mirror of
https://github.com/smaeul/u-boot.git
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924de3216e
This adds comments regarding the ordering and purpose of certain instructions as I understand them. Signed-off-by: Sean Anderson <seanga2@gmail.com> Reviewed-by: Bin Meng <bin.meng@windriver.com> Reviewed-by: Rick Chen <rick@andestech.com> Reviewed-by: Leo Liang <ycliang@andestech.com>
447 lines
9.4 KiB
ArmAsm
447 lines
9.4 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Startup Code for RISC-V Core
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*
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* Copyright (c) 2017 Microsemi Corporation.
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* Copyright (c) 2017 Padmarao Begari <Padmarao.Begari@microsemi.com>
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*
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* Copyright (C) 2017 Andes Technology Corporation
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* Rick Chen, Andes Technology Corporation <rick@andestech.com>
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*/
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#include <asm-offsets.h>
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#include <config.h>
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#include <common.h>
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#include <elf.h>
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#include <asm/encoding.h>
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#include <generated/asm-offsets.h>
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#ifdef CONFIG_32BIT
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#define LREG lw
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#define SREG sw
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#define REGBYTES 4
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#define RELOC_TYPE R_RISCV_32
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#define SYM_INDEX 0x8
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#define SYM_SIZE 0x10
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#else
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#define LREG ld
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#define SREG sd
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#define REGBYTES 8
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#define RELOC_TYPE R_RISCV_64
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#define SYM_INDEX 0x20
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#define SYM_SIZE 0x18
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#endif
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.section .data
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secondary_harts_relocation_error:
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.ascii "Relocation of secondary harts has failed, error %d\n"
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.section .text
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.globl _start
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_start:
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#if CONFIG_IS_ENABLED(RISCV_MMODE)
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csrr a0, CSR_MHARTID
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#endif
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/*
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* Save hart id and dtb pointer. The thread pointer register is not
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* modified by C code. It is used by secondary_hart_loop.
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*/
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mv tp, a0
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mv s1, a1
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/*
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* Set the global data pointer to a known value in case we get a very
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* early trap. The global data pointer will be set its actual value only
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* after it has been initialized.
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*/
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mv gp, zero
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/*
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* Set the trap handler. This must happen after initializing gp because
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* the handler may use it.
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*/
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la t0, trap_entry
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csrw MODE_PREFIX(tvec), t0
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/*
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* Mask all interrupts. Interrupts are disabled globally (in m/sstatus)
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* for U-Boot, but we will need to read m/sip to determine if we get an
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* IPI
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*/
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csrw MODE_PREFIX(ie), zero
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#if CONFIG_IS_ENABLED(SMP)
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/* check if hart is within range */
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/* tp: hart id */
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li t0, CONFIG_NR_CPUS
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bge tp, t0, hart_out_of_bounds_loop
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/* set xSIE bit to receive IPIs */
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#if CONFIG_IS_ENABLED(RISCV_MMODE)
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li t0, MIE_MSIE
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#else
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li t0, SIE_SSIE
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#endif
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csrs MODE_PREFIX(ie), t0
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#endif
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/*
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* Set stackpointer in internal/ex RAM to call board_init_f
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*/
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call_board_init_f:
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li t0, -16
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#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
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li t1, CONFIG_SPL_STACK
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#else
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li t1, CONFIG_SYS_INIT_SP_ADDR
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#endif
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and sp, t1, t0 /* force 16 byte alignment */
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call_board_init_f_0:
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mv a0, sp
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jal board_init_f_alloc_reserve
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/*
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* Save global data pointer for later. We don't set it here because it
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* is not initialized yet.
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*/
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mv s0, a0
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/* setup stack */
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#if CONFIG_IS_ENABLED(SMP)
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/* tp: hart id */
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slli t0, tp, CONFIG_STACK_SIZE_SHIFT
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sub sp, a0, t0
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#else
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mv sp, a0
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#endif
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#ifndef CONFIG_XIP
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/*
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* Pick hart to initialize global data and run U-Boot. The other harts
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* wait for initialization to complete.
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*/
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la t0, hart_lottery
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li s2, 1
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amoswap.w s2, t1, 0(t0)
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bnez s2, wait_for_gd_init
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#else
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/*
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* FIXME: gp is set before it is initialized. If an XIP U-Boot ever
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* encounters a pending IPI on boot it is liable to jump to whatever
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* memory happens to be in ipi_data.addr on boot. It may also run into
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* problems if it encounters an exception too early (because printf/puts
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* accesses gd).
