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>

diff --git a/arch/arm/mach-davinci/time.c b/arch/arm/mach-davinci/time.c
index 0f21c36..5d1eea0 100644 (file)
--- a/arch/arm/mach-davinci/time.c
+++ b/arch/arm/mach-davinci/time.c
@@ -272,14 +272,35 @@ 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
  */
@@ -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,