ARM virtual counter supports event stream, it can only trigger an event
when the trigger bit (the value of CNTKCTL_EL1.EVNTI) of CNTVCT_EL0 changes,
so the actual period of event stream is 2^(cntkctl_evnti + 1). For example,
when the trigger bit is 0, then virtual counter trigger an event for every
two cycles.
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
drivers/clocksource/arm_arch_timer.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 6e11c60..4140a37 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -794,10 +794,14 @@ static void arch_timer_configure_evtstream(void)
{
int evt_stream_div, pos;
- /* Find the closest power of two to the divisor */
- evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
+ /*
+ * Find the closest power of two to the divisor. As the event
+ * stream can at most be generated at half the frequency of the
+ * counter, use half the frequency when computing the divider.
+ */
+ evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ / 2;
pos = fls(evt_stream_div);
- if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
+ if ((pos == 1) || (pos > 1 && !(evt_stream_div & (1 << (pos - 2)))))
pos--;
/* enable event stream */
arch_timer_evtstrm_enable(min(pos, 15));
--
1.8.3.1
