[PATCH v2 3/4] mkimage: sunxi_egon: add support for riscv

[Icenowy Zheng <icenowy@aosc.io>]

There's now a sun20i family in sunxi, which uses RISC-V CPU.

Add support for making eGON.BT0 image for RISC-V.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
---
Changes in v2:
- Removed changes that should belong to the previous patch in v1.

 tools/sunxi_egon.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tools/sunxi_egon.c b/tools/sunxi_egon.c
index 062c9bc151..836e99a6e6 100644
--- a/tools/sunxi_egon.c
+++ b/tools/sunxi_egon.c
@@ -29,6 +29,7 @@ static int egon_check_params(struct image_tool_params *params)
 	 */
 	switch (arch) {
 	case IH_ARCH_ARM:
+	case IH_ARCH_RISCV:
 		break;
 	default:
 		return EXIT_FAILURE;
@@ -60,6 +61,10 @@ static int egon_verify_header(unsigned char *ptr, int image_size,
 		if ((le32_to_cpu(header->b_instruction) & 0xff000000) != 0xea000000)
 			return EXIT_FAILURE;
 		break;
+	case IH_ARCH_RISCV:
+		if ((le32_to_cpu(header->b_instruction) & 0x00000fff) != 0x0000006f)
+			return EXIT_FAILURE;
+		break;
 	default:
 		return EXIT_FAILURE; /* Unknown architecture */
 	}
@@ -128,6 +133,24 @@ static void egon_set_header(void *buf, struct stat *sbuf, int infd,
 		value = 0xea000000 | (sizeof(struct boot_file_head) / 4 - 2);
 		header->b_instruction = cpu_to_le32(value);
 		break;
+	case IH_ARCH_RISCV:
+		/*
+		 * Generate a RISC-V JAL instruction with rd=x0
+		 * (pseudo instruction J, jump without side effects).
+		 *
+		 * The following weird bit operation maps imm[20]
+		 * to inst[31], imm[10:1] to inst[30:21],
+		 * imm[11] to inst[20], imm[19:12] to inst[19:12],
+		 * and imm[0] is dropped (because 1-byte RISC-V instruction
+		 * is not allowed).
+		 */
+		value = 0x0000006f |
+			((sizeof(struct boot_file_head) & 0x00100000) << 11) |
+			((sizeof(struct boot_file_head) & 0x000007fe) << 20) |
+			((sizeof(struct boot_file_head) & 0x00000800) << 9) |
+			((sizeof(struct boot_file_head) & 0x000ff000) << 0);
+		header->b_instruction = cpu_to_le32(value);
+		break;
 	}
 
 	memcpy(header->magic, BOOT0_MAGIC, sizeof(header->magic));
-- 
2.30.2