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*/
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mv gp, s0
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bnez tp, secondary_hart_loop
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#endif
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#ifdef CONFIG_OF_PRIOR_STAGE
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la t0, prior_stage_fdt_address
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SREG s1, 0(t0)
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#endif
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jal board_init_f_init_reserve
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SREG s1, GD_FIRMWARE_FDT_ADDR(gp)
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/* save the boot hart id to global_data */
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SREG tp, GD_BOOT_HART(gp)
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#ifndef CONFIG_XIP
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la t0, available_harts_lock
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amoswap.w.rl zero, zero, 0(t0)
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wait_for_gd_init:
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la t0, available_harts_lock
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li t1, 1
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1: amoswap.w.aq t1, t1, 0(t0)
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bnez t1, 1b
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/*
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* Set the global data pointer only when gd_t has been initialized.
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* This was already set by arch_setup_gd on the boot hart, but all other
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* harts' global data pointers gets set here.
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*/
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mv gp, s0
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/* register available harts in the available_harts mask */
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li t1, 1
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sll t1, t1, tp
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LREG t2, GD_AVAILABLE_HARTS(gp)
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or t2, t2, t1
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SREG t2, GD_AVAILABLE_HARTS(gp)
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amoswap.w.rl zero, zero, 0(t0)
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/*
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* Continue on hart lottery winner, others branch to
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* secondary_hart_loop.
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*/
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bnez s2, secondary_hart_loop
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#endif
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/* Enable cache */
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jal icache_enable
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jal dcache_enable
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#ifdef CONFIG_DEBUG_UART
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jal debug_uart_init
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#endif
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mv a0, zero /* a0 <-- boot_flags = 0 */
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la t5, board_init_f
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jalr t5 /* jump to board_init_f() */
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#ifdef CONFIG_SPL_BUILD
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spl_clear_bss:
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la t0, __bss_start
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la t1, __bss_end
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beq t0, t1, spl_stack_gd_setup
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spl_clear_bss_loop:
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SREG zero, 0(t0)
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addi t0, t0, REGBYTES
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blt t0, t1, spl_clear_bss_loop
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spl_stack_gd_setup:
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jal spl_relocate_stack_gd
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/* skip setup if we did not relocate */
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beqz a0, spl_call_board_init_r
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mv s0, a0
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/* setup stack on main hart */
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#if CONFIG_IS_ENABLED(SMP)
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/* tp: hart id */
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slli t0, tp, CONFIG_STACK_SIZE_SHIFT
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sub sp, s0, t0
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#else
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mv sp, s0
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#endif
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#if CONFIG_IS_ENABLED(SMP)
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/* set new stack and global data pointer on secondary harts */
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spl_secondary_hart_stack_gd_setup:
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la a0, secondary_hart_relocate
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mv a1, s0
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mv a2, s0
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mv a3, zero
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jal smp_call_function
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/* hang if relocation of secondary harts has failed */
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beqz a0, 1f
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mv a1, a0
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la a0, secondary_harts_relocation_error
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jal printf
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jal hang
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#endif
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/* set new global data pointer on main hart */
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1: mv gp, s0
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spl_call_board_init_r:
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mv a0, zero
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mv a1, zero
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jal board_init_r
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#endif
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/*
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* void relocate_code(addr_sp, gd, addr_moni)
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*
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* This "function" does not return, instead it continues in RAM
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* after relocating the monitor code.
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*
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*/
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.globl relocate_code
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relocate_code:
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mv s2, a0 /* save addr_sp */
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mv s3, a1 /* save addr of gd */
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mv s4, a2 /* save addr of destination */
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/*
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*Set up the stack
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*/
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stack_setup:
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#if CONFIG_IS_ENABLED(SMP)
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/* tp: hart id */
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slli t0, tp, CONFIG_STACK_SIZE_SHIFT
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sub sp, s2, t0
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#else
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mv sp, s2
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#endif
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la t0, _start
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sub t6, s4, t0 /* t6 <- relocation offset */
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beq t0, s4, clear_bss /* skip relocation */
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mv t1, s4 /* t1 <- scratch for copy_loop */
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la t3, __bss_start
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sub t3, t3, t0 /* t3 <- __bss_start_ofs */
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add t2, t0, t3 /* t2 <- source end address */
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copy_loop:
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LREG t5, 0(t0)
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addi t0, t0, REGBYTES
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SREG t5, 0(t1)
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addi t1, t1, REGBYTES
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blt t0, t2, copy_loop
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/*
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* Update dynamic relocations after board_init_f
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*/
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fix_rela_dyn:
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la t1, __rel_dyn_start
