52 lines
1.4 KiB
C
52 lines
1.4 KiB
C
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/*
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* Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*/
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#ifndef __ASM_SIMD_H
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#define __ASM_SIMD_H
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#include <linux/compiler.h>
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#include <linux/irqflags.h>
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#include <linux/percpu.h>
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#include <linux/preempt.h>
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#include <linux/types.h>
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#ifdef CONFIG_KERNEL_MODE_NEON
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DECLARE_PER_CPU(bool, kernel_neon_busy);
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/*
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* may_use_simd - whether it is allowable at this time to issue SIMD
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* instructions or access the SIMD register file
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*
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* Callers must not assume that the result remains true beyond the next
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* preempt_enable() or return from softirq context.
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*/
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static __must_check inline bool may_use_simd(void)
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{
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/*
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* kernel_neon_busy is only set while preemption is disabled,
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* and is clear whenever preemption is enabled. Since
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* this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy
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* cannot change under our feet -- if it's set we cannot be
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* migrated, and if it's clear we cannot be migrated to a CPU
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* where it is set.
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*/
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return !in_irq() && !irqs_disabled() && !in_nmi() &&
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!this_cpu_read(kernel_neon_busy);
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}
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#else /* ! CONFIG_KERNEL_MODE_NEON */
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static __must_check inline bool may_use_simd(void) {
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return false;
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}
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#endif /* ! CONFIG_KERNEL_MODE_NEON */
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#endif
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