[PATCH] ARM: lib32: bootm: always pass a device tree to barebox images

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Since commit 828ffad14177 ("bootm: make fallback to barebox internal
tree optional"), disabling CONFIG_BOOTM_OFTREE_FALLBACK doesn't only
affect kernels, but also barebox images started with bootm. Without -o,
these now get ATAGs instead of a device tree, which leaves images like
barebox-dt-2nd.img or the STM32MP generic BL33 without any description
of the hardware and thus without an interactive console.

The option is meant to make users notice a missing kernel device tree,
but barebox images don't ship one that should be preferred over ours.
So let's have the barebox image handler preset barebox' own device tree
for bootm_get_devicetree() to use if none was supplied.

Tested on an STM32MP157C-DK2 with CONFIG_BOOTM_OFTREE_FALLBACK=n: a
zImage still gets no device tree, -o is still honoured and a chainloaded
generic BL33 image comes up with a console.

Assisted-by: Claude:opus-5.5
Fixes: 828ffad14177 ("bootm: make fallback to barebox internal tree optional")
Reported-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 arch/arm/lib32/bootm.c | 17 ++++++++++++++++-
 common/bootm.c         |  4 +++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/arm/lib32/bootm.c b/arch/arm/lib32/bootm.c
index e2a80ada788b..cfd30d1e0aff 100644
--- a/arch/arm/lib32/bootm.c
+++ b/arch/arm/lib32/bootm.c
@@ -457,9 +457,24 @@ static struct image_handler zimage_handler = {
 	.filetype = filetype_arm_zimage,
 };
 
+static int do_bootm_barebox(struct image_data *data)
+{
+	/*
+	 * Unlike a kernel, barebox doesn't ship a device tree that should be
+	 * preferred over ours: Images like barebox-dt-2nd.img and the
+	 * STM32MP generic BL33 image learn about the hardware solely from
+	 * the device tree they are passed. So pass along ours if none was
+	 * supplied, regardless of CONFIG_BOOTM_OFTREE_FALLBACK.
+	 */
+	if (!data->oftree)
+		data->of_root_node = of_dup(of_get_root_node());
+
+	return do_bootm_linux(data);
+}
+
 static struct image_handler barebox_handler = {
 	.name = "ARM barebox",
-	.bootm = do_bootm_linux,
+	.bootm = do_bootm_barebox,
 	.check_image = bootm_efi_check_image,
 	.filetype = filetype_arm_barebox,
 };
diff --git a/common/bootm.c b/common/bootm.c
index 27da1a590bf1..7ba31379a217 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -330,7 +330,9 @@ void *bootm_get_devicetree(struct image_data *data)
 			printf("using %s as devicetree\n", data->oftree->name);
 
 	} else {
-		data->of_root_node = of_dup_root_node_for_boot();
+		/* image handlers may preset barebox' own device tree */
+		if (!data->of_root_node)
+			data->of_root_node = of_dup_root_node_for_boot();
 		if (!data->of_root_node) {
 			if (bootm_verbose(data))
 				printf("using no devicetree\n");
-- 
2.47.3