fdt: Add a command to show reserved-memory regions

Add a new 'fdt reserved' subcommand that displays all reserved memory
regions defined in the device tree's /reserved-memory node. This command
provides a formatted table showing the ID, name, start address, and size
of each reserved memory region.

Avoid a conflict with the existing 'fdt resize' command. Update the docs
and add a test.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

boot/fdt_support.c

@@ -2265,7 +2265,7 @@ void fdt_print_reserved(void *fdt)
 	int node, reserved, id;
 	int addr_cells, size_cells;
 
-	printf("%-4s %-20s %-18s %-18s\n", "ID", "Name", "Start", "Size");
+	printf("%-4s %-20s %-16s %-16s\n", "ID", "Name", "Start", "Size");
 	printf("--------------------------------------------------------"
 	       "--------\n");
 
@@ -2300,7 +2300,7 @@ void fdt_print_reserved(void *fdt)
 				rsv_size = (rsv_size << 32) |
 					   fdt32_to_cpu(reg[cells++]);
 
-			printf("%-4d %-20s 0x%-16llx 0x%-16llx\n",
+			printf("%-4d %-20s %-16llx %-16llx\n",
 			       id++, name ? name : "(unnamed)", rsv_start,
 			       rsv_size);
 		} else {

cmd/Kconfig

@@ -495,6 +495,16 @@ config CMD_FDT
 	help
 	  Do FDT related setup before booting into the Operating System.
 
+config CMD_FDT_RESERVED
+	bool "fdt subcommand to show reserved memory"
+	depends on CMD_FDT
+	default y if SANDBOX || EFI_APP
+	help
+	  Provides an 'fdt reserved' command which shows a list of the
+	  reserved-memory regions in the devicetree, before booting into the
+	  Operating System. Note that this is differen from 'fdt rsvmem'
+	  which shows the reserve entries after the FDT header.
+
 config SUPPORT_EXTENSION_SCAN
 	bool
 

cmd/fdt.c

@@ -768,8 +768,13 @@ static int do_fdt(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 			return CMD_RET_FAILURE;
 	}
 #endif
+	/* print reserved memory regions */
+	else if (IS_ENABLED(CONFIG_CMD_FDT_RESERVED) &&
+		 !strncmp(argv[1], "rese", 4)) {
+		fdt_print_reserved(working_fdt);
+
 	/* resize the fdt */
-	else if (strncmp(argv[1], "re", 2) == 0) {
+	} else if (strncmp(argv[1], "re", 2) == 0) {
 		uint extrasize;
 		if (argc > 2)
 			extrasize = hextoul(argv[2], NULL);
@@ -902,6 +907,9 @@ U_BOOT_LONGHELP(fdt,
 #endif
 	"fdt move   <fdt> <newaddr> <length> - Copy the fdt to <addr> and make it active\n"
 	"fdt resize [<extrasize>]            - Resize fdt to size + padding to 4k addr + some optional <extrasize> if needed\n"
+#ifdef CONFIG_CMD_FDT_RESERVED
+	"fdt reserved                        - Print reserved-memory regions\n"
+#endif
 	"fdt print  <path> [<prop>]          - Recursive print starting at <path>\n"
 	"fdt list   <path> [<prop>]          - Print one level starting at <path>\n"
 	"fdt get value <var> <path> <prop> [<index>] - Get <property> and store in <var>\n"

doc/usage/cmd/fdt.rst

@@ -12,6 +12,7 @@ Synopsis
 ::
 
     fdt addr [-cq] [addr [len]]
+    fdt reserved
 
 Description
 -----------
@@ -48,6 +49,24 @@ If the `len` argument is provided, then the device tree is expanded to that
 size. This can be used to make space for more nodes and properties. It is
 assumed that there is enough space in memory for this expansion.
 
+fdt reserved
+~~~~~~~~~~~~
+
+This command prints all reserved memory regions defined in the device tree's
+`/reserved-memory` node. The output shows a formatted table with the following
+columns:
+
+- **ID**: Sequential number for each region
+- **Name**: Node name of the reserved memory region
+- **Start**: Start address of the reserved memory region in hexadecimal
+- **Size**: Size of the reserved memory region in hexadecimal
+
+If no `/reserved-memory` node exists in the device tree, the command will
+display an appropriate message. This command is useful for debugging memory
+layout issues and verifying that reserved memory regions are properly defined.
+
+This subcommand is only present is `CONFIG_CMD_FDT_RESERVED` is enabled.
+
 Example
 -------
 
@@ -67,6 +86,15 @@ address and expand it to 0xf000 in size::
     => md 10000 4
     00010000: edfe0dd0 00f00000 78000000 7c270000  ...........x..'|
 
+Print all reserved memory regions::
+
+    => fdt reserved
+    ID   Name                 Start              Size
+    ----------------------------------------------------------------
+    0    secmon@1f000000      0x000000001f000000 0x0000000001000000
+    1    atf@40000000         0x0000000040000000 0x0000000000200000
+    2    linux,cma            0x0000000050000000 0x0000000008000000
+
 Return value
 ------------
 

test/cmd/fdt.c

@@ -1464,3 +1464,43 @@ static int fdt_test_apply(struct unit_test_state *uts)
 	return 0;
 }
 FDT_TEST(fdt_test_apply, UTF_CONSOLE);
+
+/* Test 'fdt reserved' reading reserved-memory nodes */
+static int fdt_test_reserved(struct unit_test_state *uts)
+{
+	struct fdt_header *old_working_fdt;
+	char fdt[8192];
+	ulong addr;
+
+	if (!IS_ENABLED(CONFIG_SANDBOX))
+		return -EAGAIN;
+
+	/* Save the original working_fdt */
+	old_working_fdt = working_fdt;
+
+	/* Set working_fdt to control FDT (sandbox has reserved memory) */
+	working_fdt = (struct fdt_header *)gd->fdt_blob;
+
+	ut_assertok(run_command("fdt reserved", 0));
+
+	/* Just verify we get the header */
+	ut_assert_nextlinen("ID");
+	ut_assert_nextlinen("------");
+
+	/* Verify we get a tcg_event_log entry with correct address/size */
+	ut_assert_nextline("0    tcg_event_log        100000           2000            ");
+
+	/* Test with FDT that has no reserved-memory node */
+	ut_assertok(make_test_fdt(uts, fdt, sizeof(fdt), &addr));
+	ut_assertok(run_command("fdt reserved", 0));
+	ut_assert_nextlinen("ID   Name                 Start            Size");
+	ut_assert_nextline("----------------------------------------------------------------");
+	ut_assert_nextline("No /reserved-memory node found in device tree");
+	ut_assert_console_end();
+
+	/* Restore the original working_fdt */
+	working_fdt = old_working_fdt;
+
+	return 0;
+}
+FDT_TEST(fdt_test_reserved, UTF_CONSOLE);