sunxi: (mksunxiboot) signature to indicate "sunxi" SPL variant
This patch follows up on a discussion of ways to improve support
for the sunxi FEL ("USB boot") mechanism, especially with regard
to boot scripts, see:
https://groups.google.com/d/msg/linux-sunxi/wBEGUoLNRro/rHGq6nSYCQAJ
The idea is to convert the (currently unused) "pad" bytes in the
SPL header into an area where data can be passed to U-Boot. To
do this safely, we have to make sure that we're actually using
our "sunxi" flavor of the SPL, and not the Allwinner boot0.
The modified mksunxiboot introduces a special signature to the
SPL header in place of the "pub_head_size" field. This can be
used to reliably distinguish between compatible versions of sunxi
SPL and anything else (older variants or Allwinner's boot0).
Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/arch/arm/include/asm/arch-sunxi/spl.h b/arch/arm/include/asm/arch-sunxi/spl.h
index 5bcd0eb..d2ce848 100644
--- a/arch/arm/include/asm/arch-sunxi/spl.h
+++ b/arch/arm/include/asm/arch-sunxi/spl.h
@@ -9,6 +9,8 @@
#define _ASM_ARCH_SPL_H_
#define BOOT0_MAGIC "eGON.BT0"
+#define SPL_SIGNATURE "SPL" /* marks "sunxi" SPL header */
+#define SPL_HEADER_VERSION 1
/* boot head definition from sun4i boot code */
struct boot_file_head {
@@ -21,8 +23,23 @@
* by the boot ROM. To be compatible with Allwinner tools we
* would need to implement the proper fields here instead of
* padding.
+ *
+ * Actually we want the ability to recognize our "sunxi" variant
+ * of the SPL. To do so, let's place a special signature into the
+ * "pub_head_size" field. We can reasonably expect Allwinner's
+ * boot0 to always have the upper 16 bits of this set to 0 (after
+ * all the value shouldn't be larger than the limit imposed by
+ * SRAM size).
+ * If the signature is present (at 0x14), then we know it's safe
+ * to use the remaining 8 bytes (at 0x18) for our own purposes.
+ * (E.g. sunxi-tools "fel" utility can pass information there.)
*/
- uint8_t pad[12]; /* align to 32 bytes */
+ union {
+ uint32_t pub_head_size;
+ uint8_t spl_signature[4];
+ };
+ uint32_t fel_script_address;
+ uint32_t reserved; /* padding, align to 32 bytes */
};
#endif