David Woodhouse
c02c52036e
commit 70e6b7d9ae upstream.
Leaving the PIT interrupt running can cause noticeable steal time for
virtual guests. The VMM generally has a timer which toggles the IRQ input
to the PIC and I/O APIC, which takes CPU time away from the guest. Even
on real hardware, running the counter may use power needlessly (albeit
not much).
Make sure it's turned off if it isn't going to be used.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhkelley@outlook.com>
Link: https://lore.kernel.org/all/20240802135555.564941-1-dwmw2@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
32 lines
853 B
C
32 lines
853 B
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Machine specific IO port address definition for generic.
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* Written by Osamu Tomita <tomita@cinet.co.jp>
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*/
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#ifndef __LINUX_I8253_H
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#define __LINUX_I8253_H
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#include <linux/param.h>
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#include <linux/spinlock.h>
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#include <linux/timex.h>
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/* i8253A PIT registers */
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#define PIT_MODE 0x43
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#define PIT_CH0 0x40
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#define PIT_CH2 0x42
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#define PIT_LATCH ((PIT_TICK_RATE + HZ/2) / HZ)
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extern raw_spinlock_t i8253_lock;
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extern bool i8253_clear_counter_on_shutdown;
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extern struct clock_event_device i8253_clockevent;
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extern void clockevent_i8253_init(bool oneshot);
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extern void clockevent_i8253_disable(void);
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extern void setup_pit_timer(void);
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#endif /* __LINUX_I8253_H */
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