coreboot: add a place to choose romstage loader

Instead of always loading romstage from cbfs provide a
way, similar to ramstage and payload, for other
program loaders to intervene. For now, only the cbfs
loader is consulted.

TEST=Booted to end of ramstage on qemu-armv7

Change-Id: I87c3e2e566d7a0723e775aa427de58af745ecdd5
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9934
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <edward.ocallaghan@koparo.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/lib/loaders/Makefile.inc

@@ -18,6 +18,7 @@
 #
 
 bootblock-y += load_and_run_romstage.c
+bootblock-y += cbfs_romstage_loader.c
 romstage-y += cbfs_ramstage_loader.c
 romstage-y += load_and_run_ramstage.c
 ramstage-y += cbfs_payload_loader.c

src/lib/loaders/cbfs_romstage_loader.c

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 Google Inc.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc.
+ */
+
+#include <cbfs.h>
+#include <program_loading.h>
+
+static int cbfs_load_romstage(struct prog *romstage)
+{
+	return cbfs_load_prog_stage(CBFS_DEFAULT_MEDIA, romstage);
+}
+
+const struct prog_loader_ops cbfs_romstage_loader = {
+	.name = "CBFS",
+	.prepare = cbfs_load_romstage,
+};

src/lib/loaders/load_and_run_romstage.c

@@ -26,20 +26,38 @@
 #include <program_loading.h>
 #include <timestamp.h>
 
+extern const struct prog_loader_ops cbfs_romstage_loader;
+
+static const struct prog_loader_ops *loaders[] = {
+	&cbfs_romstage_loader,
+};
+
 void run_romstage(void)
 {
+	int i;
 	struct prog romstage = {
 		.name = CONFIG_CBFS_PREFIX "/romstage",
 		.type = PROG_ROMSTAGE,
 	};
 
+	for (i = 0; i < ARRAY_SIZE(loaders); i++) {
+		const struct prog_loader_ops *ops;
+
+		ops = loaders[i];
+
+		printk(BIOS_DEBUG, "Trying %s romstage loader.\n", ops->name);
+
 		timestamp_add_now(TS_START_COPYROM);
-	if (cbfs_load_prog_stage(CBFS_DEFAULT_MEDIA, &romstage) < 0) {
-		if (IS_ENABLED(CONFIG_BOOTBLOCK_CONSOLE))
-			die("Couldn't load romstage.\n");
-		halt();
-	}
+
+		if (ops->prepare(&romstage))
+			continue;
+
 		timestamp_add_now(TS_END_COPYROM);
 
 		prog_run(&romstage);
 	}
+
+	if (IS_ENABLED(CONFIG_BOOTBLOCK_CONSOLE))
+		die("Couldn't load romstage.\n");
+	halt();
+}