From 83843c9b3ac511e97b844db70553a2a8966dd44a Mon Sep 17 00:00:00 2001 From: Andre Przywara Date: Mon, 2 Jan 2017 11:48:36 +0000 Subject: sunxi: A64: do an RMR switch if started in AArch32 mode The Allwinner A64 SoC starts execution in AArch32 mode, and both the boot ROM and Allwinner's boot0 keep running in this mode. So U-Boot gets entered in 32-bit, although we want it to run in AArch64. By using a "magic" instruction, which happens to be an almost-NOP in AArch64 and a branch in AArch32, we differentiate between being entered in 64-bit or 32-bit mode. If in 64-bit mode, we proceed with the branch to reset, but in 32-bit mode we trigger an RMR write to bring the core into AArch64/EL3 and re-enter U-Boot at CONFIG_SYS_TEXT_BASE. This allows a 64-bit U-Boot to be both entered in 32 and 64-bit mode, so we can use the same start code for the SPL and the U-Boot proper. We use the existing custom header (boot0.h) functionality, but restrict the existing boot0 header reservation to the non-SPL build now. A SPL wouldn't need such header anyway. This allows to have both options defined and lets us use one for the SPL and the other for U-Boot proper. Also add arch/arm/mach-sunxi/rmr_switch.S, which contains the original ARM assembly code and instructions how to re-generate the encoded version. Signed-off-by: Andre Przywara Acked-by: Maxime Ripard Reviewed-by: Jagan Teki --- board/sunxi/Kconfig | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'board') diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig index 0cd57a2d85f..f0205738655 100644 --- 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 -- cgit v1.2.3