linux-kernel - [PATCH 3.13 03/46] clocksource: vf_pit_timer: use complement for sched

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Date:	Fri, 28 Mar 2014 10:31:47 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Stefan Agner <stefan@...er.ch>,
	Shawn Guo <shawn.guo@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	daniel.lezcano@...aro.org, linux-arm-kernel@...ts.infradead.org,
	linux@....linux.org.uk
Subject: [PATCH 3.13 03/46] clocksource: vf_pit_timer: use complement for sched_clock reading

3.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Agner <stefan@...er.ch>

commit 224aa3ed45c8735ae02bb2ecca002409fa6aa772 upstream.

Vybrids PIT register is monitonic decreasing. However, sched_clock
reading needs to be monitonic increasing. Use bitwise not to get
the complement of the clock register. This fixes the clock going
backward. Also, the clock now starts at 0 since we load the
register with the maximum value at start.

Signed-off-by: Stefan Agner <stefan@...er.ch>
Acked-by: Shawn Guo <shawn.guo@...aro.org>
Cc: daniel.lezcano@...aro.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux@....linux.org.uk
Link: http://lkml.kernel.org/r/d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/clocksource/vf_pit_timer.c
+++ b/drivers/clocksource/vf_pit_timer.c
@@ -54,7 +54,7 @@ static inline void pit_irq_acknowledge(v
 
 static u64 pit_read_sched_clock(void)
 {
-	return __raw_readl(clksrc_base + PITCVAL);
+	return ~__raw_readl(clksrc_base + PITCVAL);
 }
 
 static int __init pit_clocksource_init(unsigned long rate)


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