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authorMark Rutland <mark.rutland@arm.com>2013-01-30 17:51:26 +0000
committerMark Brown <broonie@linaro.org>2014-05-14 12:17:21 +0100
commit66effa189f8ded4d968dd9c310137c50244477ad (patch)
tree965f0fe518e66a503b87436137d46188619fdfaa
parent833b6f7f66c2343e1b23dd8d35c12324d70a6731 (diff)
downloadlinux-linaro-stable-66effa189f8ded4d968dd9c310137c50244477ad.tar.gz
clocksource: arch_timer: use virtual counters
commit 0d651e4e65e96989f72236bf83bd4c6e55eb6ce4 upstream. Switching between reading the virtual or physical counters is problematic, as some core code wants a view of time before we're fully set up. Using a function pointer and switching the source after the first read can make time appear to go backwards, and having a check in the read function is an unfortunate block on what we want to be a fast path. Instead, this patch makes us always use the virtual counters. If we're a guest, or don't have hyp mode, we'll use the virtual timers, and as such don't care about CNTVOFF as long as it doesn't change in such a way as to make time appear to travel backwards. As the guest will use the virtual timers, a (potential) KVM host must use the physical timers (which can wake up the host even if they fire while a guest is executing), and hence a host must have CNTVOFF set to zero so as to have a consistent view of time between the physical timers and virtual counters. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Cc: Rob Herring <rob.herring@calxeda.com> Cc: Mark Brown <broonie@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> (cherry picked from commit 714c21cb90951905b269870087a99c37f3a7af0c) Signed-off-by: Mark Brown <broonie@linaro.org>
-rw-r--r--arch/arm/include/asm/arch_timer.h9
-rw-r--r--arch/arm64/include/asm/arch_timer.h10
-rw-r--r--drivers/clocksource/arm_arch_timer.c23
-rw-r--r--include/clocksource/arm_arch_timer.h2
4 files changed, 6 insertions, 38 deletions
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index 7c1bfc0aea0c..accefe099182 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -80,15 +80,6 @@ static inline u32 arch_timer_get_cntfrq(void)
return val;
}
-static inline u64 arch_counter_get_cntpct(void)
-{
- u64 cval;
-
- isb();
- asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval));
- return cval;
-}
-
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index bf6ab242f047..d56ed11ba9a3 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -110,16 +110,6 @@ static inline void __cpuinit arch_counter_set_user_access(void)
asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
}
-static inline u64 arch_counter_get_cntpct(void)
-{
- u64 cval;
-
- isb();
- asm volatile("mrs %0, cntpct_el0" : "=r" (cval));
-
- return cval;
-}
-
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index a2b254189782..053d846ab5b1 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -186,27 +186,19 @@ u32 arch_timer_get_rate(void)
return arch_timer_rate;
}
-/*
- * Some external users of arch_timer_read_counter (e.g. sched_clock) may try to
- * call it before it has been initialised. Rather than incur a performance
- * penalty checking for initialisation, provide a default implementation that
- * won't lead to time appearing to jump backwards.
- */
-static u64 arch_timer_read_zero(void)
+u64 arch_timer_read_counter(void)
{
- return 0;
+ return arch_counter_get_cntvct();
}
-u64 (*arch_timer_read_counter)(void) = arch_timer_read_zero;
-
static cycle_t arch_counter_read(struct clocksource *cs)
{
- return arch_timer_read_counter();
+ return arch_counter_get_cntvct();
}
static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
{
- return arch_timer_read_counter();
+ return arch_counter_get_cntvct();
}
static struct clocksource clocksource_counter = {
@@ -287,7 +279,7 @@ static int __init arch_timer_register(void)
cyclecounter.mult = clocksource_counter.mult;
cyclecounter.shift = clocksource_counter.shift;
timecounter_init(&timecounter, &cyclecounter,
- arch_counter_get_cntpct());
+ arch_counter_get_cntvct());
if (arch_timer_use_virtual) {
ppi = arch_timer_ppi[VIRT_PPI];
@@ -376,11 +368,6 @@ static void __init arch_timer_init(struct device_node *np)
}
}
- if (arch_timer_use_virtual)
- arch_timer_read_counter = arch_counter_get_cntvct;
- else
- arch_timer_read_counter = arch_counter_get_cntpct;
-
arch_timer_register();
arch_timer_arch_init();
}
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index e6c9c4cc9b23..c463ce990c48 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -32,7 +32,7 @@
#ifdef CONFIG_ARM_ARCH_TIMER
extern u32 arch_timer_get_rate(void);
-extern u64 (*arch_timer_read_counter)(void);
+extern u64 arch_timer_read_counter(void);
extern struct timecounter *arch_timer_get_timecounter(void);
#else