[PATCH] drivers: arm arch timer: Correct fault programming of CNTKCTL_EL1.EVNTI

[Keqian Zhu]

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: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
 drivers/clocksource/arm_arch_timer.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index ecf7b7db2d05..bc019dd0975b 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -799,10 +799,20 @@ static void __arch_timer_setup(unsigned type,
 static void arch_timer_evtstrm_enable(int divider)
 {
 	u32 cntkctl = arch_timer_get_cntkctl();
+	int cntkctl_evnti;
+
+	/*
+	 * Note that it can only trigger an event when the trigger bit
+	 * of CNTVCT_EL0 changes, so the actual period of event stream
+	 * is 2^(cntkctl_evnti + 1).
+	 */
+	cntkctl_evnti = divider - 1;
+	cntkctl_evnti = min(cntkctl_evnti, 15);
+	cntkctl_evnti = max(cntkctl_evnti, 0);
 
 	cntkctl &= ~ARCH_TIMER_EVT_TRIGGER_MASK;
 	/* Set the divider and enable virtual event stream */
-	cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT)
+	cntkctl |= (cntkctl_evnti << ARCH_TIMER_EVT_TRIGGER_SHIFT)
 			| ARCH_TIMER_VIRT_EVT_EN;
 	arch_timer_set_cntkctl(cntkctl);
 	arch_timer_set_evtstrm_feature();
@@ -816,10 +826,11 @@ static void arch_timer_configure_evtstream(void)
 	/* Find the closest power of two to the divisor */
 	evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
 	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));
+	arch_timer_evtstrm_enable(pos);
 }
 
 static void arch_counter_set_user_access(void)
-- 
2.19.1