在 2020-11-19星期四的 10:54 +0000，Andre Przywara写道：
> So far we did not support the BootROM based FEL USB debug mode on the
> 64-bit builds for Allwinner SoCs: The BootROM is using AArch32, but
> the
> SPL runs in AArch64.
> Returning back to AArch32 was not working as expected, since the RMR
> reset into 32-bit mode always starts execution in the BootROM, but
> not
> in the FEL routine.
>
> After some debug and research and with help via IRC, the CPU hotplug
> mechanism emerged as a solution: If a certain R_CPUCFG register
> contains
> some magic, the BootROM will immediately branch to an address stored
> in
> some other register. This works well for our purposes.
>
> Enable the FEL feature by providing early AArch32 code to first save
> the
> FEL state, *before* initially entering AArch64.
> If we eventually determine that we should return to FEL, we reset
> back
> into AArch32, and use the CPU hotplug mechanism to run some small
> AArch32 code snippet that restores the initially saved FEL state.
>
> That allows the normal AArch64 SPL build to be loaded via the sunxi-
> fel
> tool, with it returning into FEL mode, so that other payloads can be
> transferred via FEL as well.
>
> Tested on A64, H5 and H6.
>
> Signed-off-by: Andre Przywara <andre.przyw...@arm.com>
Tested-by: Icenowy Zheng <icen...@aosc.io>
> ---
> arch/arm/cpu/armv8/Makefile | 2 +
> arch/arm/cpu/armv8/fel_utils.S | 78
> +++++++++++++++++++++++++
> arch/arm/include/asm/arch-sunxi/boot0.h | 14 +++++
> include/configs/sunxi-common.h | 2 -
> 4 files changed, 94 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm/cpu/armv8/fel_utils.S
>
> diff --git a/arch/arm/cpu/armv8/Makefile
> b/arch/arm/cpu/armv8/Makefile
> index 93d26f98568..f7b4a5ee46c 100644
> --- a/arch/arm/cpu/armv8/Makefile
> +++ b/arch/arm/cpu/armv8/Makefile
> @@ -27,6 +27,8 @@ obj-$(CONFIG_ARM_SMCCC) += smccc-call.o
>
> ifndef CONFIG_SPL_BUILD
> obj-$(CONFIG_ARMV8_SPIN_TABLE) += spin_table.o spin_table_v8.o
> +else
> +obj-$(CONFIG_ARCH_SUNXI) += fel_utils.o
> endif
> obj-$(CONFIG_$(SPL_)ARMV8_SEC_FIRMWARE_SUPPORT) += sec_firmware.o
> sec_firmware_asm.o
>
> diff --git a/arch/arm/cpu/armv8/fel_utils.S
> b/arch/arm/cpu/armv8/fel_utils.S
> new file mode 100644
> index 00000000000..334fdef7fa0
> --- /dev/null
> +++ b/arch/arm/cpu/armv8/fel_utils.S
> @@ -0,0 +1,78 @@
> +/*
> + * Utility functions for FEL mode, when running SPL in AArch64.
> + *
> + * Copyright (c) 2017 Arm Ltd.
> + *
> + * SPDX-License-Identifier: GPL-2.0+
> + */
> +
> +#include <asm-offsets.h>
> +#include <config.h>
> +#include <asm/system.h>
> +#include <linux/linkage.h>
> +
> +/*
> + * We don't overwrite save_boot_params() here, to save the FEL state
> upon
> + * entry, since this would run *after* the RMR reset, which clobbers
> that
> + * state.
> + * Instead we store the state _very_ early in the boot0 hook,
> *before*
> + * resetting to AArch64.
> + */
> +
> +/*
> + * The FEL routines in BROM run in AArch32.
> + * Reset back into 32-bit mode here and restore the saved FEL state
> + * afterwards.
> + * Resetting back into AArch32/EL3 using the RMR always enters the
> BROM,
> + * but we can use the CPU hotplug mechanism to branch back to our
> code
> + * immediately.
