3 files changed, 32 insertions, 19 deletions

diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
index d957a51435d..59dcdced6e3 100644
--- a/arch/arm/kernel/arch_timer.c
+++ b/arch/arm/kernel/arch_timer.c
@@ -22,9 +22,11 @@ static unsigned long arch_timer_read_counter_long(void)
 	return arch_timer_read_counter();
 }
 
-static u32 arch_timer_read_counter_u32(void)
+static u32 sched_clock_mult __read_mostly;
+
+static unsigned long long notrace arch_timer_sched_clock(void)
 {
-	return arch_timer_read_counter();
+	return arch_timer_read_counter() * sched_clock_mult;
 }
 
 static struct delay_timer arch_delay_timer;
@@ -37,25 +39,20 @@ static void __init arch_timer_delay_timer_register(void)
 	register_current_timer_delay(&arch_delay_timer);
 }
 
-int __init arch_timer_of_register(void)
+int __init arch_timer_arch_init(void)
 {
-	int ret;
+        u32 arch_timer_rate = arch_timer_get_rate();
 
-	ret = arch_timer_init();
-	if (ret)
-		return ret;
+	if (arch_timer_rate == 0)
+		return -ENXIO;
 
 	arch_timer_delay_timer_register();
 
-	return 0;
-}
-
-int __init arch_timer_sched_clock_init(void)
-{
-	if (arch_timer_get_rate() == 0)
-		return -ENXIO;
+	/* Cache the sched_clock multiplier to save a divide in the hot path. */
+	sched_clock_mult = NSEC_PER_SEC / arch_timer_rate;
+	sched_clock_func = arch_timer_sched_clock;
+	pr_info("sched_clock: ARM arch timer >56 bits at %ukHz, resolution %uns\n",
+		arch_timer_rate / 1000, sched_clock_mult);
 
-	setup_sched_clock(arch_timer_read_counter_u32,
-			  32, arch_timer_get_rate());
 	return 0;
 }
diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c
index bd6f56b9ec2..880584852fc 100644
--- a/arch/arm/kernel/sched_clock.c
+++ b/arch/arm/kernel/sched_clock.c
@@ -20,6 +20,7 @@ struct clock_data {
 	u64 epoch_ns;
 	u32 epoch_cyc;
 	u32 epoch_cyc_copy;
+	unsigned long rate;
 	u32 mult;
 	u32 shift;
 	bool suspended;
@@ -113,11 +114,14 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
 	u64 res, wrap;
 	char r_unit;
 
+	if (cd.rate > rate)
+		return;
+
 	BUG_ON(bits > 32);
 	WARN_ON(!irqs_disabled());
-	WARN_ON(read_sched_clock != jiffy_sched_clock_read);
 	read_sched_clock = read;
 	sched_clock_mask = (1 << bits) - 1;
+	cd.rate = rate;
 
 	/* calculate the mult/shift to convert counter ticks to ns. */
 	clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 0);
@@ -161,12 +165,19 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
 	pr_debug("Registered %pF as sched_clock source\n", read);
 }
 
-unsigned long long notrace sched_clock(void)
+static unsigned long long notrace sched_clock_32(void)
 {
 	u32 cyc = read_sched_clock();
 	return cyc_to_sched_clock(cyc, sched_clock_mask);
 }
 
+unsigned long long __read_mostly (*sched_clock_func)(void) = sched_clock_32;
+
+unsigned long long notrace sched_clock(void)
+{
+	return sched_clock_func();
+}
+
 void __init sched_clock_postinit(void)
 {
 	/*
diff --git a/arch/arm/kernel/time.c b/arch/arm/kernel/time.c
index 955d92d265e..abff4e9aaee 100644
--- a/arch/arm/kernel/time.c
+++ b/arch/arm/kernel/time.c
@@ -22,6 +22,7 @@
 #include <linux/errno.h>
 #include <linux/profile.h>
 #include <linux/timer.h>
+#include <linux/clocksource.h>
 #include <linux/irq.h>
 
 #include <asm/thread_info.h>
@@ -115,6 +116,10 @@ int __init register_persistent_clock(clock_access_fn read_boot,
 
 void __init time_init(void)
 {
-	machine_desc->init_time();
+	if (machine_desc->init_time)
+		machine_desc->init_time();
+	else
+		clocksource_of_init();
+
 	sched_clock_postinit();
 }