[U-Boot] [PATCH v3] arm64: arm: implement a boot header capability

[Steve Rae]

From: Andre Przywara <andre.przywara at arm.com>

Some SPL loaders (like Allwinner's boot0, and Broadcom's boot0)
require a header before the actual U-Boot binary to both check its
validity and to find other data to load. Sometimes this header may
only be a few bytes of information, and sometimes this might simply
be space that needs to be reserved for a post-processing tool.

Introduce a config option to allow assembler preprocessor commands
to be inserted into the code at the appropriate location; typical
preprocessor commands might be:
  .space 1000
  .word 0x12345678
etc.
Please note that the current code:
  start.S (arm64) and
  vectors.S (arm)
already jumps over some portion of data already, so this option basically
just increases the size of this region (and the resulting binary).

For use with Allwinner's boot0 blob there is a tool called boot0img[1],
which fills the header to allow booting A64 based boards.
For the Pine64 we need a 1536 byte header (including the branch
instruction) at the moment, so we add this to the defconfig.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
Signed-off-by: Steve Rae <srae at broadcom.com>

[1] https://github.com/apritzel/pine64/tree/master/tools

Commit Notes:
- [v3] also updated the subject and the original commit messaage
END

---

Changes in v3:
( v3 submitted by: Steve Rae <srae at broadcom.com>
at the request of: Andre Przywara <andre.przywara at arm.com> )
- changed from just reserving space (with the .space command) to
executing the assembler preprocessor commands

Changes in v2:
( by: Andre Przywara <andre.przywara at arm.com> )

Changes in v1:
( by: Andre Przywara <andre.przywara at arm.com> )

 arch/arm/cpu/armv8/start.S    | 4 ++++
 arch/arm/lib/vectors.S        | 4 ++++
 board/sunxi/Kconfig           | 7 +++++++
 configs/pine64_plus_defconfig | 1 +
 include/configs/bcm28155_ap.h | 4 ++++
 include/configs/sun50i.h      | 5 +++++
 6 files changed, 25 insertions(+)

diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index e933021..9202889 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -21,6 +21,10 @@
 _start:
 	b	reset
 
+#ifdef CONFIG_BOOT0_CODE
+CONFIG_BOOT0_CODE
+#endif
+
 	.align 3
 
 .globl	_TEXT_BASE
diff --git a/arch/arm/lib/vectors.S b/arch/arm/lib/vectors.S
index 49238ed..5dcfab5 100644
--- a/arch/arm/lib/vectors.S
+++ b/arch/arm/lib/vectors.S
@@ -60,6 +60,10 @@ _start:
 	ldr	pc, _irq
 	ldr	pc, _fiq
 
+#ifdef CONFIG_BOOT0_CODE
+CONFIG_BOOT0_CODE
+#endif
+
 /*
  *************************************************************************
  *
diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
index c1ae6f5..d2678c9 100644
--- a/board/sunxi/Kconfig
+++ b/board/sunxi/Kconfig
@@ -15,6 +15,13 @@ config SUNXI_GEN_SUN6I
 	separate ahb reset control registers, custom pmic bus, new style
 	watchdog, etc.
 
+config SUNXI_BOOT0
+	bool "prepare for boot0 header"
+	---help---
+	If U-Boot is loaded from the Allwinner provided boot0 blob, it
+	expects a header area filled with magic values.
+	This option will add some space at the beginning of the image to
+	let a tool later on fill in this header with sensible data.
 
 choice
 	prompt "Sunxi SoC Variant"
diff --git a/configs/pine64_plus_defconfig b/configs/pine64_plus_defconfig
index 489b75c..ef96dab 100644
--- a/configs/pine64_plus_defconfig
+++ b/configs/pine64_plus_defconfig
@@ -9,3 +9,4 @@ CONFIG_DEFAULT_DEVICE_TREE="sun50i-a64-pine64-plus"
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_FPGA is not set
+CONFIG_SUNXI_BOOT0=y
diff --git a/include/configs/bcm28155_ap.h b/include/configs/bcm28155_ap.h
index 889e5db..515552b 100644
--- a/include/configs/bcm28155_ap.h
+++ b/include/configs/bcm28155_ap.h
@@ -137,4 +137,8 @@
 #define CONFIG_USB_GADGET_BCM_UDC_OTG_PHY
 #define CONFIG_USBID_ADDR		0x34052c46
 
+#define CONFIG_BOOT0_CODE	\
+	.word	0xbabeface;	\
+	.word	_end - _start
+
 #endif /* __BCM28155_AP_H */
diff --git a/include/configs/sun50i.h b/include/configs/sun50i.h
index 0fdb4c7..fe9624b 100644
--- a/include/configs/sun50i.h
+++ b/include/configs/sun50i.h
@@ -17,6 +17,11 @@
 #define GICD_BASE		0x1c81000
 #define GICC_BASE		0x1c82000
 
+#ifdef CONFIG_SUNXI_BOOT0
+#define CONFIG_BOOT0_CODE	\
+	.space	1532
+#endif
+
 /*
  * Include common sunxi configuration where most the settings are
  */
-- 
1.8.5