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4e8d76373c
The Footbridge platforms have some reasonable timers in the host bridge, which we use for most footbridge-based platforms. However, NetWinder's clock these using a spread-spectrum clock which makes them too unstable for time keeping. So we have to rely on the PIT. Convert both Footbridge timers and PIT timers to use the clocksource and clockevent infrastructure. Tested on Netwinder. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
133 lines
2.7 KiB
C
133 lines
2.7 KiB
C
/*
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* linux/arch/arm/mach-footbridge/isa-timer.c
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*
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* Copyright (C) 1998 Russell King.
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* Copyright (C) 1998 Phil Blundell
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*/
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#include <linux/clockchips.h>
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#include <linux/clocksource.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/io.h>
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#include <linux/timex.h>
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#include <asm/irq.h>
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#include <asm/mach/time.h>
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#include "common.h"
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#define PIT_MODE 0x43
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#define PIT_CH0 0x40
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#define PIT_LATCH ((PIT_TICK_RATE + HZ / 2) / HZ)
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static cycle_t pit_read(struct clocksource *cs)
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{
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unsigned long flags;
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static int old_count;
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static u32 old_jifs;
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int count;
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u32 jifs;
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raw_local_irq_save(flags);
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jifs = jiffies;
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outb_p(0x00, PIT_MODE); /* latch the count */
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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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if (count > old_count && jifs == old_jifs)
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count = old_count;
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old_count = count;
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old_jifs = jifs;
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raw_local_irq_restore(flags);
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count = (PIT_LATCH - 1) - count;
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return (cycle_t)(jifs * PIT_LATCH) + count;
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}
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static struct clocksource pit_cs = {
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.name = "pit",
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.rating = 110,
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.read = pit_read,
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.mask = CLOCKSOURCE_MASK(32),
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};
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static void pit_set_mode(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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unsigned long flags;
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raw_local_irq_save(flags);
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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outb_p(0x34, PIT_MODE);
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outb_p(PIT_LATCH & 0xff, PIT_CH0);
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outb_p(PIT_LATCH >> 8, PIT_CH0);
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break;
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case CLOCK_EVT_MODE_SHUTDOWN:
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case CLOCK_EVT_MODE_UNUSED:
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outb_p(0x30, PIT_MODE);
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outb_p(0, PIT_CH0);
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outb_p(0, PIT_CH0);
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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case CLOCK_EVT_MODE_RESUME:
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break;
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}
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local_irq_restore(flags);
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}
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static int pit_set_next_event(unsigned long delta,
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struct clock_event_device *evt)
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{
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return 0;
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}
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static struct clock_event_device pit_ce = {
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.name = "pit",
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.features = CLOCK_EVT_FEAT_PERIODIC,
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.set_mode = pit_set_mode,
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.set_next_event = pit_set_next_event,
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.shift = 32,
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};
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static irqreturn_t pit_timer_interrupt(int irq, void *dev_id)
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{
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struct clock_event_device *ce = dev_id;
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ce->event_handler(ce);
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return IRQ_HANDLED;
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}
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static struct irqaction pit_timer_irq = {
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.name = "pit",
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.handler = pit_timer_interrupt,
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.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
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.dev_id = &pit_ce,
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};
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static void __init isa_timer_init(void)
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{
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pit_ce.cpumask = cpumask_of(smp_processor_id());
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pit_ce.mult = div_sc(PIT_TICK_RATE, NSEC_PER_SEC, pit_ce.shift);
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pit_ce.max_delta_ns = clockevent_delta2ns(0x7fff, &pit_ce);
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pit_ce.min_delta_ns = clockevent_delta2ns(0x000f, &pit_ce);
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clocksource_register_hz(&pit_cs, PIT_TICK_RATE);
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setup_irq(pit_ce.irq, &pit_timer_irq);
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clockevents_register_device(&pit_ce);
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}
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struct sys_timer isa_timer = {
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.init = isa_timer_init,
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};
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