Payloads: Add U-Boot as a coreboot-payload

- Add Kconfig and Makefile options to use U-Boot as a payload.
- Add Kconfig option for extra cbfstool command line arguments.
- Add Kconfig & Makefile option to load the payload as a flat binary.
- Add u-boot directory to .gitignore.

This is currently working for X-86 only.

Graphics worked in U-Boot correctly by initializing the VBIOS and
setting up a console mode.

Tested in QEMU and on Minnowboard Max.  Got into U-Boot, have not
booted an OS yet.

Change-Id: Ia122a4ad7cd7d96107c1552b0376c8106ca8fb92
Signed-off-by: Martin Roth <martinroth@google.com>
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/12714
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/external/U-Boot/Makefile.inc

@@ -0,0 +1,82 @@
+##
+## This file is part of the coreboot project.
+##
+## Copyright (C) 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.
+##
+
+# 2016-1 tag
+STABLE_COMMIT_ID=fa85e826c16b9ce1ad302a57e9c4b24db0d8b930
+
+TAG-$(CONFIG_UBOOT_MASTER)=origin/master
+TAG-$(CONFIG_UBOOT_STABLE)=$(STABLE_COMMIT_ID)
+
+project_name=U-Boot
+project_dir=u-boot
+project_git_repo=http://git.denx.de/u-boot.git
+project_config_file=$(project_dir)/.config
+
+unexport KCONFIG_AUTOHEADER
+unexport KCONFIG_AUTOCONFIG
+unexport KCONFIG_DEPENDENCIES
+unexport KCONFIG_SPLITCONFIG
+unexport KCONFIG_TRISTATE
+unexport KCONFIG_NEGATIVES
+
+all: build
+
+$(project_dir):
+	echo "    Cloning $(project_name) from Git"
+	git clone $(project_git_repo) $(project_dir)
+
+fetch: $(project_dir)
+ifeq ($(CONFIG_UBOOT_MASTER),y)
+	echo "    Fetching new commits from the $(project_name) git repo"
+	git fetch
+
+	#master doesn't get a file, so it's continuously updated
+	rm -f $(project_dir)/$(STABLE_COMMIT_ID)
+else
+	cd $(project_dir); git show $(TAG-y) >/dev/null 2>&1 ;	if [ $$? -ne 0 ]; \
+	then echo "    Fetching new commits from the $(project_name) git repo"; git fetch; fi
+	touch $(project_dir)/$(STABLE_COMMIT_ID)
+endif
+
+$(project_dir)/$(TAG-y): fetch
+	echo "    Checking out $(project_name) revision $(TAG-y)"
+	cd $(project_dir); git checkout master; git branch -D coreboot 2>/dev/null; git checkout -b coreboot $(TAG-y)
+
+config: $(project_dir)/$(TAG-y)
+	rm -f $(project_config_file)
+ifneq ($(CONFIG_PAYLOAD_CONFIGFILE),)
+ifneq ("$(wildcard $(CONFIG_PAYLOAD_CONFIGFILE))","")
+	cat $(CONFIG_PAYLOAD_CONFIGFILE)" > $(project_config_file)
+else
+	echo "Error: File $(CONFIG_PAYLOAD_CONFIGFILE) does not exist"
+	false
+endif
+else
+	cat $(project_dir)/configs/coreboot-x86_defconfig >> $(project_config_file)
+endif
+
+	$(MAKE) -C $(project_dir) olddefconfig
+
+build: config
+	echo "    MAKE       $(project_name) $(TAG-y)"
+	$(MAKE) -C $(project_dir)
+
+clean:
+	test -d $(project_dir) && $(MAKE) -C $(project_dir) clean || exit 0
+
+distclean:
+	rm -rf $(project_dir)
+
+.PHONY: config build clean distclean fetch