[PATCH 05/11] of: reserved_mem: add linux,no-dump property support for reserved memory regions

[Chen Wandun]

Add a 'no_dump' field to struct reserved_mem and parse the
'linux,no-dump' device tree property during reserved memory node
initialization. This property allows device tree authors to mark
specific reserved memory regions that should be excluded from kdump
vmcore dumps.

Reserved memory regions used by device firmware (e.g., GPU, DSP, modem)
typically contain data that is not useful for kernel crash analysis and
can significantly increase vmcore size. The 'linux,no-dump' property
provides a declarative way to indicate these regions should be filtered
out when constructing the elfcorehdr for kdump.

The property is named with a 'linux,' prefix because kdump/vmcore is
Linux-specific and the property is an OS hint rather than a hardware
description, matching existing properties such as 'linux,cma-default'
and 'linux,usable-memory-range'.

The 'linux,no-dump' property is only effective when the region:
 - Does not have 'no-map': these regions are already excluded from
   vmcore since they are removed from the linear mapping (MEMBLOCK_NOMAP).
 - Does not have 'reusable': CMA reusable regions are actively used by
   the kernel for movable page allocations, and their contents are
   valuable for crash analysis.

The no-dump status is also printed in the boot log alongside the
existing nomap and reusable flags for diagnostic purposes.

Corresponding dt-schema binding update:
  https://github.com/devicetree-org/dt-schema/pull/193

Signed-off-by: Chen Wandun <chenwandun at lixiang.com>
Tested-by: Zhao Meijing <zhaomeijing at lixiang.com>
---
 drivers/of/of_reserved_mem.c    | 13 ++++++++-----
 include/linux/of_reserved_mem.h |  1 +
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 93585af9f8a3..ac3d8b837d61 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -654,6 +654,7 @@ static void __init fdt_init_reserved_mem_node(unsigned long node, const char *un
 {
 	int err = 0;
 	bool nomap;
+	bool reusable;
 
 	struct reserved_mem *rmem = &reserved_mem[reserved_mem_count];
 
@@ -662,11 +663,14 @@ static void __init fdt_init_reserved_mem_node(unsigned long node, const char *un
 		return;
 	}
 
+	nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
+	reusable = of_get_flat_dt_prop(node, "reusable", NULL) != NULL;
+
 	rmem->name = uname;
 	rmem->base = base;
 	rmem->size = size;
-
-	nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
+	rmem->no_dump = !nomap && !reusable &&
+			of_get_flat_dt_prop(node, "linux,no-dump", NULL) != NULL;
 
 	err = __reserved_mem_init_node(rmem, node);
 	if (err != 0 && err != -ENODEV) {
@@ -680,13 +684,12 @@ static void __init fdt_init_reserved_mem_node(unsigned long node, const char *un
 		return;
 	} else {
 		phys_addr_t end = rmem->base + rmem->size - 1;
-		bool reusable =
-			(of_get_flat_dt_prop(node, "reusable", NULL)) != NULL;
 
-		pr_info("%pa..%pa (%lu KiB) %s %s %s\n",
+		pr_info("%pa..%pa (%lu KiB) %s %s %s %s\n",
 			&rmem->base, &end, (unsigned long)(rmem->size / SZ_1K),
 			nomap ? "nomap" : "map",
 			reusable ? "reusable" : "non-reusable",
+			rmem->no_dump ? "no-dump" : "dump",
 			rmem->name ? rmem->name : "unknown");
 	}
 
diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
index e8b20b29fa68..29674f572673 100644
--- a/include/linux/of_reserved_mem.h
+++ b/include/linux/of_reserved_mem.h
@@ -15,6 +15,7 @@ struct reserved_mem {
 	phys_addr_t			base;
 	phys_addr_t			size;
 	void				*priv;
+	bool				no_dump;
 };
 
 struct reserved_mem_ops {
-- 
2.43.0