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authorMarc Zyngier <Marc.Zyngier@arm.com>2012-09-07 18:09:58 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-09-15 21:53:33 +0100
commita1b2dde70419ae947fd7c9c8fcad7da005dc600e (patch)
treecf8651233dbb03cd3ce4ad891f4c40aabf2fe8a1
parentf48b5f12799dbabba4a9c799a9bef0775b2f977d (diff)
downloadlinux-linaro-stable-a1b2dde70419ae947fd7c9c8fcad7da005dc600e.tar.gz
ARM: 7522/1: arch_timers: register a time/cycle counter
Some subsystems (KVM for example) need access to a cycle counter. In the KVM case, this is used to measure the time delta between host and guest in order to accurately generate timer events for the guest. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r--arch/arm/include/asm/arch_timer.h7
-rw-r--r--arch/arm/kernel/arch_timer.c25
2 files changed, 32 insertions, 0 deletions
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index 62e75475e57e..ad9b155c8262 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -2,11 +2,13 @@
#define __ASMARM_ARCH_TIMER_H
#include <asm/errno.h>
+#include <linux/clocksource.h>
#ifdef CONFIG_ARM_ARCH_TIMER
#define ARCH_HAS_READ_CURRENT_TIMER
int arch_timer_of_register(void);
int arch_timer_sched_clock_init(void);
+struct timecounter *arch_timer_get_timecounter(void);
#else
static inline int arch_timer_of_register(void)
{
@@ -17,6 +19,11 @@ static inline int arch_timer_sched_clock_init(void)
{
return -ENXIO;
}
+
+static inline struct timecounter *arch_timer_get_timecounter(void)
+{
+ return NULL;
+}
#endif
#endif
diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
index c4e20b69197a..c04c2a6da470 100644
--- a/arch/arm/kernel/arch_timer.c
+++ b/arch/arm/kernel/arch_timer.c
@@ -333,6 +333,15 @@ int read_current_timer(unsigned long *timer_val)
return 0;
}
+static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
+{
+ /*
+ * Always use the physical counter for the clocksource.
+ * CNTHCTL.PL1PCTEN must be set to 1.
+ */
+ return arch_counter_get_cntpct();
+}
+
static struct clocksource clocksource_counter = {
.name = "arch_sys_counter",
.rating = 400,
@@ -341,6 +350,18 @@ static struct clocksource clocksource_counter = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
+static struct cyclecounter cyclecounter = {
+ .read = arch_counter_read_cc,
+ .mask = CLOCKSOURCE_MASK(56),
+};
+
+static struct timecounter timecounter;
+
+struct timecounter *arch_timer_get_timecounter(void)
+{
+ return &timecounter;
+}
+
static void __cpuinit arch_timer_stop(struct clock_event_device *clk)
{
pr_debug("arch_timer_teardown disable IRQ%d cpu #%d\n",
@@ -380,6 +401,10 @@ static int __init arch_timer_register(void)
}
clocksource_register_hz(&clocksource_counter, arch_timer_rate);
+ cyclecounter.mult = clocksource_counter.mult;
+ cyclecounter.shift = clocksource_counter.shift;
+ timecounter_init(&timecounter, &cyclecounter,
+ arch_counter_get_cntpct());
if (arch_timer_use_virtual) {
ppi = arch_timer_ppi[VIRT_PPI];