[PATCH v2] lib: utils: fdt: fix "ranges" translation

[Max Hsu]

According to the Device Tree Spec, Chapter 2.3.8 "ranges" [1]:
The parent address size will be determined from the #address-cells
property of the node that defines the parent’s address space.

In fdt_translate_address(), which considered the parent address size
is the child address size, this commit fix the two address sizes
and parsing the address independently.

Signed-off-by: Max Hsu <max.hsu at sifive.com>
---
v1 fix will introduce another bug in the following case.

The node in DTS depth 1 if execute fdt_get_node_addr_size(), inside
the function, the fdt_translate_address() will try to get the child
"#address-cells" and "#size-cells" in DTS depth 0, and the parent
"#address-cells" in DTS depth -1. which will cause early abort.
With fdt_translate_address() early abort, the parameter "addr" didn't
got any assignment of the address value. This let
fdt_get_node_addr_size() return with unknown value of parameter "addr".

For the v2 fix, which will check the "ranges" first, since the above
case shouldn't happen in the DTS as the "ranges" should be existed in
DTS depth more than 0. This fix also improve execution cycle. 
---
Changes in v2:
- fix v1 bug mentioned in the cover letter.
- Link to v1: https://lore.kernel.org/r/20250708-dev-maxh-master_fdt_helper-v1-1-866c165f1f85@sifive.com
---
 lib/utils/fdt/fdt_helper.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
index 0f4859c1a721bc7c2871bacefe27caba7780f752..799fd48dc3abf0a3c1963f84dd6bde271e6c08d7 100644
--- a/lib/utils/fdt/fdt_helper.c
+++ b/lib/utils/fdt/fdt_helper.c
@@ -84,23 +84,27 @@ static int fdt_translate_address(const void *fdt, uint64_t reg, int parent,
 				 uint64_t *addr)
 {
 	int i, rlen;
-	int cell_addr, cell_size;
+	int cell_parent_addr, cell_child_addr, cell_size;
 	const fdt32_t *ranges;
 	uint64_t offset, caddr = 0, paddr = 0, rsize = 0;
 
-	cell_addr = fdt_address_cells(fdt, parent);
-	if (cell_addr < 1)
-		return SBI_ENODEV;
-
-	cell_size = fdt_size_cells(fdt, parent);
-	if (cell_size < 0)
-		return SBI_ENODEV;
-
 	ranges = fdt_getprop(fdt, parent, "ranges", &rlen);
 	if (ranges && rlen > 0) {
-		for (i = 0; i < cell_addr; i++)
+		cell_child_addr = fdt_address_cells(fdt, parent);
+		if (cell_child_addr < 1)
+			return SBI_ENODEV;
+
+		cell_parent_addr = fdt_address_cells(fdt, fdt_parent_offset(fdt, parent));
+		if (cell_parent_addr < 1)
+			return SBI_ENODEV;
+
+		cell_size = fdt_size_cells(fdt, parent);
+		if (cell_size < 0)
+			return SBI_ENODEV;
+
+		for (i = 0; i < cell_child_addr; i++)
 			caddr = (caddr << 32) | fdt32_to_cpu(*ranges++);
-		for (i = 0; i < cell_addr; i++)
+		for (i = 0; i < cell_parent_addr; i++)
 			paddr = (paddr << 32) | fdt32_to_cpu(*ranges++);
 		for (i = 0; i < cell_size; i++)
 			rsize = (rsize << 32) | fdt32_to_cpu(*ranges++);

---
base-commit: a32a91069119e7a5aa31e6bc51d5e00860be3d80
change-id: 20250708-dev-maxh-master_fdt_helper-46d2eeeb07cd

Best regards,
-- 
Max Hsu <max.hsu at sifive.com>