payloads/external: add skiboot (for QEMU/Power9)

Add an option to build skiboot as a payload. This makes QEMU Power9
board simpler to use as skiboot is necessary anyway.

Change-Id: I0b49ea7464c97cc2ff0d5030629deed549851372
Signed-off-by: Igor Bagnucki <igor.bagnucki@3mdeb.com>
Signed-off-by: Krystian Hebel <krystian.hebel@3mdeb.com>
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58656
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>

payloads/external/.gitignore

@@ -8,3 +8,5 @@ tint/tint/
 U-Boot/u-boot/
 Memtest86Plus/memtest86plus/
 iPXE/ipxe/
+skiboot/skiboot
+skiboot/build

payloads/external/Makefile.inc

@@ -332,3 +332,10 @@ payloads/external/Yabits/uefi/build/uefi.elf yabits:
 
 payloads/external/BOOTBOOT/bootboot/dist/bootbootcb.elf:
 	$(MAKE) -C payloads/external/BOOTBOOT all
+
+# skiboot
+
+payloads/external/skiboot/build/skiboot.elf:
+	$(MAKE) -C payloads/external/skiboot all \
+		CONFIG_SKIBOOT_GIT_REPO=$(CONFIG_SKIBOOT_GIT_REPO) \
+		CONFIG_SKIBOOT_REVISION=$(CONFIG_SKIBOOT_REVISION)

payloads/external/skiboot/Kconfig

@@ -0,0 +1,21 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+if PAYLOAD_SKIBOOT
+
+config PAYLOAD_FILE
+	default "payloads/external/skiboot/build/skiboot.elf"
+
+config SKIBOOT_GIT_REPO
+	string "Git repository of skiboot payload"
+	default "https://github.com/open-power/skiboot"
+	help
+	  Git repository which will be used to clone skiboot.
+
+config SKIBOOT_REVISION
+	string "Revision of skiboot payload"
+	default "d93ddbd39b4eeac0bc11dacbdadea76df2996c13" if BOARD_EMULATION_QEMU_POWER9
+	help
+	  Revision, that skiboot repository will be checked out to, before building
+	  an image.
+
+endif # PAYLOAD_SKIBOOT

payloads/external/skiboot/Kconfig.name

@@ -0,0 +1,8 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+config PAYLOAD_SKIBOOT
+	bool "skiboot"
+	depends on ARCH_PPC64
+	help
+	  Select this option if you want to build a coreboot image
+	  with a skiboot payload.

payloads/external/skiboot/Makefile

@@ -0,0 +1,36 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+build_dir=$(CURDIR)/build
+skiboot_dir=$(CURDIR)/skiboot
+skiboot_git_repo=$(CONFIG_SKIBOOT_GIT_REPO)
+skiboot_revision=$(CONFIG_SKIBOOT_REVISION)
+skiboot_elf=$(build_dir)/skiboot.elf
+skiboot_cross=$(or $(CROSS),powerpc64-linux-gnu-)
+
+unexport $(COREBOOT_EXPORTS)
+
+.PHONY: all clean distclean
+
+all: $(skiboot_elf)
+
+$(skiboot_elf): | $(skiboot_dir) $(build_dir)
+	+$(MAKE) -C $(skiboot_dir) CROSS="$(skiboot_cross)"
+	cp $(skiboot_dir)/skiboot.elf $@
+	# skiboot is always built with debug information due to unconditional -ggdb
+	$(skiboot_cross)strip $@
+
+$(skiboot_dir):
+	git clone $(skiboot_git_repo) $(skiboot_dir)
+	git -C $(skiboot_dir) checkout $(skiboot_revision)
+
+$(build_dir):
+	mkdir -p $(build_dir)
+
+distclean: clean
+	rm -rf $(skiboot_dir)
+
+clean:
+	# Redefine RM because it's used like `$(RM) non-existent-file`
+	# Also ignore useless messages about removing test files
+	[ ! -d $(skiboot_dir) ] || $(MAKE) -C $(skiboot_dir) RM="rm -rf" clean > /dev/null
+	rm -rf $(build_dir)