[U-Boot] [PATCH v8 20/30] efi: Tidy up device-tree-size calculation in copy_fdt()

[Simon Glass]

This is a bit confusing at present since it adds 4KB to the pointer, then
rounds it up. It looks like a bug, but is not.

Move the 4KB addition into a separate statement and expand the comment.

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

Changes in v8: None
Changes in v7: None
Changes in v6: None
Changes in v5: None
Changes in v4: None
Changes in v3: None
Changes in v2: None

 cmd/bootefi.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/cmd/bootefi.c b/cmd/bootefi.c
index d2458e2397..c89f83fb33 100644
--- a/cmd/bootefi.c
+++ b/cmd/bootefi.c
@@ -137,8 +137,12 @@ static void *copy_fdt(void *fdt)
 			fdt_ram_start = ram_start;
 	}
 
-	/* Give us at least 4kb breathing room */
-	fdt_size = ALIGN(fdt_size + 4096, EFI_PAGE_SIZE);
+	/*
+	 * Give us at least 4KB of breathing room in case the device tree needs
+	 * to be expanded later. Round up to the nearest EFI page boundary.
+	 */
+	fdt_size += 4096;
+	fdt_size = ALIGN(fdt_size + EFI_PAGE_SIZE - 1, EFI_PAGE_SIZE);
 	fdt_pages = fdt_size >> EFI_PAGE_SHIFT;
 
 	/* Safe fdt location is at 127MB */
-- 
2.18.0.rc1.244.gcf134e6275-goog