sunxi: A64: do an RMR switch if started in AArch32 mode

[u-boot] / board / sunxi / Kconfig

diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
index 0cd57a2d85fa3170338dd2b4285362ea0cd2c604..f02057386558aa90e2facb551cc0929d5a6795ac 100644 (file)
--- a/board/sunxi/Kconfig
+++ b/board/sunxi/Kconfig
@@ -142,6 +142,20 @@ config RESERVE_ALLWINNER_BOOT0_HEADER
        blob relies on this information to load and execute U-Boot.
        Only needed on 64-bit Allwinner boards so far when using boot0.
 
+config ARM_BOOT_HOOK_RMR
+       bool
+       depends on ARM64
+       default y
+       select ENABLE_ARM_SOC_BOOT0_HOOK
+       ---help---
+       Insert some ARM32 code at the very beginning of the U-Boot binary
+       which uses an RMR register write to bring the core into AArch64 mode.
+       The very first instruction acts as a switch, since it's carefully
+       chosen to be a NOP in one mode and a branch in the other, so the
+       code would only be executed if not already in AArch64.
+       This allows both the SPL and the U-Boot proper to be entered in
+       either mode and switch to AArch64 if needed.
+
 config DRAM_TYPE
        int "sunxi dram type"
        depends on MACH_SUN8I_A83T