diff options
author | Andre Przywara <andre.przywara@arm.com> | 2017-01-02 11:48:36 +0000 |
---|---|---|
committer | Jagan Teki <jagan@openedev.com> | 2017-01-04 16:37:42 +0100 |
commit | 83843c9b3ac511e97b844db70553a2a8966dd44a (patch) | |
tree | 378df5a99de591aa8a09664a17f4c6b5e6e9e5fb /arch/arm/mach-sunxi | |
parent | b5402d13d4a3fe49af884ba7d5d32700af911536 (diff) | |
download | u-boot-83843c9b3ac511e97b844db70553a2a8966dd44a.zip u-boot-83843c9b3ac511e97b844db70553a2a8966dd44a.tar.gz u-boot-83843c9b3ac511e97b844db70553a2a8966dd44a.tar.bz2 |
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 <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Diffstat (limited to 'arch/arm/mach-sunxi')
-rw-r--r-- | arch/arm/mach-sunxi/rmr_switch.S | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/arch/arm/mach-sunxi/rmr_switch.S b/arch/arm/mach-sunxi/rmr_switch.S new file mode 100644 index 0000000..cefa930 --- /dev/null +++ b/arch/arm/mach-sunxi/rmr_switch.S @@ -0,0 +1,41 @@ +@ +@ ARMv8 RMR reset sequence on Allwinner SoCs. +@ +@ All 64-bit capable Allwinner SoCs reset in AArch32 (and continue to +@ exectute the Boot ROM in this state), so we need to switch to AArch64 +@ at some point. +@ Section G6.2.133 of the ARMv8 ARM describes the Reset Management Register +@ (RMR), which triggers a warm-reset of a core and can request to switch +@ into a different execution state (AArch32 or AArch64). +@ The address at which execution starts after the reset is held in the +@ RVBAR system register, which is architecturally read-only. +@ Allwinner provides a writable alias of this register in MMIO space, so +@ we can easily set the start address of AArch64 code. +@ This code below switches to AArch64 and starts execution at the specified +@ start address. It needs to be assembled by an ARM(32) assembler and +@ the machine code must be inserted as verbatim .word statements into the +@ beginning of the AArch64 U-Boot code. +@ To get the encoded bytes, use: +@ ${CROSS_COMPILE}gcc -c -o rmr_switch.o rmr_switch.S +@ ${CROSS_COMPILE}objdump -d rmr_switch.o +@ +@ The resulting words should be inserted into the U-Boot file at +@ arch/arm/include/asm/arch-sunxi/boot0.h. +@ +@ This file is not build by the U-Boot build system, but provided only as a +@ reference and to be able to regenerate a (probably fixed) version of this +@ code found in encoded form in boot0.h. + +.text + + ldr r1, =0x017000a0 @ MMIO mapped RVBAR[0] register + ldr r0, =0x57aA7add @ start address, to be replaced + str r0, [r1] + dsb sy + isb sy + mrc 15, 0, r0, cr12, cr0, 2 @ read RMR register + orr r0, r0, #3 @ request reset in AArch64 + mcr 15, 0, r0, cr12, cr0, 2 @ write RMR register + isb sy +1: wfi + b 1b |