arch/riscv/kernel/smpboot.c

   1 /*
   2  * SMP initialisation and IPI support
   3  * Based on arch/arm64/kernel/smp.c
   4  *
   5  * Copyright (C) 2012 ARM Ltd.
   6  * Copyright (C) 2015 Regents of the University of California
   7  * Copyright (C) 2017 SiFive
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 #include <linux/sched.h>
  24 #include <linux/kernel_stat.h>
  25 #include <linux/notifier.h>
  26 #include <linux/cpu.h>
  27 #include <linux/percpu.h>
  28 #include <linux/delay.h>
  29 #include <linux/err.h>
  30 #include <linux/irq.h>
  31 #include <linux/of.h>
  32 #include <linux/sched/task_stack.h>
  33 #include <linux/sched/mm.h>
  34 #include <asm/irq.h>
  35 #include <asm/mmu_context.h>
  36 #include <asm/tlbflush.h>
  37 #include <asm/sections.h>
  38 #include <asm/sbi.h>
  39
  40 void *__cpu_up_stack_pointer[NR_CPUS];
  41 void *__cpu_up_task_pointer[NR_CPUS];
  42
  43 void __init smp_prepare_boot_cpu(void)
  44 {
  45 }
  46
  47 void __init smp_prepare_cpus(unsigned int max_cpus)
  48 {
  49 }
  50
  51 void __init setup_smp(void)
  52 {
  53         struct device_node *dn = NULL;
  54         int hart;
  55         bool found_boot_cpu = false;
  56         int cpuid = 1;
  57
  58         while ((dn = of_find_node_by_type(dn, "cpu"))) {
  59                 hart = riscv_of_processor_hartid(dn);
  60                 if (hart < 0)
  61                         continue;
  62
  63                 if (hart == cpuid_to_hartid_map(0)) {
  64                         BUG_ON(found_boot_cpu);
  65                         found_boot_cpu = 1;
  66                         continue;
  67                 }
  68
  69                 cpuid_to_hartid_map(cpuid) = hart;
  70                 set_cpu_possible(cpuid, true);
  71                 set_cpu_present(cpuid, true);
  72                 cpuid++;
  73         }
  74
  75         BUG_ON(!found_boot_cpu);
  76 }
  77
  78 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
  79 {
  80         int hartid = cpuid_to_hartid_map(cpu);
  81         tidle->thread_info.cpu = cpu;
  82
  83         /*
  84          * On RISC-V systems, all harts boot on their own accord.  Our _start
  85          * selects the first hart to boot the kernel and causes the remainder
  86          * of the harts to spin in a loop waiting for their stack pointer to be
  87          * setup by that main hart.  Writing __cpu_up_stack_pointer signals to
  88          * the spinning harts that they can continue the boot process.
  89          */
  90         smp_mb();
  91         WRITE_ONCE(__cpu_up_stack_pointer[hartid],
  92                   task_stack_page(tidle) + THREAD_SIZE);
  93         WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
  94
  95         while (!cpu_online(cpu))
  96                 cpu_relax();
  97
  98         return 0;
  99 }
 100
 101 void __init smp_cpus_done(unsigned int max_cpus)
 102 {
 103 }
 104
 105 /*
 106  * C entry point for a secondary processor.
 107  */
 108 asmlinkage void __init smp_callin(void)
 109 {
 110         struct mm_struct *mm = &init_mm;
 111
 112         /* All kernel threads share the same mm context.  */
 113         mmgrab(mm);
 114         current->active_mm = mm;
 115
 116         trap_init();
 117         notify_cpu_starting(smp_processor_id());
 118         set_cpu_online(smp_processor_id(), 1);
 119         /*
 120          * Remote TLB flushes are ignored while the CPU is offline, so emit
 121          * a local TLB flush right now just in case.
 122          */
 123         local_flush_tlb_all();
 124         /*
 125          * Disable preemption before enabling interrupts, so we don't try to
 126          * schedule a CPU that hasn't actually started yet.
 127          */
 128         preempt_disable();
 129         local_irq_enable();
 130         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 131 }