[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>

2 files changed, 9 insertions, 53 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a04f507e7f2c..1be718208704 100644
--- a/arch/arm/Kconfig
+++ b/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.
 
diff --git a/arch/arm/mach-pxa/time.c b/arch/arm/mach-pxa/time.c
index fbfa1920353d..3c4abbf31803 100644
--- a/arch/arm/mach-pxa/time.c
+++ b/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,