intel/lynxpoint: Allow building without IFD (descripter.bin)

On newer Intel systems, like Intel Lynx Point, the flash ROM is shared
between the host processor (BIOS), its Management Engine (ME) and an
integrated Ethernet controller (GbE). The layout of the flash ROM (and
other information) is kept in the so called Intel Firmware Descriptor
(IFD).  If we only want to build coreboot to update the BIOS section,
all we need is the flash layout.

So add the option to specify the flash layout in the mainboard’s
Kconfig, and thus, to build without the real IFD. However, with such a
build, one has to make sure that the IFD section on the flash ROM will
not be written over (nor any other section that has not been included
by coreboot). A patch to write selected sections of a flash ROM with
IFD has been sent to the flashrom mailing list [2].

The same was done in commit a15cd66b [1] (sandybridge: Make build
possible without descriptor.bin) for Intel Sandy Bridge (BD82x6x).

[1] http://www.flashrom.org/pipermail/flashrom/2013-June/011083.html
    [PATCH] Add option to read ROM layout from IFD
[2] http://review.coreboot.org/3524

Change-Id: I26a604446cdf37a6bbcee2b14a107b7ccf417d5c
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/6046
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/southbridge/intel/lynxpoint/Kconfig

@@ -54,6 +54,52 @@ config SERIRQ_CONTINUOUS_MODE
 	  If you set this option to y, the serial IRQ machine will be
 	  operated in continuous mode.
 
+config HAVE_IFD_BIN
+	bool
+	default y
+
+config BUILD_WITH_FAKE_IFD
+	bool "Build with a fake IFD"
+	default y if !HAVE_IFD_BIN
+	help
+	  If you don't have an Intel Firmware Descriptor (ifd.bin) for your
+	  board, you can select this option and coreboot will build without it.
+	  Though, the resulting coreboot.rom will not contain all parts required
+	  to get coreboot running on your board. You can however write only the
+	  BIOS section to your board's flash ROM and keep the other sections
+	  untouched. Unfortunately the current version of flashrom doesn't
+	  support this yet. But there is a patch pending [1].
+
+	  WARNING: Never write a complete coreboot.rom to your flash ROM if it
+		   was built with a fake IFD. It just won't work.
+
+          [1] http://www.flashrom.org/pipermail/flashrom/2013-June/011083.html
+
+config IFD_BIOS_SECTION
+	depends on BUILD_WITH_FAKE_IFD
+	string
+	default ""
+
+config IFD_ME_SECTION
+	depends on BUILD_WITH_FAKE_IFD
+	string
+	default ""
+
+config IFD_GBE_SECTION
+	depends on BUILD_WITH_FAKE_IFD
+	string
+	default ""
+
+config IFD_PLATFORM_SECTION
+	depends on BUILD_WITH_FAKE_IFD
+	string
+	default ""
+
+config IFD_BIN_PATH
+	string "Path to intel firmware descriptor"
+	depends on !BUILD_WITH_FAKE_IFD
+	default "3rdparty/mainboard/$(MAINBOARDDIR)/descriptor.bin"
+
 config ME_BIN_PATH
 	string "Path to management engine firmware"
 	default "3rdparty/mainboard/$(MAINBOARDDIR)/me.bin"

src/southbridge/intel/lynxpoint/Makefile.inc

@@ -63,9 +63,27 @@ ramstage-y += gpio.c
 smm-$(CONFIG_HAVE_SMI_HANDLER) += gpio.c
 endif
 
-lynxpoint_add_me: $(obj)/coreboot.pre $(IFDTOOL)
+ifeq ($(CONFIG_BUILD_WITH_FAKE_IFD),y)
+IFD_BIN_PATH := $(objgenerated)/ifdfake.bin
+IFD_SECTIONS := $(addprefix -b ,$(CONFIG_IFD_BIOS_SECTION:"%"=%)) \
+		$(addprefix -m ,$(CONFIG_IFD_ME_SECTION:"%"=%)) \
+		$(addprefix -g ,$(CONFIG_IFD_GBE_SECTION:"%"=%)) \
+		$(addprefix -p ,$(CONFIG_IFD_PLATFORM_SECTION:"%"=%))
+else
+IFD_BIN_PATH := $(CONFIG_IFD_BIN_PATH)
+endif
+
+lynxpoint_add_me: $(obj)/coreboot.pre $(IFDTOOL) $(IFDFAKE)
+ifeq ($(CONFIG_BUILD_WITH_FAKE_IFD),y)
+	printf "\n** WARNING **\n"
+	printf "Coreboot will be built with a fake Intel Firmware Descriptor (IFD).\n"
+	printf "Never write a complete coreboot.rom with a fake IFD to your board's\n"
+	printf "flash ROM! Make sure that you only write valid flash regions.\n\n"
+	printf "    IFDFAKE    Building a fake Intel Firmware Descriptor\n"
+	$(IFDFAKE) $(IFD_SECTIONS) $(IFD_BIN_PATH)
+endif
 	printf "    DD         Adding Intel Firmware Descriptor\n"
-	dd if=$(CONFIG_IFD_BIN_PATH) \
+	dd if=$(IFD_BIN_PATH) \
 		of=$(obj)/coreboot.pre conv=notrunc >/dev/null 2>&1
 	printf "    IFDTOOL    me.bin -> coreboot.pre\n"
 	$(objutil)/ifdtool/ifdtool \
@@ -76,7 +94,7 @@ ifeq ($(CONFIG_LOCK_MANAGEMENT_ENGINE),y)
 	printf "    IFDTOOL    Locking Management Engine\n"
 	$(objutil)/ifdtool/ifdtool -l $(obj)/coreboot.pre
 	mv $(obj)/coreboot.pre.new $(obj)/coreboot.pre
-else
+else ifneq ($(CONFIG_BUILD_WITH_FAKE_IFD),y)
 	printf "    IFDTOOL    Unlocking Management Engine\n"
 	$(objutil)/ifdtool/ifdtool -u $(obj)/coreboot.pre
 	mv $(obj)/coreboot.pre.new $(obj)/coreboot.pre