arch/riscv/kernel/cpu_ops_spinwait.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2020 Western Digital Corporation or its affiliates.
   4  */
   5
   6 #include <linux/errno.h>
   7 #include <linux/of.h>
   8 #include <linux/string.h>
   9 #include <asm/cpu_ops.h>
  10 #include <asm/sbi.h>
  11 #include <asm/smp.h>
  12
  13 const struct cpu_operations cpu_ops_spinwait;
  14
  15 static int spinwait_cpu_prepare(unsigned int cpuid)
  16 {
  17         if (!cpu_ops_spinwait.cpu_start) {
  18                 pr_err("cpu start method not defined for CPU [%d]\n", cpuid);
  19                 return -ENODEV;
  20         }
  21         return 0;
  22 }
  23
  24 static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
  25 {
  26         /*
  27          * In this protocol, all cpus boot on their own accord.  _start
  28          * selects the first cpu to boot the kernel and causes the remainder
  29          * of the cpus to spin in a loop waiting for their stack pointer to be
  30          * setup by that main cpu.  Writing to bootdata
  31          * (i.e __cpu_up_stack_pointer) signals to the spinning cpus that they
  32          * can continue the boot process.
  33          */
  34         cpu_update_secondary_bootdata(cpuid, tidle);
  35
  36         return 0;
  37 }
  38
  39 const struct cpu_operations cpu_ops_spinwait = {
  40         .name           = "spinwait",
  41         .cpu_prepare    = spinwait_cpu_prepare,
  42         .cpu_start      = spinwait_cpu_start,
  43 };