[PATCH v2 1/2] common: fdt_support: add support for setting usable memory

[Igor Opaniuk <igor.opaniuk@gmail.com>]

From: Igor Opaniuk <igor.opaniuk@toradex.com>

Add support for setting linux,usable-memory property in the memory
node of device tree for the kernel [1].

This property holds a base address and size, describing a
limited region in which memory may be considered available for use by
the kernel. Memory outside of this range is not available for use.

[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/chosen.txt

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
---

 common/fdt_support.c  | 35 +++++++++++++++++++++++++++++++++++
 include/fdt_support.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/common/fdt_support.c b/common/fdt_support.c
index 6834399039..02cf5c6241 100644
--- a/common/fdt_support.c
+++ b/common/fdt_support.c
@@ -467,6 +467,41 @@ int fdt_fixup_memory_banks(void *blob, u64 start[], u64 size[], int banks)
 	}
 	return 0;
 }
+
+int fdt_set_usable_memory(void *blob, u64 start[], u64 size[], int areas)
+{
+	int err, nodeoffset;
+	int len;
+	u8 tmp[8 * 16]; /* Up to 64-bit address + 64-bit size */
+
+	if (areas > 8) {
+		printf("%s: num areas %d exceeds hardcoded limit %d\n",
+		       __func__, areas, 8);
+		return -1;
+	}
+
+	err = fdt_check_header(blob);
+	if (err < 0) {
+		printf("%s: %s\n", __func__, fdt_strerror(err));
+		return err;
+	}
+
+	/* find or create "/memory" node. */
+	nodeoffset = fdt_find_or_add_subnode(blob, 0, "memory");
+	if (nodeoffset < 0)
+		return nodeoffset;
+
+	len = fdt_pack_reg(blob, tmp, start, size, areas);
+
+	err = fdt_setprop(blob, nodeoffset, "linux,usable-memory", tmp, len);
+	if (err < 0) {
+		printf("WARNING: could not set %s %s.\n",
+		       "reg", fdt_strerror(err));
+		return err;
+	}
+
+	return 0;
+}
 #endif
 
 int fdt_fixup_memory(void *blob, u64 start, u64 size)
diff --git a/include/fdt_support.h b/include/fdt_support.h
index cefb2b2cce..2286ea7793 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -94,6 +94,7 @@ int fdt_fixup_memory(void *blob, u64 start, u64 size);
  */
 #ifdef CONFIG_ARCH_FIXUP_FDT_MEMORY
 int fdt_fixup_memory_banks(void *blob, u64 start[], u64 size[], int banks);
+int fdt_set_usable_memory(void *blob, u64 start[], u64 size[], int banks);
 #else
 static inline int fdt_fixup_memory_banks(void *blob, u64 start[], u64 size[],
 					 int banks)
-- 
2.17.1