> + */
> +ENTRY(return_to_fel)
> + /*
> + * the RMR reset will clear all registers, so save the
> arguments
> + * (LR and SP) in the fel_stash structure, which we read
> anyways later
> + */
> + adr x2, fel_stash
> + str w0, [x2]
> + str w1, [x2, #4]
> +
> + adr x1, fel_stash_addr // to find the fel_stash
> address in AA32
> + str w2, [x1]
> +
> + ldr x0, =0xfa50392f // CPU hotplug magic
> +#ifndef CONFIG_MACH_SUN50I_H6
> + ldr x2, =(SUNXI_CPUCFG_BASE + 0x1a4) // offset for CPU
> hotplug base
> + str w0, [x2, #0x8]
> +#else
> + ldr x2, =(SUNXI_RTC_BASE + 0x1b8) //
> BOOT_CPU_HP_FLAG_REG
> + str w0, [x2], #0x4
> +#endif
> + adr x0, back_in_32
> + str w0, [x2]
> +
> + dsb sy
> + isb sy
> + mov x0, #2 // RMR reset into AArch32
> + dsb sy
> + msr RMR_EL3, x0
> + isb sy
> +1: wfi
> + b 1b
> +
> +/* AArch32 code to restore the state from fel_stash and return back
> to FEL. */
> +back_in_32:
> + .word 0xe59f0028 // ldr r0, [pc, #40] ; load
> fel_stash address
> + .word 0xe5901008 // ldr r1, [r0, #8]
> + .word 0xe129f001 // msr CPSR_fc, r1
> + .word 0xf57ff06f // isb
> + .word 0xe590d000 // ldr sp, [r0]
> + .word 0xe590e004 // ldr lr, [r0, #4]
> + .word 0xe5901010 // ldr r1, [r0, #16]
> + .word 0xee0c1f10 // mcr 15, 0, r1, cr12, cr0, {0} ;
> VBAR
> + .word 0xe590100c // ldr r1, [r0, #12]
> + .word 0xee011f10 // mcr 15, 0, r1, cr1, cr0, {0} ;
> SCTLR
> + .word 0xf57ff06f // isb
> + .word 0xe12fff1e // bx lr ; return to
> FEL
> +fel_stash_addr:
> + .word 0x00000000 // receives fel_stash addr, by AA64
> code above
> +ENDPROC(return_to_fel)
> diff --git a/arch/arm/include/asm/arch-sunxi/boot0.h
> b/arch/arm/include/asm/arch-sunxi/boot0.h
> index 54c144afd8c..46d0f0666c2 100644
> --- a/arch/arm/include/asm/arch-sunxi/boot0.h
> +++ b/arch/arm/include/asm/arch-sunxi/boot0.h
> @@ -15,6 +15,19 @@
> tst x0, x0 // this is "b #0x84" in ARM
> b reset
> .space 0x7c
> +
> + .word 0xe28f0058 // add r0, pc, #88
> + .word 0xe59f1054 // ldr r1, [pc, #84]
> + .word 0xe0800001 // add r0, r0, r1
> + .word 0xe580d000 // str sp, [r0]
> + .word 0xe580e004 // str lr, [r0, #4]
> + .word 0xe10fe000 // mrs lr, CPSR
> + .word 0xe580e008 // str lr, [r0, #8]
> + .word 0xee11ef10 // mrc 15, 0, lr, cr1, cr0, {0}
> + .word 0xe580e00c // str lr, [r0, #12]
> + .word 0xee1cef10 // mrc 15, 0, lr, cr12, cr0, {0}
> + .word 0xe580e010 // str lr, [r0, #16]
> +
> .word 0xe59f1024 // ldr r1, [pc, #36] ; 0x170000a0
> .word 0xe59f0024 // ldr r0, [pc, #36] ;
> CONFIG_*_TEXT_BASE
> .word 0xe5810000 // str r0, [r1]
> @@ -36,6 +49,7 @@
> #else
> .word CONFIG_SYS_TEXT_BASE
> #endif
> + .word fel_stash - .
> #else
> /* normal execution */
> b reset
> diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-
> common.h
> index a6a4879523a..203cb10fbab 100644
> --- a/include/configs/sunxi-common.h
> +++ b/include/configs/sunxi-common.h
> @@ -163,9 +163,7 @@
>
> #define CONFIG_SYS_MONITOR_LEN (768 << 10) /*
> 768 KiB */
>
> -#ifndef CONFIG_ARM64 /* AArch64 FEL support is not ready yet
> */
> #define CONFIG_SPL_BOARD_LOAD_IMAGE
> -#endif
>
> /*
> * We cannot use expressions here, because expressions won't be
> evaluated in
> --
> 2.17.5
>
