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authorMark Rutland <mark.rutland@arm.com>2013-01-30 17:51:26 +0000
committerMark Rutland <mark.rutland@arm.com>2013-06-07 10:20:28 +0100
commit0d651e4e65e96989f72236bf83bd4c6e55eb6ce4 (patch)
tree85897795e32a2cc107b9c8bda0b4641785b38e8d /include/clocksource
parentf793c23ebbe5afd1cabf4a42a3a297022213756f (diff)
downloadlinux-stericsson-0d651e4e65e96989f72236bf83bd4c6e55eb6ce4.tar.gz
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.h2
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