[U-Boot] [RFC PATCH 07/13] arm: nexell: embed NSIH header

[Andre Przywara]

The primary boot loaders provided by the SoC vendor or derived from that
use an image format called "NSIH" to learn the load address and size of
the boot payload. This header occupies 512 bytes, but contains only a
few essential words of information.
Use the boot0 feature to prepend this header before the actual U-Boot
proper. We automatically fill it with the required information, also
add a branch instruction to be able to enter at the beginning of the
header.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 arch/arm/Kconfig                         |  1 +
 arch/arm/include/asm/arch-nexell/boot0.h | 35 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 arch/arm/include/asm/arch-nexell/boot0.h

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c11e3f1f85..b0f3ee7289 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -655,6 +655,7 @@ config ARCH_MX5
 config ARCH_NEXELL
 	bool "Nexell S5P support"
 	select ARM64
+	select ENABLE_ARM_SOC_BOOT0_HOOK
 
 config ARCH_QEMU
 	bool "QEMU Virtual Platform"
diff --git a/arch/arm/include/asm/arch-nexell/boot0.h b/arch/arm/include/asm/arch-nexell/boot0.h
new file mode 100644
index 0000000000..b2adb06b4c
--- /dev/null
+++ b/arch/arm/include/asm/arch-nexell/boot0.h
@@ -0,0 +1,35 @@
+/*
+ * Nexell NSIH header, to allow loading U-Boot from secondboot.
+ *
+ * Both the proprietary and the GPL version of the first stage boot loader
+ * look for this magic header to determine the size and load address of
+ * the payload (similar to the information in an U-Boot image header).
+ * Make them happy by providing the essential bits:
+ * 	@0x040:	device address: 0 for SDMMC
+ * 	@0x044:	load size
+ * 	@0x048:	load address
+ * 	@0x04c:	launch address (entry point)
+ * 	@0x1fc: "NSIH" magic
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifdef CONFIG_ARM64
+	b	reset				// jump over the header
+	.space	0x3c				// fast forward to 0x40
+#else
+_start:
+	ARM_VECTORS
+	.space	0x20			 	// fill up from 0x20 till 0x40
+#endif
+	.word	0				// device "address" (device ID)
+	.word	(_end - _start) + 32768		// binary size + space for .dtb
+	.word	CONFIG_SYS_TEXT_BASE		// load address
+	.word	CONFIG_SYS_TEXT_BASE		// launch address
+	.space	0x1ac				// fast forward till 0x1fc
+	.word	0x4849534e			// "NSIH" magic
+
+	// In case someone enters right after the header:
+#ifdef CONFIG_ARM64
+	b	reset
+#endif
-- 
2.14.1