boot/bootfdt: Add smbios3-entrypoint to FDT for non-EFI boots

The Linux kernel can discover SMBIOS tables through two primary methods:
1. Via EFI tables, when using EFI boot;
2. Via the 'smbios3-entrypoint' property in the /chosen node of the
device tree.

When U-Boot boots a Linux kernel using a non-EFI command ("bootm",
"bootz", or "booti"), the kernel relies on the device tree to detect
the hardware. If SMBIOS tables are available in U-Boot, they should
be passed to the kernel via this device tree property.

This patch modifies boot_fdt_prepare(), to inject the SMBIOSv3 table
address into the device tree if there is a table generated by U-boot.
The "board_fdt_chosen_smbios" is weak in order to leave the possibilty
for specific boards to select custom SMBIOS addresses.

The changes in this patch are added in the context of supporting this
device tree property in linux kernel:
https://lkml.org/lkml/2025/10/24/1393

Device tree schema was updated to include the "smbios3-entrypoint" node
in pull request: https://github.com/devicetree-org/dt-schema/pull/177

Signed-off-by: Adriana Nicolae <[email protected]>

2 files changed, 57 insertions, 0 deletions

diff --git a/test/cmd/fdt.c b/test/cmd/fdt.c
index 4c3c6308ab4..a121b294185 100644
--- a/test/cmd/fdt.c
+++ b/test/cmd/fdt.c
@@ -1274,6 +1274,7 @@ static int fdt_test_chosen(struct unit_test_state *uts)
 	char fdt[8192];
 	struct udevice *dev;
 	ulong addr;
+	ulong smbiosaddr = gd_smbios_start();
 
 	ut_assertok(make_test_fdt(uts, fdt, sizeof(fdt), &addr));
 	fdt_shrink_to_minimum(fdt, 4096);	/* Resize with 4096 extra bytes */
@@ -1292,6 +1293,10 @@ static int fdt_test_chosen(struct unit_test_state *uts)
 		ut_assert(0 < console_record_readline(uts->actual_str,
 						      sizeof(uts->actual_str)));
 	ut_asserteq_str("chosen {", uts->actual_str);
+	if (CONFIG_IS_ENABLED(GENERATE_SMBIOS_TABLE))
+		ut_assert_nextline("\tsmbios3-entrypoint = <0x%08x 0x%08x>;",
+				   upper_32_bits(smbiosaddr),
+				   lower_32_bits(smbiosaddr));
 	ut_assert_nextlinen("\tu-boot,version = "); /* Ignore the version string */
 	if (env_bootargs)
 		ut_assert_nextline("\tbootargs = \"%s\";", env_bootargs);
@@ -1316,6 +1321,10 @@ static int fdt_test_chosen(struct unit_test_state *uts)
 			   lower_32_bits(0x1234 + 0x5678 - 1));
 	ut_assert_nextline("\tlinux,initrd-start = <0x%08x 0x%08x>;",
 			   upper_32_bits(0x1234), lower_32_bits(0x1234));
+	if (CONFIG_IS_ENABLED(GENERATE_SMBIOS_TABLE))
+		ut_assert_nextline("\tsmbios3-entrypoint = <0x%08x 0x%08x>;",
+				   upper_32_bits(smbiosaddr),
+				   lower_32_bits(smbiosaddr));
 	ut_assert_nextlinen("\tu-boot,version = "); /* Ignore the version string */
 	if (env_bootargs)
 		ut_assert_nextline("\tbootargs = \"%s\";", env_bootargs);
diff --git a/test/dm/fdtdec.c b/test/dm/fdtdec.c
index 1f24f1d5dff..ea5a494612c 100644
--- a/test/dm/fdtdec.c
+++ b/test/dm/fdtdec.c
@@ -7,6 +7,9 @@
 #include <asm/global_data.h>
 #include <dm/of_extra.h>
 #include <dm/test.h>
+#include <fdt_support.h>
+#include <mapmem.h>
+#include <smbios.h>
 #include <test/ut.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -129,3 +132,48 @@ static int dm_test_fdtdec_add_reserved_memory(struct unit_test_state *uts)
 }
 DM_TEST(dm_test_fdtdec_add_reserved_memory,
 	UTF_SCAN_PDATA | UTF_SCAN_FDT | UTF_FLAT_TREE);
+
+static int dm_test_fdt_chosen_smbios(struct unit_test_state *uts)
+{
+	void *blob;
+	ulong val;
+	struct smbios3_entry *entry;
+	int chosen, blob_sz;
+	const fdt64_t *prop;
+
+	if (!CONFIG_IS_ENABLED(GENERATE_SMBIOS_TABLE)) {
+		return -EAGAIN;
+	}
+
+	blob_sz = fdt_totalsize(gd->fdt_blob) + 4096;
+	blob = memalign(8, blob_sz);
+	ut_assertnonnull(blob);
+
+	/* Make a writable copy of the fdt blob */
+	ut_assertok(fdt_open_into(gd->fdt_blob, blob, blob_sz));
+
+	/* Mock SMBIOS table */
+	entry = map_sysmem(gd->arch.smbios_start, sizeof(struct smbios3_entry));
+	memcpy(entry->anchor, "_SM3_", 5);
+	entry->length = sizeof(struct smbios3_entry);
+	unmap_sysmem(entry);
+
+	/* Force fdt_chosen to run */
+	ut_assertok(fdt_chosen(blob));
+
+	chosen = fdt_path_offset(blob, "/chosen");
+	ut_assert(chosen >= 0);
+
+	/* Verify the property exists */
+	prop = fdt_getprop(blob, chosen, "smbios3-entrypoint", NULL);
+	ut_assertnonnull(prop);
+
+	/* Verify the property matches smbios_start */
+	val = fdt64_to_cpu(*prop);
+	ut_asserteq_64(gd->arch.smbios_start, val);
+
+	free(blob);
+
+	return 0;
+}
+DM_TEST(dm_test_fdt_chosen_smbios, UTF_SCAN_PDATA | UTF_SCAN_FDT);