From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Tue, 4 Sep 2012 18:38:49 +0100 Subject: [PATCH v4 2/2] ARM: arch_timers: register a time/cycle counter In-Reply-To: <1346780329-14451-1-git-send-email-marc.zyngier@arm.com> References: <1346780329-14451-1-git-send-email-marc.zyngier@arm.com> Message-ID: <1346780329-14451-3-git-send-email-marc.zyngier@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 --- arch/arm/include/asm/arch_timer.h | 7 +++++++ arch/arm/kernel/arch_timer.c | 25 +++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h index 62e7547..ad9b155 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 +#include #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 c4e20b69..c04c2a6 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]; -- 1.7.12