diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2013-01-30 17:51:26 +0000 |
|---|---|---|
| committer | Mark Brown <broonie@linaro.org> | 2014-05-14 12:17:21 +0100 |
| commit | 66effa189f8ded4d968dd9c310137c50244477ad (patch) | |
| tree | 965f0fe518e66a503b87436137d46188619fdfaa /include/clocksource/arm_arch_timer.h | |
| parent | 833b6f7f66c2343e1b23dd8d35c12324d70a6731 (diff) | |
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>
Diffstat (limited to 'include/clocksource/arm_arch_timer.h')
| -rw-r--r-- | include/clocksource/arm_arch_timer.h | 2 |
1 files changed, 1 insertions, 1 deletions
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 |