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