davinci: Implement sched_clock()

Overwrite the default implementation of sched_clock that is based on
jiffies by something more precise. This improves timestamps in ftrace.
Implementation is copied from OMAP platform code.

Signed-off-by: Andreas Gaeer <Andreas.Gaer@baslerweb.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/arch/arm/mach-davinci/time.c b/arch/arm/mach-davinci/time.c
index 0f21c36e65dd..5d1eea026635 100644
--- a/arch/arm/mach-davinci/time.c
+++ b/arch/arm/mach-davinci/time.c
@@ -272,15 +272,36 @@ static cycle_t read_cycles(struct clocksource *cs)
         return (cycles_t)timer32_read(t);
 }
 
+/*
+ * Kernel assumes that sched_clock can be called early but may not have
+ * things ready yet.
+ */
+static cycle_t read_dummy(struct clocksource *cs)
+{
+        return 0;
+}
+
+
 static struct clocksource clocksource_davinci = {
         .rating         = 300,
-        .read           = read_cycles,
+        .read           = read_dummy,
         .mask           = CLOCKSOURCE_MASK(32),
         .shift          = 24,
         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
 /*
+ * Overwrite weak default sched_clock with something more precise
+ */
+unsigned long long notrace sched_clock(void)
+{
+        const cycle_t cyc = clocksource_davinci.read(&clocksource_davinci);
+
+        return clocksource_cyc2ns(cyc, clocksource_davinci.mult,
+                                clocksource_davinci.shift);
+}
+
+/*
  * clockevent
  */
 static int davinci_set_next_event(unsigned long cycles,
@@ -377,6 +398,7 @@ static void __init davinci_timer_init(void)
         davinci_clock_tick_rate = clk_get_rate(timer_clk);
 
         /* setup clocksource */
+        clocksource_davinci.read = read_cycles;
         clocksource_davinci.name = id_to_name[clocksource_id];
         clocksource_davinci.mult =
                 clocksource_khz2mult(davinci_clock_tick_rate/1000,