sifive/fu540: add empty sdram init and size functions

Change-Id: I65f900a3277bc8a4a83ebc8883d4a325bd690bf8
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/27438
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/soc/sifive/fu540/Makefile.inc

@@ -19,9 +19,11 @@ bootblock-y += bootblock.c
 
 romstage-y += uart.c
 romstage-y += media.c
+romstage-y += sdram.c
 
 ramstage-y += uart.c
 ramstage-y += media.c
+ramstage-y += sdram.c
 ramstage-y += cbmem.c
 
 CPPFLAGS_common += -Isrc/soc/sifive/fu540/include

src/soc/sifive/fu540/include/soc/sdram.h

@@ -0,0 +1,24 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Philipp Hug <philipp@hug.cx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __SOC_SIFIVE_FU540_SDRAM_H__
+#define __SOC_SIFIVE_FU540_SDRAM_H__
+
+#include <types.h>
+
+void sdram_init(void);
+size_t sdram_size_mb(void);
+
+#endif

src/soc/sifive/fu540/sdram.c

@@ -0,0 +1,33 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 Philipp Hug <philipp@hug.cx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <soc/sdram.h>
+
+void sdram_init(void)
+{
+	// TODO: implement
+}
+
+size_t sdram_size_mb(void)
+{
+	static size_t size_mb = 0;
+
+	if (!size_mb) {
+		// TODO: implement
+		size_mb = 8 * 1024;
+	}
+
+	return size_mb;
+}