x86: Add a way to add to the e820 memory table

Some boards want to reserve extra regions of memory. Add a 'chosen'
property to support this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/lib/fsp/fsp_dram.c b/arch/x86/lib/fsp/fsp_dram.c
index faa819f..a76497d 100644
--- a/arch/x86/lib/fsp/fsp_dram.c
+++ b/arch/x86/lib/fsp/fsp_dram.c
@@ -12,6 +12,7 @@
 #include <asm/mrccache.h>
 #include <asm/mtrr.h>
 #include <asm/post.h>
+#include <dm/ofnode.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -92,6 +93,8 @@
 	unsigned int num_entries = 0;
 	const struct hob_header *hdr;
 	struct hob_res_desc *res_desc;
+	const fdt64_t *prop;
+	int size;
 
 	hdr = gd->arch.hob_list;
 
@@ -133,6 +136,20 @@
 		num_entries++;
 	}
 
+	prop = ofnode_read_chosen_prop("e820-entries", &size);
+	if (prop) {
+		int count = size / (sizeof(u64) * 3);
+		int i;
+
+		if (num_entries + count >= max_entries)
+			return -ENOSPC;
+		for (i = 0; i < count; i++, num_entries++, prop += 3) {
+			entries[num_entries].addr = fdt64_to_cpu(prop[0]);
+			entries[num_entries].size = fdt64_to_cpu(prop[1]);
+			entries[num_entries].type = fdt64_to_cpu(prop[2]);
+		}
+	}
+
 	return num_entries;
 }
 
diff --git a/doc/device-tree-bindings/chosen.txt b/doc/device-tree-bindings/chosen.txt
index d4dfc05..e5ba672 100644
--- a/doc/device-tree-bindings/chosen.txt
+++ b/doc/device-tree-bindings/chosen.txt
@@ -143,3 +143,21 @@
 node to add. The ACPI information is written in this order.
 
 If the ordering does not include all nodes, an error is generated.
+
+e820-entries
+------------
+
+This provides a way to add entries to the e820 table which tells the OS about
+the memory map. The property contains three sets of 64-bit values:
+
+   address   - Start address of region
+   size      - Size of region
+   flags     - Flags (E820_...)
+
+Example:
+
+chosen {
+	e820-entries = /bits/ 64 <
+		IOMAP_P2SB_BAR IOMAP P2SB_SIZE E820_RESERVED
+		MCH_BASE_ADDRESS     MCH_SIZE  E820_RESERVED>;
+};