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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 <asm/mach/irq.h>
#include <asm/mach/time.h>
#include <asm/arch/pxa-regs.h>
static irqreturn_t
pxa_ost0_interrupt(int irq, void *dev_id)
{
int next_match;
struct clock_event_device *c = dev_id;
if (c->mode == CLOCK_EVT_MODE_ONESHOT) {
/* Disarm the compare/match, signal the event. */
OIER &= ~OIER_E0;
c->event_handler(c);
} else if (c->mode == CLOCK_EVT_MODE_PERIODIC) {
/* Call the event handler as many times as necessary
* to recover missed events, if any (if we update
* OSMR0 and OSCR0 is still ahead of us, we've missed
* the event). As we're dealing with that, re-arm the
* compare/match for the next event.
*
* HACK ALERT:
*
* There's a latency between the instruction that
* writes to OSMR0 and the actual commit to the
* physical hardware, because the CPU doesn't (have
* to) run at bus speed, there's a write buffer
* between the CPU and the bus, etc. etc. So if the
* target OSCR0 is "very close", to the OSMR0 load
* value, the update to OSMR0 might not get to the
* hardware in time and we'll miss that interrupt.
*
* To be safe, if the new OSMR0 is "very close" to the
* target OSCR0 value, we call the event_handler as
* though the event actually happened. According to
* Nico's comment in the previous version of this
* code, experience has shown that 6 OSCR ticks is
* "very close" but he went with 8. We will use 16,
* based on the results of testing on PXA270.
*
* To be doubly sure, we also tell clkevt via
* clockevents_register_device() not to ask for
* anything that might put us "very close".
*/
#define MIN_OSCR_DELTA 16
do {
OSSR = OSSR_M0;
next_match = (OSMR0 += LATCH);
c->event_handler(c);
} while (((signed long)(next_match - OSCR) <= MIN_OSCR_DELTA)
&& (c->mode == CLOCK_EVT_MODE_PERIODIC));
}
return IRQ_HANDLED;
}
static int
pxa_osmr0_set_next_event(unsigned long delta, struct clock_event_device *dev)
{
unsigned long irqflags;
raw_local_irq_save(irqflags);
OSMR0 = OSCR + delta;
OSSR = OSSR_M0;
OIER |= OIER_E0;
raw_local_irq_restore(irqflags);
return 0;
}
static void
pxa_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *dev)
{
unsigned long irqflags;
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
raw_local_irq_save(irqflags);
OSMR0 = OSCR + LATCH;
OSSR = OSSR_M0;
OIER |= OIER_E0;
raw_local_irq_restore(irqflags);
break;
case CLOCK_EVT_MODE_ONESHOT:
raw_local_irq_save(irqflags);
OIER &= ~OIER_E0;
raw_local_irq_restore(irqflags);
break;
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
/* initializing, released, or preparing for suspend */
raw_local_irq_save(irqflags);
OIER &= ~OIER_E0;
raw_local_irq_restore(irqflags);
break;
}
}
static struct clock_event_device ckevt_pxa_osmr0 = {
.name = "osmr0",
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.shift = 32,
.rating = 200,
.cpumask = CPU_MASK_CPU0,
.set_next_event = pxa_osmr0_set_next_event,
.set_mode = pxa_osmr0_set_mode,
};
static cycle_t pxa_read_oscr(void)
{
return OSCR;
}
static struct clocksource cksrc_pxa_oscr0 = {
.name = "oscr0",
.rating = 200,
.read = pxa_read_oscr,
.mask = CLOCKSOURCE_MASK(32),
.shift = 20,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
static struct irqaction pxa_ost0_irq = {
.name = "ost0",
.flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
.handler = pxa_ost0_interrupt,
.dev_id = &ckevt_pxa_osmr0,
};
static void __init pxa_timer_init(void)
{
OIER = 0;
OSSR = OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3;
ckevt_pxa_osmr0.mult =
div_sc(CLOCK_TICK_RATE, NSEC_PER_SEC, ckevt_pxa_osmr0.shift);
ckevt_pxa_osmr0.max_delta_ns =
clockevent_delta2ns(0x7fffffff, &ckevt_pxa_osmr0);
ckevt_pxa_osmr0.min_delta_ns =
clockevent_delta2ns(MIN_OSCR_DELTA, &ckevt_pxa_osmr0) + 1;
cksrc_pxa_oscr0.mult =
clocksource_hz2mult(CLOCK_TICK_RATE, cksrc_pxa_oscr0.shift);
setup_irq(IRQ_OST0, &pxa_ost0_irq);
clocksource_register(&cksrc_pxa_oscr0);
clockevents_register_device(&ckevt_pxa_osmr0);
}
#ifdef CONFIG_PM
static unsigned long osmr[4], oier;
static void pxa_timer_suspend(void)
{
osmr[0] = OSMR0;
osmr[1] = OSMR1;
osmr[2] = OSMR2;
osmr[3] = OSMR3;
oier = OIER;
}
static void pxa_timer_resume(void)
{
OSMR0 = osmr[0];
OSMR1 = osmr[1];
OSMR2 = osmr[2];
OSMR3 = osmr[3];
OIER = oier;
/*
* OSCR0 is the system timer, which has to increase
* monotonically until it rolls over in hardware. The value
* (OSMR0 - LATCH) is OSCR0 at the most recent system tick,
* which is a handy value to restore to OSCR0.
*/
OSCR = OSMR0 - LATCH;
}
#else
#define pxa_timer_suspend NULL
#define pxa_timer_resume NULL
#endif
struct sys_timer pxa_timer = {
.init = pxa_timer_init,
.suspend = pxa_timer_suspend,
.resume = pxa_timer_resume,
};
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