[U-Boot] [RFC PATCH 1/3] sunxi: Extend SPL header versioning

[Andre Przywara]

On Allwinner SoCs we use some free bytes at the beginning of the SPL image
to store various information. We have a version byte to allow updates,
but changing this always requires all tools to be updated as well.

Introduce the concept of semantic versioning [1] to the SPL header:
The major part of the version number only changes on incompatible
updates, a minor number bump indicates backward compatibility.
This patch just documents the major/minor split, adds some comments
to the header file and uses the versioning information for the existing
users.

[1] https://semver.org

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 arch/arm/include/asm/arch-sunxi/spl.h | 19 ++++++++++++++-----
 board/sunxi/board.c                   |  4 ++--
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/arch-sunxi/spl.h b/arch/arm/include/asm/arch-sunxi/spl.h
index 4277d836e5..7cf89c8db2 100644
--- a/arch/arm/include/asm/arch-sunxi/spl.h
+++ b/arch/arm/include/asm/arch-sunxi/spl.h
@@ -9,7 +9,16 @@
 
 #define BOOT0_MAGIC		"eGON.BT0"
 #define SPL_SIGNATURE		"SPL" /* marks "sunxi" SPL header */
-#define SPL_HEADER_VERSION	2
+#define SPL_MAJOR_BITS		3
+#define SPL_MINOR_BITS		5
+#define SPL_VERSION(maj, min)						\
+	((((maj) & ((1U << SPL_MAJOR_BITS) - 1)) << SPL_MINOR_BITS) | \
+	((min) & ((1U << SPL_MINOR_BITS) - 1)))
+
+#define SPL_HEADER_VERSION	SPL_VERSION(0, 2)
+
+#define SPL_ENV_HEADER_VERSION	SPL_VERSION(0, 1)
+#define SPL_DT_HEADER_VERSION	SPL_VERSION(0, 2)
 
 #ifdef CONFIG_SUNXI_HIGH_SRAM
 #define SPL_ADDR		0x10000
@@ -49,14 +58,14 @@ struct boot_file_head {
 		uint32_t pub_head_size;
 		uint8_t spl_signature[4];
 	};
-	uint32_t fel_script_address;
+	uint32_t fel_script_address;	/* since v0.1, set by sunxi-fel */
 	/*
 	 * If the fel_uEnv_length member below is set to a non-zero value,
 	 * it specifies the size (byte count) of data at fel_script_address.
 	 * At the same time this indicates that the data is in uEnv.txt
 	 * compatible format, ready to be imported via "env import -t".
 	 */
-	uint32_t fel_uEnv_length;
+	uint32_t fel_uEnv_length;	/* since v0.1, set by sunxi-fel */
 	/*
 	 * Offset of an ASCIIZ string (relative to the SPL header), which
 	 * contains the default device tree name (CONFIG_DEFAULT_DEVICE_TREE).
@@ -64,11 +73,11 @@ struct boot_file_head {
 	 * by flash programming tools for providing nice informative messages
 	 * to the users.
 	 */
-	uint32_t dt_name_offset;
+	uint32_t dt_name_offset;	/* since v0.2, set by mksunxiboot */
 	uint32_t reserved1;
 	uint32_t boot_media;		/* written here by the boot ROM */
 	/* A padding area (may be used for storing text strings) */
-	uint32_t string_pool[13];
+	uint32_t string_pool[13];	/* since v0.2, filled by mksunxiboot */
 	/* The header must be a multiple of 32 bytes (for VBAR alignment) */
 };
 
diff --git a/board/sunxi/board.c b/board/sunxi/board.c
index 3d364c6db5..a105d0a5ab 100644
--- a/board/sunxi/board.c
+++ b/board/sunxi/board.c
@@ -631,9 +631,9 @@ static void parse_spl_header(const uint32_t spl_addr)
 		return; /* signature mismatch, no usable header */
 
 	uint8_t spl_header_version = spl->spl_signature[3];
-	if (spl_header_version != SPL_HEADER_VERSION) {
+	if (spl_header_version < SPL_ENV_HEADER_VERSION) {
 		printf("sunxi SPL version mismatch: expected %u, got %u\n",
-		       SPL_HEADER_VERSION, spl_header_version);
+		       SPL_ENV_HEADER_VERSION, spl_header_version);
 		return;
 	}
 	if (!spl->fel_script_address)
-- 
2.14.1