x86: Set up the MTRR for SDRAM

Set up MTRRs for the FSP SDRAM regions to improve performance.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

arch/x86/lib/fsp/fsp_dram.c

@@ -9,6 +9,7 @@
 #include <asm/fsp/fsp_support.h>
 #include <asm/e820.h>
 #include <asm/mrccache.h>
+#include <asm/mtrr.h>
 #include <asm/post.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -61,6 +62,8 @@ int dram_init_banksize(void)
 
 		gd->bd->bi_dram[bank].start = res_desc->phys_start;
 		gd->bd->bi_dram[bank].size = res_desc->len;
+		mtrr_add_request(MTRR_TYPE_WRBACK, res_desc->phys_start,
+				 res_desc->len);
 		log_debug("ram %llx %llx\n", gd->bd->bi_dram[bank].start,
 			  gd->bd->bi_dram[bank].size);
 	}
@@ -69,6 +72,8 @@ int dram_init_banksize(void)
 	gd->bd->bi_dram[0].start = 0;
 	gd->bd->bi_dram[0].size = low_end;
 
+	mtrr_add_request(MTRR_TYPE_WRBACK, 0, low_end);
+
 	return 0;
 }