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
13const struct cpu_operations cpu_ops_spinwait;
14
15static 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
24static 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
39const struct cpu_operations cpu_ops_spinwait = {
40	.name		= "spinwait",
41	.cpu_prepare	= spinwait_cpu_prepare,
42	.cpu_start	= spinwait_cpu_start,
43};