> -----Original Message-----
> From: U-Boot <[email protected]> On Behalf Of Simon Glass
> Sent: Tuesday, December 10, 2024 4:55 AM
> To: U-Boot Mailing List <[email protected]>
> Cc: Tom Rini <[email protected]>; Stephen Warren <[email protected]>;
> Stephen Warren
> <[email protected]>; Matthias Brugger <[email protected]>; Simon Glass
> <[email protected]>; Francois
> Berder <[email protected]>; Ivan T. Ivanov <[email protected]>; Patrick Rudolph
> <[email protected]>; Peter Robinson <[email protected]>;
> Rasmus Villemoes
> <[email protected]>
> Subject: [PATCH v3 5/5] rpi: Use the U-Boot control FDT for fdt_addr
>
> The fdt_addr variable is used in extlinux as a fallback devicetree if
> none is provided by the boot command.
>
> The existing mechanism uses the devicetree provided to U-Boot, but in
> its original, unrelocated position. For the rpi_4 I am using, this is
> 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.
>
> In version 2, it incorporates some changes to fdt_addr, etc. suggested
> by Tom, as well as adding myself as a maintainer.
>
> Signed-off-by: Simon Glass <[email protected]>
Reviewed-by: Jaehoon Chung <[email protected]>
Tested-by: Jaehoon Chung <[email protected]>
> ---
>
> (no changes since v2)
>
> Changes in v2:
> - Drop patch to allow expanding the devicetree during relocation
>
> board/raspberrypi/rpi/rpi.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
> index 9122f33d88d..8f6ab1b1b9b 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>
> @@ -325,19 +327,10 @@ static void set_fdtfile(void)
> env_set("fdtfile", fdtfile);
> }
>
> -/*
> - * 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
> */
> static void set_fdt_addr(void)
> {
> - if (env_get("fdt_addr"))
> - return;
> -
> - 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);
> }
>
> /*
> @@ -572,7 +565,10 @@ 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);
>
> node = fdt_node_offset_by_compatible(blob, -1, "simple-framebuffer");
> if (node < 0)
> --
> 2.34.1
