arm64: provide early SoC initialization

Some of the SoC's need an early hook to configure
certain registers. One example of this is on t132
where ramstage is the first thing being ran on the
arm64 core and it is the only entity that can configure
certain registers required for the rest of ramstage.
Therefore, provide the opportunity for the SoC to
implement such requirements.

BUG=chrome-os-partner:30572
BRANCH=None
TEST=Built and ran through coreboot.

Change-Id: Ib352f3788872f888581b398c9b394b7c4e54b02a
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/208061
Reviewed-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>

src/arch/arm64/Makefile.inc

@@ -49,6 +49,8 @@ bootblock-$(CONFIG_BOOTBLOCK_CONSOLE) += early_console.c
 bootblock-y += id.S
 $(obj)/arch/arm64/id.bootblock.o: $(obj)/build.h
 
+bootblock-y += c_entry.c
+bootblock-y += stage_entry.S
 bootblock-y += stages.c
 bootblock-y += eabi_compat.c
 
@@ -74,6 +76,8 @@ endif # CONFIG_ARCH_BOOTBLOCK_ARM64
 
 ifeq ($(CONFIG_ARCH_ROMSTAGE_ARM64),y)
 
+romstage-y += c_entry.c
+romstage-y += stage_entry.S
 romstage-y += stages.c
 romstage-y += div0.c
 romstage-$(CONFIG_EARLY_CONSOLE) += early_console.c
@@ -101,6 +105,7 @@ endif # CONFIG_ARCH_ROMSTAGE_ARM64
 
 ifeq ($(CONFIG_ARCH_RAMSTAGE_ARM64),y)
 
+ramstage-y += c_entry.c
 ramstage-y += stages.c
 ramstage-y += div0.c
 ramstage-y += cpu.c

src/arch/arm64/c_entry.c

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2014 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <arch/stages.h>
+
+void __attribute__((weak)) arm64_soc_init(void)
+{
+	/* Default weak implementation does nothing. */
+}
+
+void arm64_init(void)
+{
+	arm64_soc_init();
+	main();
+}

src/arch/arm64/include/arch/stages.h

@@ -26,4 +26,12 @@ void stage_entry(void);
 void stage_exit(void *);
 void jmp_to_elf_entry(void *entry, unsigned long buffer, unsigned long size);
 
+/* C entry point for all arm64 stages. */
+void arm64_init(void);
+
+/* This function is called upon intial entry of each stage. It is called prior
+ * to main(). That means all of the common infrastructure will most likely not
+ * be available to be used (such as console). */
+void arm64_soc_init(void);
+
 #endif

src/arch/arm64/stage_entry.S

@@ -61,7 +61,7 @@ ENTRY(arm64_el3_startup)
 	.stack:
 		.quad _estack
 	.entry:
-		.quad main
+		.quad arm64_init
 ENDPROC(arm64_el3_startup)
 .global arm64_el3_startup_end
 arm64_el3_startup_end: