forked from Minki/linux
5d0cf410e9
Implement the time sources for i386 (acpi_pm, cyclone, hpet, pit, and tsc). With this patch, the conversion of the i386 arch to the generic timekeeping code should be complete. The patch should be fairly straight forward, only adding the new clocksources. [hirofumi@mail.parknet.co.jp: acpi_pm cleanup] Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Paul Mundt <lethal@linux-sh.org> Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
86 lines
1.8 KiB
C
86 lines
1.8 KiB
C
/*
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* i8253.c 8253/PIT functions
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*
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*/
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#include <linux/clocksource.h>
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#include <linux/spinlock.h>
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#include <linux/jiffies.h>
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#include <linux/sysdev.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <asm/smp.h>
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#include <asm/delay.h>
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#include <asm/i8253.h>
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#include <asm/io.h>
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#include "io_ports.h"
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DEFINE_SPINLOCK(i8253_lock);
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EXPORT_SYMBOL(i8253_lock);
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void setup_pit_timer(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&i8253_lock, flags);
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outb_p(0x34,PIT_MODE); /* binary, mode 2, LSB/MSB, ch 0 */
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udelay(10);
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outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
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udelay(10);
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outb(LATCH >> 8 , PIT_CH0); /* MSB */
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spin_unlock_irqrestore(&i8253_lock, flags);
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}
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/*
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* Since the PIT overflows every tick, its not very useful
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* to just read by itself. So use jiffies to emulate a free
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* running counter:
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*/
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static cycle_t pit_read(void)
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{
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unsigned long flags;
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int count;
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u64 jifs;
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spin_lock_irqsave(&i8253_lock, flags);
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outb_p(0x00, PIT_MODE); /* latch the count ASAP */
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count = inb_p(PIT_CH0); /* read the latched count */
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count |= inb_p(PIT_CH0) << 8;
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/* VIA686a test code... reset the latch if count > max + 1 */
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if (count > LATCH) {
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outb_p(0x34, PIT_MODE);
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outb_p(LATCH & 0xff, PIT_CH0);
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outb(LATCH >> 8, PIT_CH0);
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count = LATCH - 1;
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}
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spin_unlock_irqrestore(&i8253_lock, flags);
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jifs = jiffies_64;
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jifs -= INITIAL_JIFFIES;
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count = (LATCH-1) - count;
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return (cycle_t)(jifs * LATCH) + count;
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}
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static struct clocksource clocksource_pit = {
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.name = "pit",
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.rating = 110,
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.read = pit_read,
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.mask = (cycle_t)-1,
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.mult = 0,
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.shift = 20,
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};
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static int __init init_pit_clocksource(void)
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{
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if (num_possible_cpus() > 4) /* PIT does not scale! */
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return 0;
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clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);
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return register_clocksource(&clocksource_pit);
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}
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module_init(init_pit_clocksource);
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