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Diffstat (limited to 'arch/riscv/kernel/head.S')
| -rw-r--r-- | arch/riscv/kernel/head.S | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S new file mode 100644 index 000000000000..76af908f87c1 --- /dev/null +++ b/arch/riscv/kernel/head.S @@ -0,0 +1,157 @@ +/* + * Copyright (C) 2012 Regents of the University of California + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <asm/thread_info.h> +#include <asm/asm-offsets.h> +#include <asm/asm.h> +#include <linux/init.h> +#include <linux/linkage.h> +#include <asm/thread_info.h> +#include <asm/page.h> +#include <asm/csr.h> + +__INIT +ENTRY(_start) + /* Mask all interrupts */ + csrw sie, zero + + /* Load the global pointer */ +.option push +.option norelax + la gp, __global_pointer$ +.option pop + + /* + * Disable FPU to detect illegal usage of + * floating point in kernel space + */ + li t0, SR_FS + csrc sstatus, t0 + + /* Pick one hart to run the main boot sequence */ + la a3, hart_lottery + li a2, 1 + amoadd.w a3, a2, (a3) + bnez a3, .Lsecondary_start + + /* Save hart ID and DTB physical address */ + mv s0, a0 + mv s1, a1 + + /* Initialize page tables and relocate to virtual addresses */ + la sp, init_thread_union + THREAD_SIZE + call setup_vm + call relocate + + /* Restore C environment */ + la tp, init_task + sw s0, TASK_TI_CPU(tp) + + la sp, init_thread_union + li a0, ASM_THREAD_SIZE + add sp, sp, a0 + + /* Start the kernel */ + mv a0, s0 + mv a1, s1 + call sbi_save + tail start_kernel + +relocate: + /* Relocate return address */ + li a1, PAGE_OFFSET + la a0, _start + sub a1, a1, a0 + add ra, ra, a1 + + /* Point stvec to virtual address of intruction after sptbr write */ + la a0, 1f + add a0, a0, a1 + csrw stvec, a0 + + /* Compute sptbr for kernel page tables, but don't load it yet */ + la a2, swapper_pg_dir + srl a2, a2, PAGE_SHIFT + li a1, SPTBR_MODE + or a2, a2, a1 + + /* + * Load trampoline page directory, which will cause us to trap to + * stvec if VA != PA, or simply fall through if VA == PA + */ + la a0, trampoline_pg_dir + srl a0, a0, PAGE_SHIFT + or a0, a0, a1 + sfence.vma + csrw sptbr, a0 +1: + /* Set trap vector to spin forever to help debug */ + la a0, .Lsecondary_park + csrw stvec, a0 + + /* Reload the global pointer */ +.option push +.option norelax + la gp, __global_pointer$ +.option pop + + /* Switch to kernel page tables */ + csrw sptbr, a2 + + ret + +.Lsecondary_start: +#ifdef CONFIG_SMP + li a1, CONFIG_NR_CPUS + bgeu a0, a1, .Lsecondary_park + + /* Set trap vector to spin forever to help debug */ + la a3, .Lsecondary_park + csrw stvec, a3 + + slli a3, a0, LGREG + la a1, __cpu_up_stack_pointer + la a2, __cpu_up_task_pointer + add a1, a3, a1 + add a2, a3, a2 + + /* + * This hart didn't win the lottery, so we wait for the winning hart to + * get far enough along the boot process that it should continue. + */ +.Lwait_for_cpu_up: + /* FIXME: We should WFI to save some energy here. */ + REG_L sp, (a1) + REG_L tp, (a2) + beqz sp, .Lwait_for_cpu_up + beqz tp, .Lwait_for_cpu_up + fence + + /* Enable virtual memory and relocate to virtual address */ + call relocate + + tail smp_callin +#endif + +.Lsecondary_park: + /* We lack SMP support or have too many harts, so park this hart */ + wfi + j .Lsecondary_park +END(_start) + +__PAGE_ALIGNED_BSS + /* Empty zero page */ + .balign PAGE_SIZE +ENTRY(empty_zero_page) + .fill (empty_zero_page + PAGE_SIZE) - ., 1, 0x00 +END(empty_zero_page) |