[ARM] 4507/1: pxa2xx clock_event_device
Reimplements arch/arm/mach-pxa/time.c using a clock_event_device based
on OSMR0. Tested on PXA270, linux-2.6.22+arm:pxa patches.
Signed-off-by: Bill Gatliff <bgat@billgatliff.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-pxa/time.c b/arch/arm/mach-pxa/time.c
index 6f91fd2..98d27e6 100644
--- a/arch/arm/mach-pxa/time.c
+++ b/arch/arm/mach-pxa/time.c
@@ -1,9 +1,11 @@
/*
* arch/arm/mach-pxa/time.c
*
- * Author: Nicolas Pitre
- * Created: Jun 15, 2001
- * Copyright: MontaVista Software Inc.
+ * 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
@@ -12,164 +14,160 @@
#include <linux/kernel.h>
#include <linux/init.h>
-#include <linux/delay.h>
#include <linux/interrupt.h>
-#include <linux/time.h>
-#include <linux/signal.h>
-#include <linux/errno.h>
-#include <linux/sched.h>
-#include <linux/clocksource.h>
+#include <linux/clockchips.h>
-#include <asm/system.h>
-#include <asm/hardware.h>
-#include <asm/io.h>
-#include <asm/leds.h>
-#include <asm/irq.h>
#include <asm/mach/irq.h>
#include <asm/mach/time.h>
#include <asm/arch/pxa-regs.h>
-
-static int pxa_set_rtc(void)
-{
- unsigned long current_time = xtime.tv_sec;
-
- if (RTSR & RTSR_ALE) {
- /* make sure not to forward the clock over an alarm */
- unsigned long alarm = RTAR;
- if (current_time >= alarm && alarm >= RCNR)
- return -ERESTARTSYS;
- }
- RCNR = current_time;
- return 0;
-}
-
-#ifdef CONFIG_NO_IDLE_HZ
-static unsigned long initial_match;
-static int match_posponed;
-#endif
-
static irqreturn_t
-pxa_timer_interrupt(int irq, void *dev_id)
+pxa_ost0_interrupt(int irq, void *dev_id)
{
int next_match;
+ struct clock_event_device *c = dev_id;
- write_seqlock(&xtime_lock);
-
-#ifdef CONFIG_NO_IDLE_HZ
- if (match_posponed) {
- match_posponed = 0;
- OSMR0 = initial_match;
- }
-#endif
-
- /* Loop until we get ahead of the free running timer.
- * This ensures an exact clock tick count and time accuracy.
- * Since IRQs are disabled at this point, coherence between
- * lost_ticks(updated in do_timer()) and the match reg value is
- * ensured, hence we can use do_gettimeofday() from interrupt
- * handlers.
- *
- * HACK ALERT: it seems that the PXA timer regs aren't updated right
- * away in all cases when a write occurs. We therefore compare with
- * 8 instead of 0 in the while() condition below to avoid missing a
- * match if OSCR has already reached the next OSMR value.
- * Experience has shown that up to 6 ticks are needed to work around
- * this problem, but let's use 8 to be conservative. Note that this
- * affect things only when the timer IRQ has been delayed by nearly
- * exactly one tick period which should be a pretty rare event.
+ 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 {
- timer_tick();
- OSSR = OSSR_M0; /* Clear match on timer 0 */
+ OSSR = OSSR_M0;
next_match = (OSMR0 += LATCH);
- } while( (signed long)(next_match - OSCR) <= 8 );
-
- write_sequnlock(&xtime_lock);
+ c->event_handler(c);
+ } while (((signed long)(next_match - OSCR) <= MIN_OSCR_DELTA)
+ && (c->mode == CLOCK_EVT_MODE_PERIODIC));
+ }
return IRQ_HANDLED;
}
-static struct irqaction pxa_timer_irq = {
- .name = "PXA Timer Tick",
- .flags = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
- .handler = pxa_timer_interrupt,
+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_get_cycles(void)
+static cycle_t pxa_read_oscr(void)
{
return OSCR;
}
-static struct clocksource clocksource_pxa = {
- .name = "pxa_timer",
+static struct clocksource cksrc_pxa_oscr0 = {
+ .name = "oscr0",
.rating = 200,
- .read = pxa_get_cycles,
+ .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)
{
- struct timespec tv;
- unsigned long flags;
+ OIER = 0;
+ OSSR = OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3;
- set_rtc = pxa_set_rtc;
+ 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;
- OIER = 0; /* disable any timer interrupts */
- OSSR = 0xf; /* clear status on all timers */
- setup_irq(IRQ_OST0, &pxa_timer_irq);
- local_irq_save(flags);
- OIER = OIER_E0; /* enable match on timer 0 to cause interrupts */
- OSMR0 = OSCR + LATCH; /* set initial match */
- local_irq_restore(flags);
+ cksrc_pxa_oscr0.mult =
+ clocksource_hz2mult(CLOCK_TICK_RATE, cksrc_pxa_oscr0.shift);
- /*
- * OSCR runs continuously on PXA and is not written to,
- * so we can use it as clock source directly.
- */
- clocksource_pxa.mult =
- clocksource_hz2mult(CLOCK_TICK_RATE, clocksource_pxa.shift);
- clocksource_register(&clocksource_pxa);
+ setup_irq(IRQ_OST0, &pxa_ost0_irq);
+
+ clocksource_register(&cksrc_pxa_oscr0);
+ clockevents_register_device(&ckevt_pxa_osmr0);
}
-#ifdef CONFIG_NO_IDLE_HZ
-static int pxa_dyn_tick_enable_disable(void)
-{
- /* nothing to do */
- return 0;
-}
-
-static void pxa_dyn_tick_reprogram(unsigned long ticks)
-{
- if (ticks > 1) {
- initial_match = OSMR0;
- OSMR0 = initial_match + ticks * LATCH;
- match_posponed = 1;
- }
-}
-
-static irqreturn_t
-pxa_dyn_tick_handler(int irq, void *dev_id)
-{
- if (match_posponed) {
- match_posponed = 0;
- OSMR0 = initial_match;
- if ( (signed long)(initial_match - OSCR) <= 8 )
- return pxa_timer_interrupt(irq, dev_id);
- }
- return IRQ_NONE;
-}
-
-static struct dyn_tick_timer pxa_dyn_tick = {
- .enable = pxa_dyn_tick_enable_disable,
- .disable = pxa_dyn_tick_enable_disable,
- .reprogram = pxa_dyn_tick_reprogram,
- .handler = pxa_dyn_tick_handler,
-};
-#endif
-
#ifdef CONFIG_PM
static unsigned long osmr[4], oier;
@@ -191,7 +189,10 @@
OIER = oier;
/*
- * OSMR0 is the system timer: make sure OSCR is sufficiently behind
+ * 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;
}
@@ -204,7 +205,4 @@
.init = pxa_timer_init,
.suspend = pxa_timer_suspend,
.resume = pxa_timer_resume,
-#ifdef CONFIG_NO_IDLE_HZ
- .dyn_tick = &pxa_dyn_tick,
-#endif
};