/*
- * linux/arch/arm/mach-at91/at91sam926x_time.c
+ * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
*
* Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
* Revision 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
+ * Converted to ClockSource/ClockEvents by David Brownell.
*
* 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/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
-#include <linux/sched.h>
-#include <linux/time.h>
+#include <linux/clk.h>
+#include <linux/clockchips.h>
-#include <asm/hardware.h>
-#include <asm/io.h>
#include <asm/mach/time.h>
#include <asm/arch/at91_pit.h>
#define PIT_CPIV(x) ((x) & AT91_PIT_CPIV)
#define PIT_PICNT(x) (((x) & AT91_PIT_PICNT) >> 20)
+static u32 pit_cycle; /* write-once */
+static u32 pit_cnt; /* access only w/system irq blocked */
+
+
/*
- * Returns number of microseconds since last timer interrupt. Note that interrupts
- * will have been disabled by do_gettimeofday()
- * 'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy.
+ * Clocksource: just a monotonic counter of MCK/16 cycles.
+ * We don't care whether or not PIT irqs are enabled.
*/
-static unsigned long at91sam926x_gettimeoffset(void)
+static cycle_t read_pit_clk(void)
{
- unsigned long elapsed;
- unsigned long t = at91_sys_read(AT91_PIT_PIIR);
+ unsigned long flags;
+ u32 elapsed;
+ u32 t;
+
+ raw_local_irq_save(flags);
+ elapsed = pit_cnt;
+ t = at91_sys_read(AT91_PIT_PIIR);
+ raw_local_irq_restore(flags);
+
+ elapsed += PIT_PICNT(t) * pit_cycle;
+ elapsed += PIT_CPIV(t);
+ return elapsed;
+}
+
+static struct clocksource pit_clk = {
+ .name = "pit",
+ .rating = 175,
+ .read = read_pit_clk,
+ .shift = 20,
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
- elapsed = (PIT_PICNT(t) * LATCH) + PIT_CPIV(t); /* hardware clock cycles */
- return (unsigned long)(elapsed * jiffies_to_usecs(1)) / LATCH;
+/*
+ * Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16)
+ */
+static void
+pit_clkevt_mode(enum clock_event_mode mode, struct clock_event_device *dev)
+{
+ unsigned long flags;
+
+ switch (mode) {
+ case CLOCK_EVT_MODE_PERIODIC:
+ /* update clocksource counter, then enable the IRQ */
+ raw_local_irq_save(flags);
+ pit_cnt += pit_cycle * PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
+ at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN
+ | AT91_PIT_PITIEN);
+ raw_local_irq_restore(flags);
+ break;
+ case CLOCK_EVT_MODE_ONESHOT:
+ BUG();
+ /* FALLTHROUGH */
+ case CLOCK_EVT_MODE_SHUTDOWN:
+ case CLOCK_EVT_MODE_UNUSED:
+ /* disable irq, leaving the clocksource active */
+ at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN);
+ break;
+ case CLOCK_EVT_MODE_RESUME:
+ break;
+ }
}
+static struct clock_event_device pit_clkevt = {
+ .name = "pit",
+ .features = CLOCK_EVT_FEAT_PERIODIC,
+ .shift = 32,
+ .rating = 100,
+ .cpumask = CPU_MASK_CPU0,
+ .set_mode = pit_clkevt_mode,
+};
+
+
/*
* IRQ handler for the timer.
*/
-static irqreturn_t at91sam926x_timer_interrupt(int irq, void *dev_id)
+static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
{
- volatile long nr_ticks;
- if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) { /* This is a shared interrupt */
- /* Get number to ticks performed before interrupt and clear PIT interrupt */
+ /* The PIT interrupt may be disabled, and is shared */
+ if ((pit_clkevt.mode == CLOCK_EVT_MODE_PERIODIC)
+ && (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS)) {
+ unsigned nr_ticks;
+
+ /* Get number of ticks performed before irq, and ack it */
nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
do {
- timer_tick();
+ pit_cnt += pit_cycle;
+ pit_clkevt.event_handler(&pit_clkevt);
nr_ticks--;
} while (nr_ticks);
return IRQ_HANDLED;
- } else
- return IRQ_NONE; /* not handled */
+ }
+
+ return IRQ_NONE;
}
-static struct irqaction at91sam926x_timer_irq = {
+static struct irqaction at91sam926x_pit_irq = {
.name = "at91_tick",
.flags = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
- .handler = at91sam926x_timer_interrupt
+ .handler = at91sam926x_pit_interrupt
};
-void at91sam926x_timer_reset(void)
+static void at91sam926x_pit_reset(void)
{
- /* Disable timer */
+ /* Disable timer and irqs */
at91_sys_write(AT91_PIT_MR, 0);
- /* Clear any pending interrupts */
- (void) at91_sys_read(AT91_PIT_PIVR);
+ /* Clear any pending interrupts, wait for PIT to stop counting */
+ while (PIT_CPIV(at91_sys_read(AT91_PIT_PIVR)) != 0)
+ cpu_relax();
- /* Set Period Interval timer and enable its interrupt */
- at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN);
+ /* Start PIT but don't enable IRQ */
+ at91_sys_write(AT91_PIT_MR, (pit_cycle - 1) | AT91_PIT_PITEN);
}
/*
- * Set up timer interrupt.
+ * Set up both clocksource and clockevent support.
*/
-void __init at91sam926x_timer_init(void)
+static void __init at91sam926x_pit_init(void)
{
- /* Initialize and enable the timer */
- at91sam926x_timer_reset();
+ unsigned long pit_rate;
+ unsigned bits;
+
+ /*
+ * Use our actual MCK to figure out how many MCK/16 ticks per
+ * 1/HZ period (instead of a compile-time constant LATCH).
+ */
+ pit_rate = clk_get_rate(clk_get(NULL, "mck")) / 16;
+ pit_cycle = (pit_rate + HZ/2) / HZ;
+ WARN_ON(((pit_cycle - 1) & ~AT91_PIT_PIV) != 0);
- /* Make IRQs happen for the system timer. */
- setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq);
+ /* Initialize and enable the timer */
+ at91sam926x_pit_reset();
+
+ /*
+ * Register clocksource. The high order bits of PIV are unused,
+ * so this isn't a 32-bit counter unless we get clockevent irqs.
+ */
+ pit_clk.mult = clocksource_hz2mult(pit_rate, pit_clk.shift);
+ bits = 12 /* PICNT */ + ilog2(pit_cycle) /* PIV */;
+ pit_clk.mask = CLOCKSOURCE_MASK(bits);
+ clocksource_register(&pit_clk);
+
+ /* Set up irq handler */
+ setup_irq(AT91_ID_SYS, &at91sam926x_pit_irq);
+
+ /* Set up and register clockevents */
+ pit_clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, pit_clkevt.shift);
+ clockevents_register_device(&pit_clkevt);
}
-#ifdef CONFIG_PM
-static void at91sam926x_timer_suspend(void)
+static void at91sam926x_pit_suspend(void)
{
/* Disable timer */
at91_sys_write(AT91_PIT_MR, 0);
}
-#else
-#define at91sam926x_timer_suspend NULL
-#endif
struct sys_timer at91sam926x_timer = {
- .init = at91sam926x_timer_init,
- .offset = at91sam926x_gettimeoffset,
- .suspend = at91sam926x_timer_suspend,
- .resume = at91sam926x_timer_reset,
+ .init = at91sam926x_pit_init,
+ .suspend = at91sam926x_pit_suspend,
+ .resume = at91sam926x_pit_reset,
};
-
projects / linux-2.6 / commitdiff