Hi Wadim,
On 8/24/26 2:06 PM, Wadim Egorov wrote:
Set /chosen/bootsource in the device tree passed to the OS to the full
path of the node of the device the BootROM booted from.
Please consider implementing this for *all* DTBs, not only the one we
pass to the OS. e.g. this is also quite useful in U-Boot proper itself
for checking which boot medium was used by the BootROM and which one was
used by the SPL to load U-Boot (via /chosen/u-boot,spl-boot-device; and
e.g. verify fallback mechanisms).
Platforms provide the path by implementing bootsource_get_ofpath(). The
property is only set if the device tree passed to the OS has a node at
that path.
Signed-off-by: Wadim Egorov <[email protected]>
---
boot/Kconfig | 8 ++++++++
boot/fdt_support.c | 30 +++++++++++++++++++++++++++++
doc/device-tree-bindings/chosen.txt | 9 +++++++++
include/fdt_support.h | 12 ++++++++++++
4 files changed, 59 insertions(+)
diff --git a/boot/Kconfig b/boot/Kconfig
index c67dc0ba493..0dbd715999d 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -1922,6 +1922,14 @@ config OF_SYSTEM_SETUP
system-specific information in the device tree for use by the OS.
The device tree is then passed to the OS.
+config FDT_FIXUP_BOOTSOURCE
+ bool "Add the BootROM boot source to the device tree before boot"
+ help
+ Record the device the SoC's BootROM loaded the very first boot
+ stage from as the /chosen/bootsource property in the device
+ tree passed to the OS.
+ The platform must implement bootsource_get_ofpath().
+
Do we *really* need a Kconfig symbol for this? Why not always add it?
If you're attempting to implement a generic solution, it'd be good to
switch the only implementer today (Rockchip, via spl_perform_arch_fixups
in arch/arm/mach-rockchip/spl-boot-order.c) to that generic solution.
config OF_STDOUT_VIA_ALIAS
bool "Update the device-tree stdout alias from U-Boot"
help
diff --git a/boot/fdt_support.c b/boot/fdt_support.c
index 2941df55996..95644b9b67c 100644
--- a/boot/fdt_support.c
+++ b/boot/fdt_support.c
@@ -334,6 +334,33 @@ __weak const char *board_fdt_chosen_bootargs(const struct
fdt_property *fdt_ba)
return env_get("bootargs");
}
+__weak const char *bootsource_get_ofpath(void)
+{
+ return NULL;
+}
+
+static void fdt_setup_bootsource(void *fdt, int chosen)
+{
+ const char *path;
+ int err;
+
+ path = bootsource_get_ofpath();
+ if (!path)
+ return;
+
+ /* Only record a path this tree has a node at, so the OS can resolve it
*/
+ if (fdt_path_offset(fdt, path) < 0) {
+ debug("%s: no node %s, not setting bootsource\n",
+ __func__, path);
+ return;
+ }
+
+ err = fdt_setprop_string(fdt, chosen, "bootsource", path);
+ if (err < 0)
+ printf("WARNING: could not set bootsource %s.\n",
+ fdt_strerror(err));
+}
+
int fdt_chosen(void *fdt)
{
struct abuf buf = {};
@@ -353,6 +380,9 @@ int fdt_chosen(void *fdt)
if (nodeoffset < 0)
return nodeoffset;
+ if (IS_ENABLED(CONFIG_FDT_FIXUP_BOOTSOURCE))
+ fdt_setup_bootsource(fdt, nodeoffset);
+
/* if DM_RNG enabled automatically inject kaslr-seed node unless:
* CONFIG_MEASURED_BOOT enabled: as dt modifications break measured boot
* CONFIG_ARMV8_SEC_FIRMWARE_SUPPORT enabled: as that implementation
does not use dm yet
diff --git a/doc/device-tree-bindings/chosen.txt
b/doc/device-tree-bindings/chosen.txt
index c8312540f57..5d737feb48b 100644
--- a/doc/device-tree-bindings/chosen.txt
+++ b/doc/device-tree-bindings/chosen.txt
@@ -114,6 +114,15 @@ of where said later stage was booted from.
You should not define this property yourself in the device-tree, as it
may be overwritten without warning.
+bootsource property
+-------------------
+
+This property is defined in the dt-schema chosen.yaml binding and
+holds the full path of the node of the device the BootROM booted from.
+With CONFIG_FDT_FIXUP_BOOTSOURCE enabled, U-Boot sets it in the device
+tree passed to the OS if the platform implements bootsource_get_ofpath()
+and that tree has a node at the returned path.
+
Do we really need to describe something that's already in the standard?
firmware-loader property
------------------------
Multiple file system firmware loader nodes could be defined in device trees
for
diff --git a/include/fdt_support.h b/include/fdt_support.h
index 47b8b63d13d..db2611da750 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -55,6 +55,18 @@ int fdt_root(void *fdt);
*/
int fdt_chosen(void *fdt);
+/**
+ * bootsource_get_ofpath() - get the node path of the BootROM boot device
The boot medium the BootROM used to load the very first stage after itself.
+ *
+ * Platforms implement this so fdt_chosen() can set /chosen/bootsource in
+ * the device tree passed to the OS. The property is only set if that
+ * tree has a node at the returned path, so use the node name from the
Not the node name, the node *path*.
+ * SoC device tree.
If the boot device is a NOR flash for example, then we could have
/path/to/spi/flash@0 and flash@0 is very unlikely to be described in the
SoC include device tree. I'm not sure what you were trying to convey
here, can you clarify what you're trying to prevent the user from doing?
Cheers,
Quentin
