[U-Boot] [PATCH v2 11/23] sunxi: A64: do an RMR switch if started in AArch32 mode

[Simon Glass]

Hi Andre,

On 4 December 2016 at 18:52, Andre Przywara <andre.przywara at arm.com> wrote:
> 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.
>
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
>  arch/arm/include/asm/arch-sunxi/boot0.h | 27 +++++++++++++++++++++++++++
>  board/sunxi/Kconfig                     |  5 +++++
>  2 files changed, 32 insertions(+)

Reviewed-by: Simon Glass <sjg at chromium.org>

>
> diff --git a/arch/arm/include/asm/arch-sunxi/boot0.h b/arch/arm/include/asm/arch-sunxi/boot0.h
> index 6a13db5..7799a03 100644
> --- a/arch/arm/include/asm/arch-sunxi/boot0.h
> +++ b/arch/arm/include/asm/arch-sunxi/boot0.h
> @@ -4,6 +4,33 @@
>   * SPDX-License-Identifier:    GPL-2.0+
>   */
>
> +#if defined(CONFIG_RESERVE_ALLWINNER_BOOT0_HEADER) && !defined(CONFIG_SPL_BUILD)
>  /* reserve space for BOOT0 header information */
>         b       reset
>         .space  1532
> +#elif defined(CONFIG_ARM_BOOT_HOOK_RMR)
> +/* switch into AArch64 if needed */
> +       tst     x0, x0                  // this is "b #0x84" in ARM
> +       b       reset
> +       .space  0x7c
> +       .word   0xe59f1024      // ldr     r1, [pc, #36] ; 0x170000a0
> +       .word   0xe59f0024      // ldr     r0, [pc, #36] ; CONFIG_*_TEXT_BASE
> +       .word   0xe5810000      // str     r0, [r1]
> +       .word   0xf57ff04f      // dsb     sy
> +       .word   0xf57ff06f      // isb     sy
> +       .word   0xee1c0f50      // mrc     15, 0, r0, cr12, cr0, {2} ; RMR
> +       .word   0xe3800003      // orr     r0, r0, #3
> +       .word   0xee0c0f50      // mcr     15, 0, r0, cr12, cr0, {2} ; RMR
> +       .word   0xf57ff06f      // isb     sy
> +       .word   0xe320f003      // wfi
> +       .word   0xeafffffd      // b       @wfi
> +       .word   0x017000a0      // writeable RVBAR mapping address

How come you cannot use the assembler here?

> +#ifdef CONFIG_SPL_BUILD
> +       .word   CONFIG_SPL_TEXT_BASE
> +#else
> +       .word   CONFIG_SYS_TEXT_BASE
> +#endif
> +#else
> +/* normal execution */
> +       b       reset
> +#endif
> diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
> index 0cd57a2..ba72e76 100644
> --- a/board/sunxi/Kconfig
> +++ b/board/sunxi/Kconfig
> @@ -142,6 +142,11 @@ 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
> +       default y if ARM64
> +       select ENABLE_ARM_SOC_BOOT0_HOOK

help?

> +
>  config DRAM_TYPE
>         int "sunxi dram type"
>         depends on MACH_SUN8I_A83T
> --
> 2.8.2
>

Regards,
Simon