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la t2, __rel_dyn_end
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beq t1, t2, clear_bss
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add t1, t1, t6 /* t1 <- rela_dyn_start in RAM */
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add t2, t2, t6 /* t2 <- rela_dyn_end in RAM */
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/*
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* skip first reserved entry: address, type, addend
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*/
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j 10f
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6:
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LREG t5, -(REGBYTES*2)(t1) /* t5 <-- relocation info:type */
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li t3, R_RISCV_RELATIVE /* reloc type R_RISCV_RELATIVE */
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bne t5, t3, 8f /* skip non-RISCV_RELOC entries */
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LREG t3, -(REGBYTES*3)(t1)
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LREG t5, -(REGBYTES)(t1) /* t5 <-- addend */
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add t5, t5, t6 /* t5 <-- location to fix up in RAM */
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add t3, t3, t6 /* t3 <-- location to fix up in RAM */
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SREG t5, 0(t3)
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j 10f
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8:
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la t4, __dyn_sym_start
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add t4, t4, t6
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9:
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LREG t5, -(REGBYTES*2)(t1) /* t5 <-- relocation info:type */
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srli t0, t5, SYM_INDEX /* t0 <--- sym table index */
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andi t5, t5, 0xFF /* t5 <--- relocation type */
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li t3, RELOC_TYPE
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bne t5, t3, 10f /* skip non-addned entries */
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LREG t3, -(REGBYTES*3)(t1)
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li t5, SYM_SIZE
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mul t0, t0, t5
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add s5, t4, t0
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LREG t0, -(REGBYTES)(t1) /* t0 <-- addend */
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LREG t5, REGBYTES(s5)
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add t5, t5, t0
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add t5, t5, t6 /* t5 <-- location to fix up in RAM */
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add t3, t3, t6 /* t3 <-- location to fix up in RAM */
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SREG t5, 0(t3)
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10:
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addi t1, t1, (REGBYTES*3)
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ble t1, t2, 6b
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/*
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* trap update
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*/
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la t0, trap_entry
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add t0, t0, t6
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csrw MODE_PREFIX(tvec), t0
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clear_bss:
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la t0, __bss_start /* t0 <- rel __bss_start in FLASH */
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add t0, t0, t6 /* t0 <- rel __bss_start in RAM */
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la t1, __bss_end /* t1 <- rel __bss_end in FLASH */
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add t1, t1, t6 /* t1 <- rel __bss_end in RAM */
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beq t0, t1, relocate_secondary_harts
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clbss_l:
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SREG zero, 0(t0) /* clear loop... */
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addi t0, t0, REGBYTES
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blt t0, t1, clbss_l
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relocate_secondary_harts:
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#if CONFIG_IS_ENABLED(SMP)
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/* send relocation IPI */
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la t0, secondary_hart_relocate
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add a0, t0, t6
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/* store relocation offset */
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mv s5, t6
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mv a1, s2
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mv a2, s3
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mv a3, zero
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jal smp_call_function
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/* hang if relocation of secondary harts has failed */
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beqz a0, 1f
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mv a1, a0
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la a0, secondary_harts_relocation_error
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jal printf
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jal hang
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/* restore relocation offset */
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1: mv t6, s5
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#endif
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/*
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* We are done. Do not return, instead branch to second part of board
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* initialization, now running from RAM.
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*/
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call_board_init_r:
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jal invalidate_icache_all
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jal flush_dcache_all
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la t0, board_init_r /* offset of board_init_r() */
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add t4, t0, t6 /* real address of board_init_r() */
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/*
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* setup parameters for board_init_r
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*/
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mv a0, s3 /* gd_t */
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mv a1, s4 /* dest_addr */
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/*
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* jump to it ...
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*/
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jr t4 /* jump to board_init_r() */
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#if CONFIG_IS_ENABLED(SMP)
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hart_out_of_bounds_loop:
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/* Harts in this loop are out of bounds, increase CONFIG_NR_CPUS. */
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wfi
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j hart_out_of_bounds_loop
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/* SMP relocation entry */
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secondary_hart_relocate:
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/* a1: new sp */
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/* a2: new gd */
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/* tp: hart id */
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/* setup stack */
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slli t0, tp, CONFIG_STACK_SIZE_SHIFT
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sub sp, a1, t0
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/* update global data pointer */
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mv gp, a2
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#endif
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/*
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* Interrupts are disabled globally, but they can still be read from m/sip. The
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* wfi function will wake us up if we get an IPI, even if we do not trap.
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*/
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secondary_hart_loop:
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wfi
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#if CONFIG_IS_ENABLED(SMP)
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csrr t0, MODE_PREFIX(ip)
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#if CONFIG_IS_ENABLED(RISCV_MMODE)
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andi t0, t0, MIE_MSIE
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#else
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andi t0, t0, SIE_SSIE
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#endif
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beqz t0, secondary_hart_loop
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mv a0, tp
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jal handle_ipi
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#endif
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j secondary_hart_loop
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