riscv: boot: add zstd support

Support build the zstd compressed Image.zst. Similar as other
compressed formats, the Image.zst is not self-decompressing and
the bootloader still needs to handle decompression before
launching the kernel image.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20221123150257.3108-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index d1a49ad..c72de72 100644 (file)
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -56,6 +56,9 @@ $(obj)/Image.lzma: $(obj)/Image FORCE
 $(obj)/Image.lzo: $(obj)/Image FORCE
        $(call if_changed,lzo)
 
+$(obj)/Image.zst: $(obj)/Image FORCE
+       $(call if_changed,zstd)
+
 $(obj)/loader.bin: $(obj)/loader FORCE
        $(call if_changed,objcopy)