[PATCH] ARM: fdt: copy TF-A reserved memory into fdt passed to Linux

[Alexander Sverdlin]

Currently some ARM-based platforms reserve TF-A memory in their own ways:
- Mediatek gets BL31 region via SMC call in ft_system_setup()
- K3 uses CONFIG_K3_ATF_LOAD_ADDR, effectively in ft_system_setup()

And others like Allwinner simply forget to do it, which results in Linux
overwriting TF-A and crashing.

Unfortunately seems that the things are not much better on TF-A side and
there is no universal way to get the reserved memory region across
platforms. But there is at least a most common way in TF-A, namely
reserving  memory range in the FDT, in particular:
- Allwinner	("tf-a at 40000000" node)
- ARM FPGA	("tf-a at 80000000" node)
- Xilinx	("tf-a" node)

While this patch aims to improve the situation for Allwinner platforms,
it's deliberately adding more generic code to pave the potential way of
unification for other platforms.

Note that fdtdec_add_reserved_memory() has a check for an already existing
carveout with exactly matching boundaries and will not create a duplicate
even if the name doesn't match. It would not however detect an already
existing bigger carveout fully containing the one requested.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin at gmail.com>
---
The patch has been developed to faciliate Allwinner A133 SoC support, where
most of the work currently happens on TF-A [1] and Linux [2] sides, but
I wanted to send this patch upfront to get the first feedback and because
already supported H616 SoC would already benefit from the patch.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/49754
[2] https://lore.kernel.org/all/20260605070923.3045073-1-alexander.sverdlin@gmail.com/
[3] https://lore.kernel.org/all/b428d57ba5464f1226daf099877f4c25fa4fc191.camel@gmail.com/

 arch/arm/lib/bootm-fdt.c | 55 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/arch/arm/lib/bootm-fdt.c b/arch/arm/lib/bootm-fdt.c
index 2671f9a0ebf..19d917943c1 100644
--- a/arch/arm/lib/bootm-fdt.c
+++ b/arch/arm/lib/bootm-fdt.c
@@ -14,7 +14,9 @@
  * Copyright (C) 2001  Erik Mouw (J.A.K.Mouw at its.tudelft.nl)
  */
 
+#include <dm/ofnode.h>
 #include <fdt_support.h>
+#include <linux/ioport.h>
 #ifdef CONFIG_ARMV7_NONSEC
 #include <asm/armv7.h>
 #endif
@@ -24,6 +26,52 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+static int tfa_copy_reserved_memory(void *new_blob)
+{
+#ifdef CONFIG_OF_CONTROL
+	ofnode node, subnode;
+
+	/*
+	 * TF-A for several platforms inserts its memory region as
+	 * reserved-memory node
+	 */
+	node = ofnode_path("/reserved-memory");
+	if (!ofnode_valid(node))
+		return 0;
+
+	ofnode_for_each_subnode(subnode, node) {
+		struct fdt_memory carveout;
+		struct resource res;
+		const char *name;
+		int ret;
+
+		name = ofnode_get_name(subnode);
+		if (!name)
+			return -FDT_ERR_BADSTRUCTURE;
+
+		/* only handle TF-A reservations */
+		if (strncmp(name, "tf-a", 4))
+			continue;
+
+		/* check if this subnode has a reg property */
+		ret = ofnode_read_resource(subnode, 0, &res);
+		if (ret)
+			continue;
+
+		carveout.start = res.start,
+		carveout.end = res.end,
+
+		ret = fdtdec_add_reserved_memory(new_blob, "tf-a", &carveout,
+						 NULL, 0, NULL,
+						 FDTDEC_RESERVED_MEMORY_NO_MAP);
+		if (ret < 0)
+			return ret;
+	}
+#endif
+
+	return 0;
+}
+
 #ifdef CONFIG_FMAN_ENET
 __weak int fdt_update_ethernet_dt(void *blob)
 {
@@ -56,6 +104,13 @@ int arch_fixup_fdt(void *blob)
 		return ret;
 #endif
 
+	ret = tfa_copy_reserved_memory(blob);
+	if (ret) {
+		printf("ERROR: transfer of TF-A nodes to new fdt failed: %s\n",
+		       fdt_strerror(ret));
+		return ret;
+	}
+
 #ifdef CONFIG_ARMV8_SPIN_TABLE
 	ret = spin_table_update_dt(blob);
 	if (ret)
-- 
2.54.0