The default sched_clock provides a maximum resolution of 1 ms which
normally is not sufficient to investigate scheduling related
irregularities - more so, if a low-latency or even a real-time kernel is
used. Therefore, register the Atmel TCB clocksource that provides a
resolution of 63 ns as sched_clock.
Signed-off-by: Carsten Emde <C.Emde@xxxxxxxxx>
---
drivers/clocksource/tcb_clksrc.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
Index: linux/drivers/clocksource/tcb_clksrc.c
===================================================================
--- linux.orig/drivers/clocksource/tcb_clksrc.c
+++ linux/drivers/clocksource/tcb_clksrc.c
@@ -10,6 +10,7 @@
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/atmel_tc.h>
+#include <linux/sched_clock.h>
/*
@@ -41,6 +42,14 @@
static void __iomem *tcaddr;
+static struct clocksource clksrc = {
+ .name = "tcb_clksrc",
+ .rating = 200,
+ .read = tc_get_cycles,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
static cycle_t tc_get_cycles(struct clocksource *cs)
{
unsigned long flags;
@@ -61,13 +70,10 @@ static cycle_t tc_get_cycles32(struct cl
return __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));
}
-static struct clocksource clksrc = {
- .name = "tcb_clksrc",
- .rating = 200,
- .read = tc_get_cycles,
- .mask = CLOCKSOURCE_MASK(32),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
-};
+static u64 sched_clock_get_cycles(void)
+{
+ return (u64) do_sched_clock_get_cycles(NULL);
+}
#ifdef CONFIG_GENERIC_CLOCKEVENTS
@@ -273,6 +279,7 @@ static int __init tcb_clksrc_init(void)
int clk32k_divisor_idx = -1;
int i;
int ret;
+ unsigned long flags;
tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK);
if (!tc) {
@@ -339,6 +346,10 @@ static int __init tcb_clksrc_init(void)
if (ret)
goto err_disable_t1;
+ local_irq_save(flags);
+ sched_clock_register(sched_clock_get_cycles, 32, divided_rate);
+ local_irq_restore(flags);
+
/* channel 2: periodic and oneshot timer support */
ret = setup_clkevents(tc, clk32k_divisor_idx);
if (ret)
--
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