| 1 | |
| 2 | |
| 3 | * Copyright (c) 2020 Western Digital Corporation or its affiliates.
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| 4 |
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| 5 |
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| 6 | #include <linux/errno.h>
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| 7 | #include <linux/of.h>
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| 8 | #include <linux/string.h>
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| 9 | #include <linux/sched/task_stack.h>
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| 10 | #include <asm/cpu_ops.h>
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| 11 | #include <asm/sbi.h>
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| 12 | #include <asm/smp.h>
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| 13 |
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| 14 | #include "head.h"
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| 15 |
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| 16 | const struct cpu_operations cpu_ops_spinwait;
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| 17 | void *__cpu_spinwait_stack_pointer[NR_CPUS] __section(".data");
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| 18 | void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data");
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| 19 |
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| 20 | static void cpu_update_secondary_bootdata(unsigned int cpuid,
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| 21 | struct task_struct *tidle)
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| 22 | {
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| 23 | unsigned long hartid = cpuid_to_hartid_map(cpuid);
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| 24 |
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| 25 | |
| 26 | * The hartid must be less than NR_CPUS to avoid out-of-bound access
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| 27 | * errors for __cpu_spinwait_stack/task_pointer. That is not always possible
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| 28 | * for platforms with discontiguous hartid numbering scheme. That's why
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| 29 | * spinwait booting is not the recommended approach for any platforms
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| 30 | * booting Linux in S-mode and can be disabled in the future.
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| 31 |
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| 32 | if (hartid == INVALID_HARTID || hartid >= (unsigned long) NR_CPUS)
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| 33 | return;
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| 34 |
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| 35 |
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| 36 | smp_mb();
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| 37 | WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));
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| 38 | WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
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| 39 | }
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| 40 |
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| 41 | static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
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| 42 | {
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| 43 | |
| 44 | * In this protocol, all cpus boot on their own accord. _start
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| 45 | * selects the first cpu to boot the kernel and causes the remainder
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| 46 | * of the cpus to spin in a loop waiting for their stack pointer to be
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| 47 | * setup by that main cpu. Writing to bootdata
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| 48 | * (i.e __cpu_spinwait_stack_pointer) signals to the spinning cpus that they
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| 49 | * can continue the boot process.
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| 50 |
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| 51 | cpu_update_secondary_bootdata(cpuid, tidle);
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| 52 |
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| 53 | return 0;
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| 54 | }
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| 55 |
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| 56 | const struct cpu_operations cpu_ops_spinwait = {
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| 57 | .cpu_start = spinwait_cpu_start,
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| 58 | };
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