ARM: omap: convert sched_clock() to use new infrastructure

Convert omap to use the new sched_clock() infrastructure for extending
32bit counters to full 64-bit nanoseconds.
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -839,6 +839,7 @@ config ARCH_OMAP
 	select ARCH_REQUIRE_GPIOLIB
 	select ARCH_HAS_CPUFREQ
 	select GENERIC_CLOCKEVENTS
+	select HAVE_SCHED_CLOCK
 	select ARCH_HAS_HOLES_MEMORYMODEL
 	help
 	  Support for TI's OMAP platform (OMAP1/2/3/4).

arch/arm/plat-omap/counter_32k.c

@@ -18,6 +18,8 @@
 #include <linux/io.h>
 #include <linux/sched.h>
 
+#include <asm/sched_clock.h>
+
 #include <plat/common.h>
 #include <plat/board.h>
 
@@ -110,10 +112,25 @@ static struct clocksource clocksource_32k = {
  * Returns current time from boot in nsecs. It's OK for this to wrap
  * around for now, as it's just a relative time stamp.
  */
+static DEFINE_CLOCK_DATA(cd);
+
+/*
+ * Constants generated by clocks_calc_mult_shift(m, s, 32768, NSEC_PER_SEC, 60).
+ * This gives a resolution of about 30us and a wrap period of about 36hrs.
+ */
+#define SC_MULT		4000000000u
+#define SC_SHIFT	17
+
 unsigned long long notrace sched_clock(void)
 {
-	return clocksource_cyc2ns(clocksource_32k.read(&clocksource_32k),
-				  clocksource_32k.mult, clocksource_32k.shift);
+	u32 cyc = clocksource_32k.read(&clocksource_32k);
+	return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
+}
+
+static void notrace omap_update_sched_clock(void)
+{
+	u32 cyc = clocksource_32k.read(&clocksource_32k);
+	update_sched_clock(&cd, cyc, (u32)~0);
 }
 
 /**
@@ -171,6 +188,9 @@ static int __init omap_init_clocksource_32k(void)
 
 		if (clocksource_register_hz(&clocksource_32k, 32768))
 			printk(err, clocksource_32k.name);
+
+		init_fixed_sched_clock(&cd, omap_update_sched_clock, 32,
+				       32768, SC_MULT, SC_SHIFT);
 	}
 	return 0;
 }