diff options
author | Mark Rutland <mark.rutland@arm.com> | 2013-01-30 12:51:26 -0500 |
---|---|---|
committer | Mark Rutland <mark.rutland@arm.com> | 2013-06-07 05:20:28 -0400 |
commit | 0d651e4e65e96989f72236bf83bd4c6e55eb6ce4 (patch) | |
tree | 85897795e32a2cc107b9c8bda0b4641785b38e8d /include/clocksource | |
parent | f793c23ebbe5afd1cabf4a42a3a297022213756f (diff) |
clocksource: arch_timer: use virtual counters
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>
Diffstat (limited to 'include/clocksource')
-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 @@ | |||
32 | #ifdef CONFIG_ARM_ARCH_TIMER | 32 | #ifdef CONFIG_ARM_ARCH_TIMER |
33 | 33 | ||
34 | extern u32 arch_timer_get_rate(void); | 34 | extern u32 arch_timer_get_rate(void); |
35 | extern u64 (*arch_timer_read_counter)(void); | 35 | extern u64 arch_timer_read_counter(void); |
36 | extern struct timecounter *arch_timer_get_timecounter(void); | 36 | extern struct timecounter *arch_timer_get_timecounter(void); |
37 | 37 | ||
38 | #else | 38 | #else |