[ARM] pxa: remove periodic mode emulation support

Apparantly, the generic time subsystem can accurately emulate periodic
mode via the one-shot support code, so we don't need our own periodic
emulation code anymore.  Just ensure that we build support for one shot
into the generic time subsystem.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -345,6 +345,7 @@ config ARCH_PXA
 	select GENERIC_GPIO
 	select GENERIC_TIME
 	select GENERIC_CLOCKEVENTS
+	select TICK_ONESHOT
 	help
 	  Support for Intel/Marvell's PXA2xx/PXA3xx processor line.
 

arch/arm/mach-pxa/time.c

@@ -59,55 +59,17 @@ unsigned long long sched_clock(void)
 }
 
 
+#define MIN_OSCR_DELTA 16
+
 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;
-		OSSR = OSSR_M0;
-		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));
-	}
+	/* Disarm the compare/match, signal the event. */
+	OIER &= ~OIER_E0;
+	OSSR = OSSR_M0;
+	c->event_handler(c);
 
 	return IRQ_HANDLED;
 }
@@ -133,14 +95,6 @@ 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);
-		OSSR = OSSR_M0;
-		OIER |= OIER_E0;
-		OSMR0 = OSCR + LATCH;
-		raw_local_irq_restore(irqflags);
-		break;
-
 	case CLOCK_EVT_MODE_ONESHOT:
 		raw_local_irq_save(irqflags);
 		OIER &= ~OIER_E0;
@@ -158,13 +112,14 @@ pxa_osmr0_set_mode(enum clock_event_mode mode, struct clock_event_device *dev)
 		break;
 
 	case CLOCK_EVT_MODE_RESUME:
+	case CLOCK_EVT_MODE_PERIODIC:
 		break;
 	}
 }
 
 static struct clock_event_device ckevt_pxa_osmr0 = {
 	.name		= "osmr0",
-	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+	.features	= CLOCK_EVT_FEAT_ONESHOT,
 	.shift		= 32,
 	.rating		= 200,
 	.cpumask	= CPU_MASK_CPU0,