x86/of: Unconditionally call unflatten_and_copy_device_tree()

Call this function unconditionally so that we can populate an empty DTB
on platforms that don't boot with a firmware provided or builtin DTB.
There's no harm in calling unflatten_device_tree() unconditionally here.
If there isn't a non-NULL 'initial_boot_params' pointer then
unflatten_device_tree() returns early.

Cc: Rob Herring <[email protected]>
Cc: Frank Rowand <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: H. Peter Anvin <[email protected]>
Tested-by: Saurabh Sengar <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rob Herring <[email protected]>

Author: bebarino

arch/x86/kernel/devicetree.c

@@ -283,22 +283,24 @@ void __init x86_flattree_get_config(void)
 	u32 size, map_len;
 	void *dt;
 
-	if (!initial_dtb)
-		return;
-
-	map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
+	if (initial_dtb) {
+		map_len = max(PAGE_SIZE - (initial_dtb & ~PAGE_MASK), (u64)128);
+
+		dt = early_memremap(initial_dtb, map_len);
+		size = fdt_totalsize(dt);
+		if (map_len < size) {
+			early_memunmap(dt, map_len);
+			dt = early_memremap(initial_dtb, size);
+			map_len = size;
+		}
 
-	dt = early_memremap(initial_dtb, map_len);
-	size = fdt_totalsize(dt);
-	if (map_len < size) {
-		early_memunmap(dt, map_len);
-		dt = early_memremap(initial_dtb, size);
-		map_len = size;
+		early_init_dt_verify(dt);
 	}
 
-	early_init_dt_verify(dt);
 	unflatten_and_copy_device_tree();
-	early_memunmap(dt, map_len);
+
+	if (initial_dtb)
+		early_memunmap(dt, map_len);
 }
 #endif