[RFC] Raspberry Pi: copy /system/linux, {serial, revision} from firmware
Simon Glass
sjg at chromium.org
Sat Feb 15 13:05:50 CET 2025
Hi Fiona,
On Tue, 11 Feb 2025 at 07:56, Fiona Klute <fiona.klute at gmx.de> wrote:
>
> Both the Raspberry Pi downstream kernel [1] and some userspace tools
> [2] use the revision property to identify the board, and the latter
> fails if it is absent. The firmware creates the /system node, so we
> need to do the same.
>
> [1] https://github.com/raspberrypi/linux/blob/0f292fbb6346b05766152902076895558ac23f9a/arch/arm/mach-bcm/board_bcm2835.c#L23-L33
> [2] https://github.com/jgarff/rpi_ws281x/blob/7fc0bf8b31d715bbecf28e852ede5aaa388180da/rpihw.c#L579
>
> Signed-off-by: Fiona Klute <fiona.klute at gmx.de>
> Cc: Matthias Brugger <mbrugger at suse.com>
> Cc: Peter Robinson <pbrobinson at gmail.com>
> Cc: Tom Rini <trini at konsulko.com>
> ---
> I'm sending this as RFC because I'm not sure if creating a temporary
> overlay is the best approach here, advice on a better way to create the
> /system node if needed is very much welcome. I know I'll need to add
> more error checks, I'll do that after I know I have the right approach.
>
> board/raspberrypi/rpi/rpi.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>From my side, if my rpi seriesl[1] results in my becoming a rpi
maintainer, I'll take a look at this and other pending rpi patches.
>
> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
> index aa39afa338a..647716127c7 100644
> --- a/board/raspberrypi/rpi/rpi.c
> +++ b/board/raspberrypi/rpi/rpi.c
> @@ -550,6 +550,41 @@ int copy_property(void *dst, void *src, char *path, char *property)
> return fdt_setprop(dst, dst_offset, property, prop, len);
> }
>
> +int copy_system_node(void *fdt, void *fw_fdt)
> +{
> + const fdt32_t *prop;
> + char fdto[2048];
> + int src_offset;
> + int len;
> +
> + src_offset = fdt_path_offset(fw_fdt, "/system");
> + if (src_offset < 0)
> + return -1;
> +
> + fdt_create(fdto, sizeof(fdto));
> + fdt_finish_reservemap(fdto);
> + fdt_begin_node(fdto, "");
> + fdt_begin_node(fdto, "fragment");
> + fdt_property_string(fdto, "target-path", "/");
> + fdt_begin_node(fdto, "__overlay__");
> + fdt_begin_node(fdto, "system");
> +
> + prop = fdt_getprop(fw_fdt, src_offset, "linux,serial", &len);
> + if (prop)
> + fdt_property(fdto, "linux,serial", prop, len);
> + prop = fdt_getprop(fw_fdt, src_offset, "linux,revision", &len);
> + if (prop)
> + fdt_property(fdto, "linux,revision", prop, len);
> +
> + fdt_end_node(fdto);
> + fdt_end_node(fdto);
> + fdt_end_node(fdto);
> + fdt_end_node(fdto);
> + fdt_finish(fdto);
> +
> + fdt_overlay_apply_verbose(fdt, fdto);
> +}
> +
> /* Copy tweaks from the firmware dtb to the loaded dtb */
> void update_fdt_from_fw(void *fdt, void *fw_fdt)
> {
> @@ -560,6 +595,8 @@ void update_fdt_from_fw(void *fdt, void *fw_fdt)
> /* The firmware provides a more precise model; so copy that */
> copy_property(fdt, fw_fdt, "/", "model");
>
> + copy_system_node(fdt, fw_fdt);
> +
> /* memory reserve as suggested by the firmware */
> copy_property(fdt, fw_fdt, "/", "memreserve");
>
> --
> 2.47.2
>
Regards,
Simon
[1] https://patchwork.ozlabs.org/project/uboot/list/?series=437666
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