[PATCH 2/3] fdt: Allow expanding the devicetree during relocation

[Simon Glass]

Some boards set fdt_high to -1 which means that the FDT is not relocated
in boot_relocate_fdt().

A comment in that function says that we assume there is space after the
existing fdt to use for padding, with the padding size set to
CONFIG_SYS_FDT_PAD

However, there is no guarantee that this space is available. If using
the control FDT, then global_data is immediately above it, so expanding
the FDT and adding FDT properties will cause U-Boot to fail.

Add a new Kconfig option to provide the required space, enabling it by
default.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 common/board_f.c |  6 ++++--
 dts/Kconfig      | 11 +++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/common/board_f.c b/common/board_f.c
index 8baaa2341a3..ed30aeeab23 100644
--- a/common/board_f.c
+++ b/common/board_f.c
@@ -553,8 +553,10 @@ static int reserve_fdt(void)
 		 * section, then it will be relocated with other data.
 		 */
 		if (gd->fdt_blob) {
-			gd->boardf->fdt_size =
-				ALIGN(fdt_totalsize(gd->fdt_blob), 32);
+			int size = fdt_totalsize(gd->fdt_blob);
+
+			gd->boardf->fdt_size = ALIGN(size + CONFIG_OF_EXPAND,
+						     32);
 
 			gd->start_addr_sp = reserve_stack_aligned(
 				gd->boardf->fdt_size);
diff --git a/dts/Kconfig b/dts/Kconfig
index 41a758e83a6..360611edd01 100644
--- a/dts/Kconfig
+++ b/dts/Kconfig
@@ -219,6 +219,17 @@ config OF_OMIT_DTB
 	  This is used for boards which normally provide a devicetree via a
 	  runtime mechanism (such as OF_BOARD), to avoid confusion.
 
+config OF_EXPAND
+	hex # "Amount to allow the control FDT to expand"
+	default SYS_FDT_PAD if OF_LIBFDT
+	default 0
+	help
+	  Some boards make use of the control FDT to boot an OS, thus when
+	  image_setup_libfdt() adds extra things to the end of the FDT, there
+	  needs to be enough space.
+
+	  Set this to the number of bytes of extra space required for the FDT.
+
 config DEFAULT_DEVICE_TREE
 	string "Default Device Tree for DT control"
 	depends on OF_CONTROL
-- 
2.34.1