linux-kernel - [PATCH 2/3] clocksource: sun4i: Report the minimum tick that we can program

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Message-Id: <1381777668-32565-3-git-send-email-maxime.ripard@free-electrons.com>
Date:	Mon, 14 Oct 2013 21:07:47 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	daniel.lezcano@...aro.org, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: [PATCH 2/3] clocksource: sun4i: Report the minimum tick that we can program

We need to wait for at least 2 clock cycles whenever we reprogram our
clockevent timer. Report that the minimum number of ticks we can handle
is 3 ticks, and remove 3 ticks to the interval programmed to reflect
this.

Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
---
 drivers/clocksource/sun4i_timer.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/sun4i_timer.c b/drivers/clocksource/sun4i_timer.c
index 8ead025..46008f9 100644
--- a/drivers/clocksource/sun4i_timer.c
+++ b/drivers/clocksource/sun4i_timer.c
@@ -37,6 +37,8 @@
 #define TIMER_INTVAL_REG(val)	(0x10 * (val) + 0x14)
 #define TIMER_CNTVAL_REG(val)	(0x10 * (val) + 0x18)
 
+#define TIMER_SYNC_TICKS	3
+
 static void __iomem *timer_base;
 static u32 ticks_per_jiffy;
 
@@ -50,7 +52,7 @@ static void sun4i_clkevt_sync(void)
 {
 	u32 old = readl(timer_base + TIMER_CNTVAL_REG(1));
 
-	while ((old - readl(timer_base + TIMER_CNTVAL_REG(1))) < 3)
+	while ((old - readl(timer_base + TIMER_CNTVAL_REG(1))) < TIMER_SYNC_TICKS)
 		cpu_relax();
 }
 
@@ -104,7 +106,7 @@ static int sun4i_clkevt_next_event(unsigned long evt,
 				   struct clock_event_device *unused)
 {
 	sun4i_clkevt_time_stop(0);
-	sun4i_clkevt_time_setup(0, evt);
+	sun4i_clkevt_time_setup(0, evt - TIMER_SYNC_TICKS);
 	sun4i_clkevt_time_start(0, false);
 
 	return 0;
@@ -187,8 +189,8 @@ static void __init sun4i_timer_init(struct device_node *node)
 
 	sun4i_clockevent.cpumask = cpumask_of(0);
 
-	clockevents_config_and_register(&sun4i_clockevent, rate, 0x1,
-					0xffffffff);
+	clockevents_config_and_register(&sun4i_clockevent, rate,
+					TIMER_SYNC_TICKS, 0xffffffff);
 }
 CLOCKSOURCE_OF_DECLARE(sun4i, "allwinner,sun4i-timer",
 		       sun4i_timer_init);
-- 
1.8.4

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