// SPDX-License-Identifier: GPL-2.0-only/* * Copyright (c) 2020 Western Digital Corporation or its affiliates. */ #include <linux/errno.h>#include <linux/of.h>#include <linux/string.h>#include <linux/sched/task_stack.h>#include <asm/cpu_ops.h>#include <asm/sbi.h>#include <asm/smp.h> #include "head.h" const struct cpu_operations cpu_ops_spinwait;void *__cpu_spinwait_stack_pointer[NR_CPUS] __section(".data");void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data"); static void cpu_update_secondary_bootdata(unsigned int cpuid,				   struct task_struct *tidle){	unsigned long hartid = cpuid_to_hartid_map(cpuid); 	/*	 * The hartid must be less than NR_CPUS to avoid out-of-bound access	 * errors for __cpu_spinwait_stack/task_pointer. That is not always possible	 * for platforms with discontiguous hartid numbering scheme. That's why	 * spinwait booting is not the recommended approach for any platforms	 * booting Linux in S-mode and can be disabled in the future.	 */	if (hartid == INVALID_HARTID || hartid >= (unsigned long) NR_CPUS)		return; 	/* Make sure tidle is updated */	smp_mb();	WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));	WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);} static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle){	/*	 * In this protocol, all cpus boot on their own accord.  _start	 * selects the first cpu to boot the kernel and causes the remainder	 * of the cpus to spin in a loop waiting for their stack pointer to be	 * setup by that main cpu.  Writing to bootdata	 * (i.e __cpu_spinwait_stack_pointer) signals to the spinning cpus that they	 * can continue the boot process.	 */	cpu_update_secondary_bootdata(cpuid, tidle); 	return 0;} const struct cpu_operations cpu_ops_spinwait = {	.cpu_start	= spinwait_cpu_start,};