Add support for parsing the "linux,usable-memory-range" property in the
"/chosen" node to the FDT core code. This can co-exist safely with the
architecture-specific parsing, until the latter has been removed.
Architecture-specific code still has to make sure the resulting memory
range limitation is applied, if present.
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
About the change to chosen.txt: I have a similar change for
schemas/chosen.yaml in dt-schema.
v4:
- New.
---
Documentation/devicetree/bindings/chosen.txt | 6 ++---
drivers/of/fdt.c | 24 ++++++++++++++++++++
2 files changed, 27 insertions(+), 3 deletions(-)
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
index 5b0b94eb2d04e79d..1cc3aa10dcb10588 100644
--- a/Documentation/devicetree/bindings/chosen.txt
+++ b/Documentation/devicetree/bindings/chosen.txt
@@ -79,9 +79,9 @@ a different secondary CPU release mechanism)
linux,usable-memory-range
-------------------------
-This property (arm64 only) 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.
+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.
This property describes a limitation: memory within this range is only
valid when also described through another mechanism that the kernel
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index f797d52c5b492cb7..1b4dd5418b44b9fb 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -935,6 +935,29 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
elfcorehdr_addr, elfcorehdr_size);
}
+/**
+ * early_init_dt_check_for_usable_mem_range - Decode usable memory range
+ * location from flat tree
+ * @node: reference to node containing usable memory range location ('chosen')
+ */
+static void __init early_init_dt_check_for_usable_mem_range(unsigned long node)
+{
+ const __be32 *prop;
+ int len;
+
+ pr_debug("Looking for usable-memory-range property... ");
+
+ prop = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
+ if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
+ return;
+
+ cap_mem_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
+ cap_mem_size = dt_mem_next_cell(dt_root_size_cells, &prop);
+
+ pr_debug("cap_mem_start=%pa cap_mem_size=%pa\n", &cap_mem_addr,
+ &cap_mem_size);
+}
+
#ifdef CONFIG_SERIAL_EARLYCON
int __init early_init_dt_scan_chosen_stdout(void)
@@ -1083,6 +1106,7 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
early_init_dt_check_for_initrd(node);
early_init_dt_check_for_elfcorehdr(node);
+ early_init_dt_check_for_usable_mem_range(node);
/* Retrieve command line */
p = of_get_flat_dt_prop(node, "bootargs", &l);
--
2.25.1
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