Register the counter of the Periodic Interval Timer as a possible source
for sched_clock. Keep the timer running even if the related clockevent
is disabled.
This provides a better precision than the jiffies-based default. The
TCB clocksource does not work, as it is registered too late in the
initialization sequence.
Signed-off-by: Romain Izard <romain.izard....@gmail.com>
---
Changelog:
v2:
- Keep the tick counter updated when the clocksource is disabled
- Ensure that sched_clock is a 64 bit counter
drivers/clocksource/timer-atmel-pit.c | 31 ++++++++++++++++---------------
1 file changed, 16 insertions(+), 15 deletions(-)
diff --git a/drivers/clocksource/timer-atmel-pit.c
b/drivers/clocksource/timer-atmel-pit.c
index d911c5dca8f1..609892bbf9da 100644
--- a/drivers/clocksource/timer-atmel-pit.c
+++ b/drivers/clocksource/timer-atmel-pit.c
@@ -21,6 +21,7 @@
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/slab.h>
+#include <linux/sched_clock.h>
#define AT91_PIT_MR 0x00 /* Mode Register */
#define AT91_PIT_PITIEN BIT(25) /*
Timer Interrupt Enable */
@@ -44,7 +45,7 @@ struct pit_data {
void __iomem *base;
u32 cycle;
- u32 cnt;
+ u64 cnt;
unsigned int irq;
struct clk *mck;
};
@@ -77,7 +78,7 @@ static cycle_t read_pit_clk(struct clocksource *cs)
{
struct pit_data *data = clksrc_to_pit_data(cs);
unsigned long flags;
- u32 elapsed;
+ u64 elapsed;
u32 t;
raw_local_irq_save(flags);
@@ -90,15 +91,6 @@ static cycle_t read_pit_clk(struct clocksource *cs)
return elapsed;
}
-static int pit_clkevt_shutdown(struct clock_event_device *dev)
-{
- struct pit_data *data = clkevt_to_pit_data(dev);
-
- /* disable irq, leaving the clocksource active */
- pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
- return 0;
-}
-
/*
* Clockevent device: interrupts every 1/HZ (== pit_cycles * MCK/16)
*/
@@ -156,15 +148,15 @@ static irqreturn_t at91sam926x_pit_interrupt(int irq,
void *dev_id)
WARN_ON_ONCE(!irqs_disabled());
/* The PIT interrupt may be disabled, and is shared */
- if (clockevent_state_periodic(&data->clkevt) &&
- (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
+ if (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS) {
unsigned nr_ticks;
/* Get number of ticks performed before irq, and ack it */
nr_ticks = PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
do {
data->cnt += data->cycle;
- data->clkevt.event_handler(&data->clkevt);
+ if (clockevent_state_periodic(&data->clkevt))
+ data->clkevt.event_handler(&data->clkevt);
nr_ticks--;
} while (nr_ticks);
@@ -174,6 +166,13 @@ static irqreturn_t at91sam926x_pit_interrupt(int irq, void
*dev_id)
return IRQ_NONE;
}
+static struct clocksource *pit_sched_clock;
+
+static u64 pit_sched_clock_read(void)
+{
+ return read_pit_clk(pit_sched_clock);
+}
+
/*
* Set up both clocksource and clockevent support.
*/
@@ -206,6 +205,9 @@ static void __init at91sam926x_pit_common_init(struct
pit_data *data)
data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
clocksource_register_hz(&data->clksrc, pit_rate);
+ pit_sched_clock = &data->clksrc;
+ sched_clock_register(pit_sched_clock_read, bits, pit_rate);
+
/* Set up irq handler */
ret = request_irq(data->irq, at91sam926x_pit_interrupt,
IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
@@ -221,7 +223,6 @@ static void __init at91sam926x_pit_common_init(struct
pit_data *data)
data->clkevt.rating = 100;
data->clkevt.cpumask = cpumask_of(0);
- data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
data->clkevt.resume = at91sam926x_pit_resume;
data->clkevt.suspend = at91sam926x_pit_suspend;
--
2.5.0
