DEVICE_TREE (DT control for bootloader)
+ *
+ * @board_name: match to search with (max of TI_BOARD_NAME_MAX chars)
+ * @fdt_map: NULL terminated array of device tree file name matches.
+ */
+void ti_set_fdt_env(const char *board_name, struct ti_fdt_map *fdt_map);
+
+#endif /* __FDT_OPS_H */