arch/riscv/kernel/cpu-hotplug.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2020 Western Digital Corporation or its affiliates.
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/mm.h>
   8 #include <linux/sched.h>
   9 #include <linux/err.h>
  10 #include <linux/irq.h>
  11 #include <linux/cpu.h>
  12 #include <linux/sched/hotplug.h>
  13 #include <asm/irq.h>
  14 #include <asm/cpu_ops.h>
  15 #include <asm/sbi.h>
  16
  17 void cpu_stop(void);
  18 void arch_cpu_idle_dead(void)
  19 {
  20         cpu_stop();
  21 }
  22
  23 bool cpu_has_hotplug(unsigned int cpu)
  24 {
  25         if (cpu_ops[cpu]->cpu_stop)
  26                 return true;
  27
  28         return false;
  29 }
  30
  31 /*
  32  * __cpu_disable runs on the processor to be shutdown.
  33  */
  34 int __cpu_disable(void)
  35 {
  36         int ret = 0;
  37         unsigned int cpu = smp_processor_id();
  38
  39         if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_stop)
  40                 return -EOPNOTSUPP;
  41
  42         if (cpu_ops[cpu]->cpu_disable)
  43                 ret = cpu_ops[cpu]->cpu_disable(cpu);
  44
  45         if (ret)
  46                 return ret;
  47
  48         remove_cpu_topology(cpu);
  49         set_cpu_online(cpu, false);
  50         irq_migrate_all_off_this_cpu();
  51
  52         return ret;
  53 }
  54
  55 /*
  56  * Called on the thread which is asking for a CPU to be shutdown.
  57  */
  58 void __cpu_die(unsigned int cpu)
  59 {
  60         int ret = 0;
  61
  62         if (!cpu_wait_death(cpu, 5)) {
  63                 pr_err("CPU %u: didn't die\n", cpu);
  64                 return;
  65         }
  66         pr_notice("CPU%u: off\n", cpu);
  67
  68         /* Verify from the firmware if the cpu is really stopped*/
  69         if (cpu_ops[cpu]->cpu_is_stopped)
  70                 ret = cpu_ops[cpu]->cpu_is_stopped(cpu);
  71         if (ret)
  72                 pr_warn("CPU%d may not have stopped: %d\n", cpu, ret);
  73 }
  74
  75 /*
  76  * Called from the idle thread for the CPU which has been shutdown.
  77  */
  78 void cpu_stop(void)
  79 {
  80         idle_task_exit();
  81
  82         (void)cpu_report_death();
  83
  84         cpu_ops[smp_processor_id()]->cpu_stop();
  85         /* It should never reach here */
  86         BUG();
  87 }