xtensa: ccount based clockevent implementation

Reused some code from a preliminary implementation by Max Fillippov.

Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Chris Zankel <chris@zankel.net>

diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 0a1b95f81a32b165ae27421fbddf2423a4da4ca9..dadcf824a5cb91ca9d37bb51050d0ee3eb895abd 100644 (file)
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -6,6 +6,7 @@ config XTENSA
        select ARCH_WANT_FRAME_POINTERS
        select HAVE_IDE
        select GENERIC_ATOMIC64
+       select GENERIC_CLOCKEVENTS
        select HAVE_GENERIC_HARDIRQS
        select VIRT_TO_BUS
        select GENERIC_IRQ_SHOW

diff --git a/arch/xtensa/kernel/time.c b/arch/xtensa/kernel/time.c
index a32bc2ea7982981f8a62b67c7dde41d2c3a7427d..ece4f95886252528e3115a9ef16632d3ff758f22 100644 (file)
--- a/arch/xtensa/kernel/time.c
+++ b/arch/xtensa/kernel/time.c
@@ -16,6 +16,7 @@
 #include <linux/sched.h>
 #include <linux/time.h>
 #include <linux/clocksource.h>
+#include <linux/clockchips.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
 #include <linux/init.h>
@@ -43,16 +44,80 @@ static struct clocksource ccount_clocksource = {
        .mask = CLOCKSOURCE_MASK(32),
 };
 
+static int ccount_timer_set_next_event(unsigned long delta,
+               struct clock_event_device *dev);
+static void ccount_timer_set_mode(enum clock_event_mode mode,
+               struct clock_event_device *evt);
+static struct ccount_timer_t {
+       struct clock_event_device evt;
+       int irq_enabled;
+} ccount_timer = {
+       .evt = {
+               .name           = "ccount_clockevent",
+               .features       = CLOCK_EVT_FEAT_ONESHOT,
+               .rating         = 300,
+               .set_next_event = ccount_timer_set_next_event,
+               .set_mode       = ccount_timer_set_mode,
+       },
+};
+
+static int ccount_timer_set_next_event(unsigned long delta,
+               struct clock_event_device *dev)
+{
+       unsigned long flags, next;
+       int ret = 0;
+
+       local_irq_save(flags);
+       next = get_ccount() + delta;
+       set_linux_timer(next);
+       if (next - get_ccount() > delta)
+               ret = -ETIME;
+       local_irq_restore(flags);
+
+       return ret;
+}
+
+static void ccount_timer_set_mode(enum clock_event_mode mode,
+               struct clock_event_device *evt)
+{
+       struct ccount_timer_t *timer =
+               container_of(evt, struct ccount_timer_t, evt);
+
+       /*
+        * There is no way to disable the timer interrupt at the device level,
+        * only at the intenable register itself. Since enable_irq/disable_irq
+        * calls are nested, we need to make sure that these calls are
+        * balanced.
+        */
+       switch (mode) {
+       case CLOCK_EVT_MODE_SHUTDOWN:
+       case CLOCK_EVT_MODE_UNUSED:
+               if (timer->irq_enabled) {
+                       disable_irq(evt->irq);
+                       timer->irq_enabled = 0;
+               }
+               break;
+       case CLOCK_EVT_MODE_RESUME:
+       case CLOCK_EVT_MODE_ONESHOT:
+               if (!timer->irq_enabled) {
+                       enable_irq(evt->irq);
+                       timer->irq_enabled = 1;
+               }
+       default:
+               break;
+       }
+}
+
 static irqreturn_t timer_interrupt(int irq, void *dev_id);
 static struct irqaction timer_irqaction = {
        .handler =      timer_interrupt,
-       .flags =        IRQF_DISABLED,
+       .flags =        IRQF_TIMER,
        .name =         "timer",
+       .dev_id =       &ccount_timer,
 };
 
 void __init time_init(void)
 {
-       unsigned int irq;
 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
        printk("Calibrating CPU frequency ");
        platform_calibrate_ccount();
@@ -61,11 +126,14 @@ void __init time_init(void)
 #endif
        clocksource_register_hz(&ccount_clocksource, CCOUNT_PER_JIFFY * HZ);
 
-       /* Initialize the linux timer interrupt. */
-
-       irq = irq_create_mapping(NULL, LINUX_TIMER_INT);
-       setup_irq(irq, &timer_irqaction);
-       set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
+       ccount_timer.evt.cpumask = cpumask_of(0);
+       ccount_timer.evt.irq = irq_create_mapping(NULL, LINUX_TIMER_INT);
+       if (WARN(!ccount_timer.evt.irq, "error: can't map timer irq"))
+               return;
+       clockevents_config_and_register(&ccount_timer.evt, ccount_freq, 0xf,
+                       0xffffffff);
+       setup_irq(ccount_timer.evt.irq, &timer_irqaction);
+       ccount_timer.irq_enabled = 1;
 }
 
 /*
@@ -74,36 +142,14 @@ void __init time_init(void)
 
 irqreturn_t timer_interrupt (int irq, void *dev_id)
 {
+       struct ccount_timer_t *timer = dev_id;
+       struct clock_event_device *evt = &timer->evt;
 
-       unsigned long next;
-
-       next = get_linux_timer();
-
-again:
-       while ((signed long)(get_ccount() - next) > 0) {
-
-               profile_tick(CPU_PROFILING);
-#ifndef CONFIG_SMP
-               update_process_times(user_mode(get_irq_regs()));
-#endif
-
-               xtime_update(1); /* Linux handler in kernel/time/timekeeping */
-
-               /* Note that writing CCOMPARE clears the interrupt. */
-
-               next += CCOUNT_PER_JIFFY;
-               set_linux_timer(next);
-       }
+       evt->event_handler(evt);
 
        /* Allow platform to do something useful (Wdog). */
-
        platform_heartbeat();
 
-       /* Make sure we didn't miss any tick... */
-
-       if ((signed long)(get_ccount() - next) > 0)
-               goto again;
-
        return IRQ_HANDLED;
 }