boot/riscv-pk: add bootloader for RISC-V architecture

Add the RISC-V Proxy Kernel (pk) package which provides the Berkeley
Boot Loader for booting RISC-V kernel images.

Signed-off-by: Mark Corbin <mark.corbin@embecosm.com>
[Thomas:
 - fix prompt of option to be just "riscv-pk"
 - add blank line between help text and upstream URL in Config.in file
 - use $(INSTALL) instead of cp to install the generated image]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -1301,6 +1301,7 @@ F:	package/ratpoison/
 N:	Mark Corbin <mark.corbin@embecosm.com>
 F:	arch/arch.mk.riscv
 F:	arch/Config.in.riscv
+F:	boot/riscv-pk/
 
 N:	Markos Chandras <markos.chandras@imgtec.com>
 F:	package/harfbuzz/

boot/Config.in

@@ -13,6 +13,7 @@ source "boot/gummiboot/Config.in"
 source "boot/lpc32xxcdl/Config.in"
 source "boot/mv-ddr-marvell/Config.in"
 source "boot/mxs-bootlets/Config.in"
+source "boot/riscv-pk/Config.in"
 source "boot/s500-bootloader/Config.in"
 source "boot/syslinux/Config.in"
 source "boot/ts4800-mbrboot/Config.in"

boot/riscv-pk/Config.in

@@ -0,0 +1,14 @@
+comment "riscv-pk needs a Linux kernel to be built"
+	depends on BR2_riscv
+	depends on !BR2_LINUX_KERNEL
+
+config BR2_TARGET_RISCV_PK
+	bool "riscv-pk"
+	depends on BR2_riscv
+	depends on BR2_LINUX_KERNEL
+	help
+	  The RISC-V Proxy Kernel (pk) package contains the Berkeley
+	  Boot Loader (BBL) which has been designed to boot a Linux
+	  kernel on a RISC-V processor.
+
+	  https://github.com/riscv/riscv-pk.git

boot/riscv-pk/riscv-pk.mk

@@ -0,0 +1,32 @@
+################################################################################
+#
+# riscv-pk
+#
+################################################################################
+
+RISCV_PK_VERSION = 706cc77c369fd3e4734b5a6aa813d421347f1814
+RISCV_PK_SITE = git://github.com/riscv/riscv-pk.git
+RISCV_PK_LICENSE = BSD-3-Clause
+RISCV_PK_LICENSE_FILES = LICENSE
+RISCV_PK_DEPENDENCIES = linux
+RISCV_PK_SUBDIR = build
+RISCV_PK_INSTALL_IMAGES = YES
+
+define RISCV_PK_CONFIGURE_CMDS
+	mkdir -p $(@D)/build
+	(cd $(@D)/build; \
+		$(TARGET_CONFIGURE_OPTS) ../configure \
+		--host=$(GNU_TARGET_NAME) \
+		--with-payload=$(BINARIES_DIR)/vmlinux \
+	)
+endef
+
+define RISCV_PK_BUILD_CMDS
+	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/build bbl
+endef
+
+define RISCV_PK_INSTALL_IMAGES_CMDS
+	$(INSTALL) -D -m 0755 $(@D)/build/bbl $(BINARIES_DIR)/bbl
+endef
+
+$(eval $(generic-package))