boot/grub2: add RISC-V 64bit EFI support

Grub can be built as a RISC-V UEFI application since commit [1]. This
commit was first included in grub version 2.04.

This commit enables this support.

[1] https://git.savannah.gnu.org/gitweb/?p=grub.git;a=commitdiff;h=f1957dc8a3347278a095bc8f44197662559a8ba3

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

boot/grub2/Config.in

@@ -4,6 +4,7 @@ config BR2_TARGET_GRUB2_ARCH_SUPPORTS
 	default y if BR2_x86_64
 	default y if BR2_arm
 	default y if BR2_aarch64
+	default y if BR2_RISCV_64
 	depends on BR2_USE_MMU
 
 config BR2_TARGET_GRUB2
@@ -102,6 +103,15 @@ config BR2_TARGET_GRUB2_ARM64_EFI
 	  Aarch64 platform and you want to boot Grub 2 as an EFI
 	  application.
 
+config BR2_TARGET_GRUB2_RISCV64_EFI
+	bool "riscv64-efi"
+	depends on BR2_RISCV_64
+	select BR2_TARGET_GRUB2_HAS_EFI_BOOT
+	help
+	  Select this option if the platform you're targetting is a
+	  64bit RISC-V platform and you want to boot Grub 2 as an EFI
+	  application.
+
 if BR2_TARGET_GRUB2_HAS_LEGACY_BOOT
 
 comment "Options for the x86 legacy BIOS or ARM U-Boot support"

boot/grub2/grub2.mk

@@ -93,6 +93,15 @@ GRUB2_BUILTIN_CONFIG_arm64-efi = $(GRUB2_BUILTIN_CONFIG_EFI)
 GRUB2_BUILTIN_MODULES_arm64-efi = $(GRUB2_BUILTIN_MODULES_EFI)
 GRUB2_TUPLES-$(BR2_TARGET_GRUB2_ARM64_EFI) += arm64-efi
 
+GRUB2_IMAGE_riscv64-efi = $(BINARIES_DIR)/efi-part/EFI/BOOT/bootriscv64.efi
+GRUB2_CFG_riscv64-efi = $(BINARIES_DIR)/efi-part/EFI/BOOT/grub.cfg
+GRUB2_PREFIX_riscv64-efi = /EFI/BOOT
+GRUB2_TARGET_riscv64-efi = riscv64
+GRUB2_PLATFORM_riscv64-efi = efi
+GRUB2_BUILTIN_CONFIG_riscv64-efi = $(GRUB2_BUILTIN_CONFIG_EFI)
+GRUB2_BUILTIN_MODULES_riscv64-efi = $(GRUB2_BUILTIN_MODULES_EFI)
+GRUB2_TUPLES-$(BR2_TARGET_GRUB2_RISCV64_EFI) += riscv64-efi
+
 # Grub2 is kind of special: it considers CC, LD and so on to be the
 # tools to build the host programs and uses TARGET_CC, TARGET_CFLAGS,
 # TARGET_CPPFLAGS, TARGET_LDFLAGS to build the bootloader itself.