linux-kernel - [PATCH] clocksource: vf_pit_timer: use complement for sched

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Message-Id: <d25af915993aec1b486be653eb86f748ddef54fe.1394057313.git.stefan@agner.ch>
Date:	Wed,  5 Mar 2014 23:11:08 +0100
From:	Stefan Agner <stefan@...er.ch>
To:	daniel.lezcano@...aro.org, tglx@...utronix.de,
	shawn.guo@...aro.org, linux@....linux.org.uk
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Stefan Agner <stefan@...er.ch>
Subject: [PATCH] clocksource: vf_pit_timer: use complement for sched_clock reading

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

diff --git a/drivers/clocksource/vf_pit_timer.c b/drivers/clocksource/vf_pit_timer.c
index 02821b0..a918bc4 100644
--- a/drivers/clocksource/vf_pit_timer.c
+++ b/drivers/clocksource/vf_pit_timer.c
@@ -54,7 +54,7 @@ static inline void pit_irq_acknowledge(void)
 
 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)
-- 
1.9.0

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