1/* 2 * Copyright (C) 2012 Regents of the University of California 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation, version 2. 7 * 8 * This program is distributed in the hope that it will be useful, 9 * but WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 * GNU General Public License for more details. 12 */ 13 14#include <asm/thread_info.h> 15#include <asm/asm-offsets.h> 16#include <asm/asm.h> 17#include <linux/init.h> 18#include <linux/linkage.h> 19#include <asm/thread_info.h> 20#include <asm/page.h> 21#include <asm/csr.h> 22 23__INIT 24ENTRY(_start) 25 /* Mask all interrupts */ 26 csrw sie, zero 27 28 /* Load the global pointer */ 29.option push 30.option norelax 31 la gp, __global_pointer$ 32.option pop 33 34 /* 35 * Disable FPU to detect illegal usage of 36 * floating point in kernel space 37 */ 38 li t0, SR_FS 39 csrc sstatus, t0 40 41 /* Pick one hart to run the main boot sequence */ 42 la a3, hart_lottery 43 li a2, 1 44 amoadd.w a3, a2, (a3) 45 bnez a3, .Lsecondary_start 46 47 /* Save hart ID and DTB physical address */ 48 mv s0, a0 49 mv s1, a1 50 la a2, boot_cpu_hartid 51 REG_S a0, (a2) 52 53 /* Initialize page tables and relocate to virtual addresses */ 54 la sp, init_thread_union + THREAD_SIZE 55 call setup_vm 56 call relocate 57 58 /* Restore C environment */ 59 la tp, init_task 60 sw zero, TASK_TI_CPU(tp) 61 62 la sp, init_thread_union 63 li a0, ASM_THREAD_SIZE 64 add sp, sp, a0 65 66 /* Start the kernel */ 67 mv a0, s0 68 mv a1, s1 69 call parse_dtb 70 tail start_kernel 71 72relocate: 73 /* Relocate return address */ 74 li a1, PAGE_OFFSET 75 la a0, _start 76 sub a1, a1, a0 77 add ra, ra, a1 78 79 /* Point stvec to virtual address of intruction after satp write */ 80 la a0, 1f 81 add a0, a0, a1 82 csrw stvec, a0 83 84 /* Compute satp for kernel page tables, but don't load it yet */ 85 la a2, swapper_pg_dir 86 srl a2, a2, PAGE_SHIFT 87 li a1, SATP_MODE 88 or a2, a2, a1 89 90 /* 91 * Load trampoline page directory, which will cause us to trap to 92 * stvec if VA != PA, or simply fall through if VA == PA 93 */ 94 la a0, trampoline_pg_dir 95 srl a0, a0, PAGE_SHIFT 96 or a0, a0, a1 97 sfence.vma 98 csrw sptbr, a0 99.align 2 1001: 101 /* Set trap vector to spin forever to help debug */ 102 la a0, .Lsecondary_park 103 csrw stvec, a0 104 105 /* Reload the global pointer */ 106.option push 107.option norelax 108 la gp, __global_pointer$ 109.option pop 110 111 /* Switch to kernel page tables */ 112 csrw sptbr, a2 113 114 ret 115 116.Lsecondary_start: 117#ifdef CONFIG_SMP 118 li a1, CONFIG_NR_CPUS 119 bgeu a0, a1, .Lsecondary_park 120 121 /* Set trap vector to spin forever to help debug */ 122 la a3, .Lsecondary_park 123 csrw stvec, a3 124 125 slli a3, a0, LGREG 126 la a1, __cpu_up_stack_pointer 127 la a2, __cpu_up_task_pointer 128 add a1, a3, a1 129 add a2, a3, a2 130 131 /* 132 * This hart didn't win the lottery, so we wait for the winning hart to 133 * get far enough along the boot process that it should continue. 134 */ 135.Lwait_for_cpu_up: 136 /* FIXME: We should WFI to save some energy here. */ 137 REG_L sp, (a1) 138 REG_L tp, (a2) 139 beqz sp, .Lwait_for_cpu_up 140 beqz tp, .Lwait_for_cpu_up 141 fence 142 143 /* Enable virtual memory and relocate to virtual address */ 144 call relocate 145 146 tail smp_callin 147#endif 148 149.align 2 150.Lsecondary_park: 151 /* We lack SMP support or have too many harts, so park this hart */ 152 wfi 153 j .Lsecondary_park 154END(_start) 155 156__PAGE_ALIGNED_BSS 157 /* Empty zero page */ 158 .balign PAGE_SIZE 159