linux-kernel - [PATCH] [PATCH] clocksource: tcb: fix min

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Date:	Fri, 13 Sep 2013 15:02:45 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	kernel@...gutronix.de, nicolas.ferre@...el.com,
	john.stultz@...aro.org, linux-arm-kernel@...ts.infradead.org,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Marc Pignat <marc.pignat@...s.ch>,
	Ronald Wahl <ronald.wahl@...itan.com>
Subject: [PATCH] [PATCH] clocksource: tcb: fix min_delta calculation

The commit

    77cc982 clocksource: use clockevents_config_and_register() where possible

switches from manually calculating min_delta_ns (and others) and
clockevents_register_device() to automatic calculation via
clockevents_config_and_register(). During this conversation the "+ 1" in

    min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;

was lost. This leads to problems when programming clock events, resuling in
e.g. a sleep(2) sleeping more than 3 seconds. The "+ 1" was added in the
original code to fix a rounding problem in clockevent_delta2ns(), see
http://permalink.gmane.org/gmane.linux.kernel/549744 for background
information.

This patch fixes the problem by increasing the min_delta to "2" ticks.

Cc: Marc Pignat <marc.pignat@...s.ch>
Cc: Ronald Wahl <ronald.wahl@...itan.com>
Acked-by: Shawn Guo <shawn.guo@...aro.org>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
Changes since v1:
- Improved description. Thanks to Ronald Wahl.

 drivers/clocksource/tcb_clksrc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
index 8a61872..7cf6dc7 100644
--- a/drivers/clocksource/tcb_clksrc.c
+++ b/drivers/clocksource/tcb_clksrc.c
@@ -197,7 +197,7 @@ static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 
 	clkevt.clkevt.cpumask = cpumask_of(0);
 
-	clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
+	clockevents_config_and_register(&clkevt.clkevt, 32768, 2, 0xffff);
 
 	setup_irq(irq, &tc_irqaction);
 }
-- 
1.8.4.rc3

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