x86: fsp: Mark memory used by U-Boot as reserved in the E820 table for S3

U-Boot itself as well as everything that is consumed by U-Boot (like
heap, stack, dtb, etc) needs to be reserved and reported in the E820
table when S3 resume is on.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>

arch/x86/Kconfig

@@ -601,6 +601,14 @@ config HAVE_ACPI_RESUME
 	  is done, U-Boot needs to find out the wakeup vector provided by OSes
 	  and jump there.
 
+config STACK_SIZE
+	hex
+	depends on HAVE_ACPI_RESUME
+	default 0x1000
+	help
+	  Estimated U-Boot's runtime stack size that needs to be reserved
+	  during an ACPI S3 resume.
+
 config MAX_PIRQ_LINKS
 	int
 	default 8

arch/x86/lib/fsp/fsp_dram.c

@@ -92,5 +92,17 @@ unsigned install_e820_map(unsigned max_entries, struct e820entry *entries)
 	entries[num_entries].type = E820_RESERVED;
 	num_entries++;
 
+#ifdef CONFIG_HAVE_ACPI_RESUME
+	/*
+	 * Everything between U-Boot's stack and ram top needs to be
+	 * reserved in order for ACPI S3 resume to work.
+	 */
+	entries[num_entries].addr = gd->start_addr_sp - CONFIG_STACK_SIZE;
+	entries[num_entries].size = gd->ram_top - gd->start_addr_sp + \
+		CONFIG_STACK_SIZE;
+	entries[num_entries].type = E820_RESERVED;
+	num_entries++;
+#endif
+
 	return num_entries;
 }