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linux-next/arch/x86/include/asm/delay.h
Kyung Min Park cec5f268cd x86/delay: Introduce TPAUSE delay
TPAUSE instructs the processor to enter an implementation-dependent
optimized state. The instruction execution wakes up when the time-stamp
counter reaches or exceeds the implicit EDX:EAX 64-bit input value.
The instruction execution also wakes up due to the expiration of
the operating system time-limit or by an external interrupt
or exceptions such as a debug exception or a machine check exception.

TPAUSE offers a choice of two lower power states:
 1. Light-weight power/performance optimized state C0.1
 2. Improved power/performance optimized state C0.2

This way, it can save power with low wake-up latency in comparison to
spinloop based delay. The selection between the two is governed by the
input register.

TPAUSE is available on processors with X86_FEATURE_WAITPKG.

Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Kyung Min Park <kyung.min.park@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/1587757076-30337-4-git-send-email-kyung.min.park@intel.com
2020-05-07 16:06:20 +02:00

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C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_DELAY_H
#define _ASM_X86_DELAY_H
#include <asm-generic/delay.h>
#include <linux/init.h>
void __init use_tsc_delay(void);
void __init use_tpause_delay(void);
void use_mwaitx_delay(void);
#endif /* _ASM_X86_DELAY_H */