time.c
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/*
* arch/arm/mach-pxa/time.c
*
* PXA clocksource, clockevents, and OST interrupt handlers.
* Copyright (c) 2007 by Bill Gatliff <bgat@billgatliff.com>.
*
* Derived from Nicolas Pitre's PXA timer handler Copyright (c) 2001
* by MontaVista Software, Inc. (Nico, your code rocks!)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/clockchips.h>
#include <linux/sched_clock.h>
#include <asm/div64.h>
#include <asm/mach/irq.h>
#include <asm/mach/time.h>
#include <mach/regs-ost.h>
#include <mach/irqs.h>
/*
* This is PXA's sched_clock implementation. This has a resolution
* of at least 308 ns and a maximum value of 208 days.
*
* The return value is guaranteed to be monotonic in that range as
* long as there is always less than 582 seconds between successive
* calls to sched_clock() which should always be the case in practice.
*/
static u64 notrace pxa_read_sched_clock(void)
{
return readl_relaxed(OSCR);
}
#define MIN_OSCR_DELTA 16
static irqreturn_t
pxa_ost0_interrupt(int irq, void *dev_id)
{
struct clock_event_device *c = dev_id;
/* Disarm the compare/match, signal the event. */
writel_relaxed(readl_relaxed(OIER) & ~OIER_E0, OIER);
writel_relaxed(OSSR_M0, OSSR);
c->event_handler(c);
return IRQ_HANDLED;
}
static int
pxa_osmr0_set_next_event(unsigned long delta, struct clock_event_device *dev)
{
unsigned long next, oscr;
writel_relaxed(readl_relaxed(OIER) | OIER_E0, OIER);
next = readl_relaxed(OSCR) + delta;
writel_relaxed(next, OSMR0);
oscr = readl_relaxed(OSCR);
return (signed)(next - oscr) <= MIN_OSCR_DELTA ? -ETIME : 0;
}
static void
pxa_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *dev)
{
switch (mode) {
case CLOCK_EVT_MODE_ONESHOT:
writel_relaxed(readl_relaxed(OIER) & ~OIER_E0, OIER);
writel_relaxed(OSSR_M0, OSSR);
break;
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
/* initializing, released, or preparing for suspend */
writel_relaxed(readl_relaxed(OIER) & ~OIER_E0, OIER);
writel_relaxed(OSSR_M0, OSSR);
break;
case CLOCK_EVT_MODE_RESUME:
case CLOCK_EVT_MODE_PERIODIC:
break;
}
}
#ifdef CONFIG_PM
static unsigned long osmr[4], oier, oscr;
static void pxa_timer_suspend(struct clock_event_device *cedev)
{
osmr[0] = readl_relaxed(OSMR0);
osmr[1] = readl_relaxed(OSMR1);
osmr[2] = readl_relaxed(OSMR2);
osmr[3] = readl_relaxed(OSMR3);
oier = readl_relaxed(OIER);
oscr = readl_relaxed(OSCR);
}
static void pxa_timer_resume(struct clock_event_device *cedev)
{
/*
* Ensure that we have at least MIN_OSCR_DELTA between match
* register 0 and the OSCR, to guarantee that we will receive
* the one-shot timer interrupt. We adjust OSMR0 in preference
* to OSCR to guarantee that OSCR is monotonically incrementing.
*/
if (osmr[0] - oscr < MIN_OSCR_DELTA)
osmr[0] += MIN_OSCR_DELTA;
writel_relaxed(osmr[0], OSMR0);
writel_relaxed(osmr[1], OSMR1);
writel_relaxed(osmr[2], OSMR2);
writel_relaxed(osmr[3], OSMR3);
writel_relaxed(oier, OIER);
writel_relaxed(oscr, OSCR);
}
#else
#define pxa_timer_suspend NULL
#define pxa_timer_resume NULL
#endif
static struct clock_event_device ckevt_pxa_osmr0 = {
.name = "osmr0",
.features = CLOCK_EVT_FEAT_ONESHOT,
.rating = 200,
.set_next_event = pxa_osmr0_set_next_event,
.set_mode = pxa_osmr0_set_mode,
.suspend = pxa_timer_suspend,
.resume = pxa_timer_resume,
};
static struct irqaction pxa_ost0_irq = {
.name = "ost0",
.flags = IRQF_TIMER | IRQF_IRQPOLL,
.handler = pxa_ost0_interrupt,
.dev_id = &ckevt_pxa_osmr0,
};
void __init pxa_timer_init(void)
{
unsigned long clock_tick_rate = get_clock_tick_rate();
writel_relaxed(0, OIER);
writel_relaxed(OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3, OSSR);
sched_clock_register(pxa_read_sched_clock, 32, clock_tick_rate);
ckevt_pxa_osmr0.cpumask = cpumask_of(0);
setup_irq(IRQ_OST0, &pxa_ost0_irq);
clocksource_mmio_init(OSCR, "oscr0", clock_tick_rate, 200, 32,
clocksource_mmio_readl_up);
clockevents_config_and_register(&ckevt_pxa_osmr0, clock_tick_rate,
MIN_OSCR_DELTA * 2, 0x7fffffff);
}