The fdt_addr variable is used in extlinux as a fallback devicetree if
none is provided by the boot command. Otherwise the only use in U-Boot
seems to me efi_install_fdt() when the internal FDT is required.
The existing mechanism uses the devicetree provided to U-Boot, but in
its original, unrelocated position. In my testing on an rpi_4, this ends
up at 2b35ef00 which is not a convenient place in memory, if the ramdisk
is large.
U-Boot already deals with this sort of problem by relocating the FDT
to a safe address.
So use the control-FDT address instead.
Remove the existing comment, which is confusing, since the FDT is not
actually passed unmodified to the kernel: U-Boot adds various things
using its FDT-fixup mechanism.
Note that board_get_usable_ram_top() reduces the RAM top for boards with
less RAM. This behaviour is left unchanged as there is no other
mechanism for U-Boot to handle this.
Signed-off-by: Simon Glass <s...@chromium.org>
Reviewed-by: Christopher Obbard <christopher.obb...@linaro.org>
Tested-by: Christopher Obbard <christopher.obb...@linaro.org> # CM4 1G
---
Changes in v5:
- Rebase to -next
- Drop patch to add myself as a maintainer
Changes in v4:
- Expand the comment on set_fdt_addr()
- Update the commit message to talk in terms of my testing
Changes in v2:
- Drop patch to allow expanding the devicetree during relocation
board/raspberrypi/rpi/rpi.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index 1b0b664fa2b..6f96c1ebc96 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -3,6 +3,8 @@
* (C) Copyright 2012-2016 Stephen Warren
*/
+#define LOG_CATEGORY LOGC_BOARD
+
#include <config.h>
#include <dm.h>
#include <env.h>
@@ -354,15 +356,13 @@ static void set_fdtfile(void)
}
/*
- * If the firmware provided a valid FDT at boot time, let's expose it in
- * ${fdt_addr} so it may be passed unmodified to the kernel.
+ * Allow U-Boot to use its control FDT with extlinux if one is not provided.
+ * This will then go through the usual fixups that U-Boot does, before being
+ * handed off to Linux
*/
static void set_fdt_addr(void)
{
- if (fdt_magic(fw_dtb_pointer) != FDT_MAGIC)
- return;
-
- env_set_hex("fdt_addr", fw_dtb_pointer);
+ env_set_hex("fdt_addr", (ulong)gd->fdt_blob);
}
/*
@@ -608,7 +608,10 @@ int ft_board_setup(void *blob, struct bd_info *bd)
{
int node;
- update_fdt_from_fw(blob, (void *)fw_dtb_pointer);
+ if (blob == gd->fdt_blob)
+ log_debug("Same FDT: nothing to do\n");
+ else
+ update_fdt_from_fw(blob, (void *)gd->fdt_blob);
if (CONFIG_IS_ENABLED(FDT_SIMPLEFB)) {
node = fdt_node_offset_by_compatible(blob, -1,
"simple-framebuffer");
--
2.43.0
